Benzene Benzene A Shining Molecule The hydrocarbon that we now call benzene was first isolated in 1825 by Michael Faraday from an oily film that deposited from the gas used for lighting. Faraday did some experiments, and discovered that the new compound had equal numbers of carbons and hydrogens, and so named it 'carbureted hydrogen'. Another chemist, Laurent, proposed that due to it being discovered in illuminating gas, it should instead be called pheno, from the Greek phainein, meaning to shine. This name never really gained acceptance, but persists to this day as phenyl - the name for the C6H5- group. Michael Faraday - the discoverer of benzene Nine years after its discovery, another chemist, Mitscherlich, found he could produce the same substance by heating a chemical that had been isolated from gum benzoin - so he decided to call the compound benzin. Other chemists rejected this name because it implied the compound was similar to alkaloids, such as quinine. Another suggestion was the German name, benzol, from the German öl, meaning oil.

But in France and England the name benzene was used instead, to avoid the -ol ending confusing it with an alcohol. The Bonding Enigma The fact that benzene had a formula (C6H6) that suggested a polyene structure (i.e. many double- or triple-bonds), but did not behave at all like the other polyenes was an enigma for 19th Century chemists. In fact, whereas all the other known polyenes (e.g. butadiene) were highly reactive, benzene was remarkably inert. It became increasingly clear that there was something fundamentally different about benzene, and the family of related molecules that were gradually being synthesised from it. Because of their characteristic smells, these relatively inert, benzene-like compounds became known as aromatic compounds. The Kekulé Structure In 1865, Kekulé suggested that the structure of benzene was a regular hexagon with a hydrogen at each corner. "My mental eye..could now distinguish larger structures of manifold conformations; long rows, sometimes more closely fitted together; all twisting and turning in snake-like motion. But look! What was that? One of the snakes had seized hold of its own tail...".

Later on he modified this theory to treat benzene as a mixture of cyclohexatrienes in rapid equilibrium: "...the form whirled mockingly before my eyes...". Cyclohexatriene But such a structure should be highly reactive, and so didn't account for the unreactive nature of benzene. Other structures that were proposed at the time were Armstrong's centroid structure and Ladenburg's prismane. Armstrong's 'centroid' Ladenburg's prismane We now know that the best representation for the structure of benzene is indeed, hexagonal, with each C-C bond distance being identical, and intermediate between those for a single and double bond. The p-orbitals from each neighbouring C overlap to form a delocalised molecular orbital which extends around the ring, giving added stability and with it, decreased reactivity. delocalised p-orbitals Thus, benzene is often written as: or The extra stability that is conferred by the resonance energy makes benzene by far the most stable compared to some of the valence isomers of C6H6 shown below.

Their relative stabilities are in the order benzene > benzvalene > Dewar benzene > prismane > bicyclo-propenyl, and their energies from highest to lowest differ by almost 546 kJ/mol. Toluene and Xylene Toluene is simply benzene with an extra methyl group added to the ring, and is well-known as the precursor to TNT. It got its name because it was originally obtained from the gum of the South American tree Toluifera balsamum. This balsum, commonly called Tolu balsum, is a yellowy-brown with a pleasant aroma, and has been used in perfumes and cough syrup. On the other hand, the xylenes (from the Greek xulon for wood, since they were once obtained by distilling wood in the absence of air), have 2 methyl groups attached to the ring. There are 3 possible isomers of xylene, ortho-xylene , where the to methyls are next to each other, meta-xylene where they are separated by a hydrogen atom, and para-xylene where they are on opposite sides of the ring.

A mixture of the 3 isomers is called xylol and is often used as a solvent. Both toluene and xylene occur in gasoline (along with benzene). Their concentrations can be deliberately increased during the refining process to give a high performance BTX gasoline used for sports cars. Soft Drinks Found to Contain High Levels of Cancer-Causing Benzene Soft Drinks Found to Contain High Levels of Cancer-Causing Benzene March 2, 2006 Soft Drinks Found to Have High Levels of Cancer Chemical by Rajeev Syal Traces of a carcinogenic chemical have been found in soft drinks at eight times the level permitted in drinking water, it was revealed last night. Tests conducted on 230 drinks on sale in Britain and France have identified high levels of benzene, a compound known to cause cancer, according to the Food Standards Agency. There is a legal limit of one part per billion of benzene in British drinking water. The latest tests revealed levels of up to eight parts per billion in some soft drinks. Benzene has been linked to leukaemia and other cancers of the blood.

Traces found in Perrier water 15 years ago led to the withdrawal of more than 160 million bottles worldwide. The disclosure has prompted food safety campaigners to demand that the Government reveal which products contain benzene. At present, the drinks¹ identities have not been revealed. Richard Watts, of Sustain, a pressure group lobbying for better food standards, said that this should be done urgently because the drinks were being marketed to children. ³The scientific evidence is unclear about whether there is any safe level of benzene. We see no reason why it should be different from the designated safe level in drinking water. If it is unsafe in drinking water, why should it be safe in soft drinks?² he said. The Food Standards Agency, the government watchdog, said that the products did not pose an immediate health risk, but called for further investigation from the British drinks industry. ³Let¹s have further investigations and regular discussions with the drinks industry to check what is happening. If levels are high then the FSA will take action to protect consumers,² an agency spokesman said.

Food scientists believe that high levels of benzene may have been produced by the reaction of two commonly used ingredients  sodium benzoate, a preservative, and ascorbic acid (vitamin C). Sodium benzoate is widely used in the drinks sector. In Britain, it is used in Britvic brands including Britvic 55 apple and orange flavours, Pennine Spring flavoured waters and Shandy Bass.It is not known if any of these products were included in the latest tests. A spokesman for Britvic has previously expressed confidence in its products. A spokesman for the British Soft Drinks Association said yesterday that the industry was working to reduce the levels of benzene in soft drinks. ³There is an obligation on the industry to have as low a level of benzene as possible and we are looking at ways of reducing the levels  and maybe even removing the preservative  if we can replace it with something else,² he said. When minuscule traces of benzene were discovered in Perrier water 15 years ago, it forced the French company to withdraw millions of bottles. Tests have been carried out in Europe after US food watchdogs found benzene in juices and sodas.

The Food and Drug Administration registered its concern about the possible long-term effects on health. Professor Glenn Lawrence, of Long Island University, who first conducted tests for benzene in soft drinks 13 years ago, said that the combination of sodium benzoate and vitamin C was commonly used in drinks in the early 1990s. He said that drinks firms were now putting vitamin C back into drinks to encourage consumers to buy the product. He said that this was being done to encourage parents to buy the drinks to improve their children¹s health but it might just be doing the opposite. BENZENE FACTS * Michael Faraday discovered benzene in 1825 when he isolated it from oil gas to form a chemical, six parts carbon, six parts hydrogen * It is produced during incomplete combustion of carbon-rich substances: it is produced from petrochemicals, but occurs naturally in volcanoes, forest fires and in cigarette smoke * In the 19th and early 20th centuries it was used in aftershave, for its pleasant smell, and to decaffinate coffee.

It is now used as an anti-knock agent in petrol * It is an aggressive carcinogen and may lead to leukaemia and other cancers of the blood * In 1993, Professor Glenn Lawrence, of Long Island University, published research showing that the sodium benzoate and vitamin C found in soft drinks could react to form benzene. He suggested that drink companies were putting vitamin C into drinks to encourage customers to buy them Copyright 2006 Times Newspapers Ltd. FDA finds benzene in soft drinks BY DAVID GOLDSTEIN Knight Ridder Newspapers WASHINGTON - When small amounts of benzene, a known cancer-causing chemical, were found in some soft drinks 16 years ago, the Food and Drug Administration never told the public. That's because the beverage industry told the government it would handle the problem and the FDA thought the problem was solved. A decade and a half later, benzene has turned up again. The FDA has found levels in some soft drinks higher than what it found in 1990, and two to four times higher than what's considered safe for drinking water. Both the FDA and the beverage industry said the amounts were small and that the problem didn't appear to be widespread.

"People shouldn't overreact," said Kevin Keane, a spokesman for the American Beverage Association. "It's a very small number of products and not major brands." "The issue here is not something that should cause anyone alarm or terrific concern," said George Pauli, a top food safety expert at the FDA, "but if there's something that can be reduced, we want to reduce it." Neither Keane nor Pauli would identify the drinks being tested because the investigation is still under way. Pauli said that people ingest more benzene by breathing than they would if they drank a can of soda containing the chemical. Small amounts of the chemical also are naturally present in some foods such as fruits, vegetables and dairy products. Still, Pauli added, "You want to avoid it in any degree you can." Of the 60 or so varieties of sodas, sports drinks, juice drinks and bottled waters that the FDA has tested so far, benzene levels have ranged from two and three parts per billion to more than 10-20 parts per billion. The Environmental Protection Agency's safety standard for benzene in drinking water is five parts per billion. If it exceeds that, authorities are required to notify the public.

Keane said it was "tough to compare" the safety standard for water with soft drinks because the water rule is based on the fact that people drink more water each day. Benzene is an industrial chemical that's found in tobacco smoke, car exhaust and vapors from household products such as paint, detergents and furniture wax. Long-term exposure can cause leukemia and other cancers of the blood, according to the Centers for Disease Control and Prevention. Benzene can show up in soft drinks when two common ingredients react: ascorbic acid, otherwise known as vitamin C, and either sodium benzoate or potassium benzoate. Both are preservatives used to prevent the growth of bacteria. But the presence of these chemicals doesn't necessarily produce benzene. "It's not as simple as looking at the label, and if you see those two, there will be problems," Keane said. Pauli said that a catalyst such as temperature or light is needed to trigger the formation of benzene. That's what scientists suspect occurred in 1990 when authorities found benzene in products made by Cadbury Schweppes and Koala Springs, an Australian beverage company.

But a health safety watchdog organization said the FDA should inform the public, particularly since so many soft drinks are marketed to children. "Most people would prefer there are no known human carcinogens in what they drink," said Jane Houlihan, vice president for research at the Environmental Working Group, a nonprofit, nonpartisan scientific research group that studies toxic chemicals. "This is a case where industry agreed to get it out of the products, and all the evidence says they didn't." Soft drink manufacturers PepsiCo and Coca-Cola declined to comment and referred calls to the American Beverage Association. When benzene first turned up 16 years ago, FDA officials met with representatives of the beverage industry who "expressed their concern about the presence of benzene traces in their products and the potential for adverse publicity associated with this problem," according to an internal FDA memo from December 1990. Keane said the industry told the FDA that it was reformulating its products to alleviate the problem. Adding sugar, for instance, or replacing the vitamin C, can inhibit the chemical reaction that produces benzene, Pauli said.

An FDA official who asked not to be identified said that the agency didn't inform the public about the benzene problem 16 years ago because it didn't consider it a public health concern since the levels were low and the companies were reformulating. He said the FDA conducted follow-up testing in the early 1990s, but not since because "we thought the problem was gone and over. Then it resurfaced." The current investigation began when an activist concerned about soft drink machines in schools tried to get the FDA interested in the issue. He then sent lab results showing some soft drinks with higher-than-normal benzene levels. "Our first reaction was, `Yes, we looked at this in 1990 and essentially there was nothing there,'" Pauli said. "Then he came up with some numbers and we said, `That's not what we came up with back then. We have to go back and look.'" Asked why the problem would resurface 16 years later, Keane said the industry took the necessary steps at the time, but it's possible some manufacturers just didn't know.

"It's a very fast-growing industry, both in terms of companies and new brands, so a lot has changed in the last 16 years," he said. Food safety authorities in Great Britain and Australia also are testing soft drinks for benzene. For more information, go to: China joins soft drinks benzene probe 07/03/2006 - China has launched an inquiry into benzene in soft drinks after authorities in the UK and US found drinks containing benzene above the countries legal limits for drinking water. Chinese food safety authorities have been studying the potential for benzene residues to form in soft drinks containing ascorbic acid and sodium benzoate, according to local media reports. A public statement is expected soon. Benzene is listed as a carcinogen by public health authorities. Food safety bodies from several countries around the world have, in recent weeks, attempted to learn more about the potential for benzene formation in drinks. Their interest was sparked after the US Food and Drug Administration revealed to BeverageDaily.com it had found some drinks in the US that contained benzene above the five parts per billion legal limit for water there.

Britain's Food Standards Agency (FSA) said it would conduct its own investigation after industry testing on 230 soft drinks found average benzene levels above the UK's one part per billion limit for drinking water. The tests, done on products at the end of their shelf-life, found benzene levels up to eight parts per billion in some drinks. Benzene is listed as a known carcinogen. The FSA re-iterated that levels found to date were not a public health concern. The UK has no limit for benzene in soft drinks, and a spokesperson for the country's soft drinks association said the water limit was not applicable. Yet, a UK food legislation expert told BeverageDaily.com any court would likely look to the drinking water limit for guidance if considering benzene in soft drinks. Water is still the main ingredient in most soft drinks. A BeverageDaily investigation over the last couple of months has confirmed from several industry and government sources that benzene can form in drinks when two common ingredients  sodium benzoate and ascorbic acid (vitamin C)  react. Both the FDA and the US soft drinks industry has known this for 15 years, as testified by an internal FDA memo date January 1991.

The issue was, however, never announced to the public. The industry told the FDA it would get the word out and reformulate, according to FDA chemist Greg Diachenko. Yet, now the issue has returned. Diachenko said authorities were still evaluating results, but we certainly want to make sure there is some reformulation. The safety body has come under pressure from campaign groups in recent days to release results from its recent testing on soft drinks. It was originally alerted to the continuing presence of benzene in drinks by independent laboratory tests in New York. Results of those tests, passed on to BeverageDaily.com, show a couple of soft drinks in the US up to two-and-a-half and four times above the 10 parts per billion legal limit for drinking water set by the World Health Organisation. Perrier bottled water was recalled for containing lower levels of benzene in 1990. Kevin Keane, of the American Beverage Association (ABA), assured consumers there was no health risk, but said some brands may not be aware of the potential for sodium benzoate and ascorbic acid to form benzene. 15 years ago it was under control, but this is a fast-growing industry.

There are a lot of new companies, a lot of new brands and things have changed, ABA scientist Mike Redman said companies had learnt to control benzene formation by adjusting levels of the two ingredients in their drinks. But, Glen Lawrence, a scientist who helped the FDA with testing in 1990, said in an interview with BeverageDaily.com soft drinks firms should not use sodium benzoate and ascorbic acid together. He was concerned that producers might be adding more vitamin C into drinks as to target consumer health trends. There is no good reason to add ascorbic acid (vitamin C) to soft drinks, and those that may have ascorbic acid naturally in them (juices) should not use sodium benzoate as a preservative. So it is really very easy to avoid the problem. Lawrence co-authored a 1993 article in the Journal of Agricultural and Food Chemistry, detailing how benzene could form in the acidic conditions of drinks when sodium benzoate and ascorbic acid were present. 100 Famous Bible-Believing Scientists Engineer, mathematician, architect, inventor, 'founder' of modern science.

Nicholas Copernicus Astronomer, proposed the scientific theory of a sun-centred solar system. Tycho Brahe 1546-1601 Astronomer, produced the Rudolphine Tables (star chart), debunked the theory of heavenly spheres, proposed the Tychonic System of cosmology, introduced apparatus accuracy, record accuracy and multiple observations to astronomy, made the first complete study of a comet, proposed the extreme distance of stars, showed the non-fixity of the universe. Lord Francis Bacon Scientist, formulated the scientific method, Lord Chancellor of England. Galileo Galilei 1564-1642 Astronomer, physicist, popularised the sun-centred solar system, proved Kepler's Laws, advanced the design of telescopes, discovered sun-spots, the 4 moons of Jupiter & the phases of Venus, discovered that bodies fall with equal speed, the 'gal' geophysical unit named after him. Johann Kepler 1571-1630 Astronomer, 'founder' of physical astronomy, discovered the laws of planetary motion, established the science of celestial mechanics, published the first ephemeris tables for tracking stars, contributed to the development of calculus.

William Harvey Physician, discovered the circulation of the blood. Athanasius Kircher Inventor, studies anticipated the deciphering of Egyptian hieroglyphics & the germ theory of disease. John Wilkins Leading organizer of the scientific movement, his proteges formed the Royal Society. Walter Charleton Physician, member of the Royal Society, president of the Royal College of Physicians. Blaise Pascal 1623-1662 Mathematician, hydrostatics engineer, 'founder' of sciences of hydrostatics & hydrodynamics, laid the foundations for conic sections, differential calculus & probability theory, invented the barometer. Sir William Petty Physician, member of the Royal Society, helped found the science of statistics & also economics. Robert Boyle 1627-1691 Chemist, 'father' of modern chemistry, one of the founders of the Royal Society, discovered the gas laws, co-discovered phosphorous, invented the match, measured the density of air, first to distinguish acids/bases/neutral substances, introduced the litmus test, actively opposed alchemy.

John Ray 1627-1705 Biologist, 'father' of the sciences of biology and natural history, one of the founders of the Royal Society, greatest authority of his day on botany & zoology. Christian Huygens 1629-1695 Astronomer, mathematician, physicist, introduced the pendulum clock, developed the formula for pendulum periods, invented the telescope micrometer eye-piece, discovered the nature of Saturn's rings, proposed the wave theory of light, developed Huygen's Principle. Isaac Barrow Mathematician, Professor of Mathematics at Cambridge, taught maths to Isaac Newton. Nicholas Steno Geologist, developed the principles of stratigraphical interpretation. Robert Hooke 1635-1703 Physicist, geologist, surveyor, propounded Hooke's Law of elasticity, popularized the microscope, coined the term 'cell', invented the universal-joint & the rolling drum recorder, one of the founders of the Royal Society. Thomas Burnet Geologists, one of the first geologists. Increase Mather Astronomer, comet expert, founder of the Philosophical Society, president of Harvard.

Nehemiah Grew Physician, botanist, plant anatomy researcher, member of the Royal Society. Sir Isaac Newton 1642-1727 Physicist, discovered the laws of motion, discovered the law of gravity, invented the reflecting telescope, co-developed calculus, discovered the composition of white light, Professor of Mathematics at Cambridge, president of the Royal Society. Gottfried Wilhelm von Leibnitz 1646-1716 Mathematician, co-developer of calculus with Newton, invented the calculating machine, introduced the binary number system, anticipated the law of Conservation of Energy and Boolean logic. John Flamsteed 1646-1719 Astronomer, produced the modern star map, founded the Greenwich Observatory, the first Astronomer Royal of England. William Derham Naturalist, Boyle lecturer, some consider him the 'father' of ecology. Cotton Mather 1662-1727 Physician, president of Harvard, investigated the germ cause of smallpox, helped rid the USA of smallpox.

John Woodward 1665-1728 Physician, palaeontologist, a founding 'father' of geology, established the Cambridge Palaeontological Museum, Professor of Medicine at Gresham College (London). John Harris Mathematician, vice president of the Royal Society. William Whiston Mathematician, succeeded Sir Isaac Newton as Professor of Mathematics at Cambridge. John Hutchinson Palaeontologist, developed a strong system of natural philosophy. Carl Linnaeus 1707-1778 Physician, biologist, Professor of Medicine and also Botany at Uppsala (Sweden), established the Royal Swedish Academy of Science and was its president, developed the Linnaean classification system, 'father' of biological taxonomy, developed a cure for venereal disease, introduced the symbols for male/female. Leonhard Euler 1707-1783 Mathematician, Professor of Physics at the St Petersburg Academy of Sciences, mathematical notation, developed calculus of partial differences, developed fluid flow equations, introduced conic sections, developed fluid network theory, developed ephemeris tables for celestial bodies, introduced p , i, S and many other mathematical symbols, improved sun/moon/earth/tide calculations.

Gustavus Brander 1720-1787 Naturalist, palaeontologist, his fossil collection is in the British Museum, Fellow of the Royal Society, Trustee of the British Museum. Jean Deluc Naturalist, physicist, geologist, coined the word 'geology', invented the mercury thermometer & the hygrometer. Richard Kirwan Chemist, mineralogist, president of the Royal Irish Academy, produced the first systematic study of minerals. Sir William Herschel Astronomer, unravelled nebulae, discovered Uranus, produced the Global Star Catalogue, built giant telescopes. James Parkinson Physician, geologist, described Parkinson's disease, first to show the plant origin of coal. William Kirby Entomologist, famous for "On the History, Habits and Instincts of Animals" (subtitle). Jedidiah Morse Geographer, the leading USA geographer of his time, wrote the first USA geography textbook. Benjamin Barton Physician, botanist, zoologist, professor at Pennsylvania university, wrote the first USA botany textbook.

John Dalton 1766-1844 Chemist, meteorologist, 'father' of modern atomic theory, formulated the Law of Simple Multiple Proportions for compounds, formulated the gas Law of Partial Pressures, first to recognise and describe colour-blindness, founder of the British Association for the Advancement of Science. Georges Cuvier 1769-1832 Anatomist, vertebrate palaeontologist, 'founder' of the sciences of comparative anatomy and palaeontology, introduced phyla to systematic classification, councillor to the Imperial University (Paris), member of the Royal Society. Charles Bell 1774-1842 Surgeon, anatomist, discovered the fundamentals of nerves, 'father' of neurophysiology, Professor of Comparative Anatomy at the Royal College of Surgeons. John Kidd 1775-1851 Physician, chemist, Professor of Chemistry at Oxford, pioneered the extraction of coal chemicals, his work led to the development of synthetics.

Humphrey Davy 1778-1829 Physicist, mentor of Faraday, discovered sodium & potassium, developed the motion theory of heat (Thermokinetics), invented the mining safety lamp, developed the medical uses of laughing gas, lecturer at the Royal Institution. Benjamin Silliman 1779-1864 Geologist, chemist, 'founded' the Sheffield Scientific School at Yale, 'founder' & editor of the American Journal of Science, president of the Association of American Geologists, member of the National Academy of Sciences. Peter Mark Roget Physician, Roget's thesaurus, Professor of Physiology at the Royal Institution, secretary of the Royal Society. Sir David Brewster 1781-1868 Mineralogist, astronomer, 'founder' of optical mineralogy, invented the kaleidoscope, helped found the British Association for the Advancement of Science. William Buckland Geologist, mineralogist, Oxford professor of geology & mineralogy.

William Prout 1785-1850 Chemist, physiologist, professor, early leader in the sciences of nutrition & digestion, first to identify the major food groups, recognised that atomic weights could be a series of relative whole numbers. Adam Sedgwick Geologist, Professor of Geology at Cambridge, identified and named major rock systems. Michael Faraday 1791-1867 Chemist, physicist, proposed electric field theory, discovered the laws of electrolysis, discovered the law of electromagnetic induction (Faraday's Law), invented the transformer, dynamo, electric motor & electric generator, discovered benzene, successor to Humphrey Davy at the Royal Institution. Charles Babbage 1791-1871 Mathematician, physicist, computer pioneer, operations researcher, developed actuarial tables, invented the first computer (calculating machine), invented skeleton keys, the speedometer, the ophthalmoscope, & cow catcher, founded the Cambridge Analytical Society, member of the Royal Society, founding member of the British Association for the Advancement of Science, helped found the Royal Astronomical Society & the Statistical Society, Professor of Mathematics at Cambridge. Samuel F. B.

Morse 1791-1872 Inventor, artist, invented the telegraph & morse code, founder & president of the National Academy of Design, built the first camera in USA, made the first photographic portrait, arts professor at New York University. Sir John Herschel 1792-1871 Astronomer, physicist, meteorologist, geophysicist, expanded the global star catalogue, planned Ross' geomagnetic survey of the Antarctic, invented the cyanotype process & 'hypo' fixing in photography, made the first glass plate photograph, coined the terms 'snapshot' & 'negative'. Edward Hitchcock 1793-1864 Geologist, contributed to glacial geology, Professor of Geology at Amherst College, 'founded' the science of ichnology, state geologist for both Vermont & Massachusetts. William Whewell 1794-1866 General scientist, coined the terms 'anode', 'cathode', 'ion', 'scientist', 'physicist', & 'geological catastrophism', invented the anemometer, contributed to the study of tides.

Joseph Henry 1797-1878 Physicist, discovered the principle of self-induction, invented the galvanometer & the electromagnetic motor, professor at Princeton University, director of the Smithsonian Institute, charter member of the national Academy of Sciences, 'founder' and president of the American Association for the Advancement of Science, the Henry unit named after him. Sir Richard Owen 1804-1892 Zoologist, palaeontologist, comparative anatomist, coined the word 'dinosaur', discovered the parathyroid gland, first to described the giant Moas, discovered the trichinosis parasite. Matthew Maury 1806-1873 Hydrologist, oceanographer, 'founder' of the sciences of oceanography & hydrography, Professor of Meteorology at Virginia Military Institute, known as "the pathfinder of the seas". Louis Agassiz 1807-1873 Palaeontologist, ichthyologist, 'father' of glacial geology & glaciology, developed the concept of an Ice Age, coined the term 'Ice Age', established the museum of Comparative Zoology at Harvard, biology lecturer at Harvard.

Henry Rogers 1808-1866 Geologist, Professor of Natural History at Glasgow University, conducted a detailed study of the Appalachians & the coal fields of UK & USA. James Glaisher 1809-1903 Meteorologist, Superintendent at the Greenwich Observatory, developed the dew-point tables, established the British Meteorological Society, & the Aeronautical Society. Phillip H. Gosse Ornithologist, zoologist, Fellow of the Royal Society. Sir Henry Creswicke Rawlinson 1810-1895 Archaeologist, Assyriologist, exposed & deciphered the Behistun inscriptions of King Darius, British minister in Persia, member of the Council of India. Sir James Simpson 1811-1870 Physician, gynaecologist, 'founder' of gynaecology & anaesthesiology, discovered the medicinal use for chloroform, Professor of Obstetric Medicine at Edinburgh.

James Dana 1813-1895 Geologist, mineralogist, succeeded Benjamin Silliman at Yale, editor of the American Journal of Science, president of the Geological Society of America, president of the American Association for the Advancement of Science. Sir Joseph Henry Gilbert 1817-1901 Agricultural chemist, Fellow of the Royal Society, developed nitrogen & superphosphate fertilizers, helped found the first agricultural research station, Professor of Rural Economy at Oxford. James Joule 1818-1889 Physicist, established the mechanical theory of heat, discovered reversible thermodynamics, discovered the law of conservation of energy, first to estimate the speed of molecules of gas, co-discoverer of the Joule-Thompson Effect, chief 'founder' of thermodynamics, member of the Royal Society, president of the British Association for the Advancement of Science, the joule unit named after him. Thomas Anderson 1819-1874 Chemist, Regius Professor of Chemistry at Glasgow, Fellow of the Royal Society, discovered pyridine & other organic bases.

Charles Piazzi Smyth Sir George Stokes 1819-1903 Physicist, mathematician, developed Stoke's Law for viscosity, developed Stoke's Law for fluorescence, laid the foundation of fluid mechanics, Professor of Mathematics at Cambridge. Sir John William Dawson 1820-1899 Geologist, investigated & documented the geology of Canada, first president of the Royal Society of Canada, president of the American Association for the Advancement of Science. Gregor Mendel Botanist, discovered the genetic laws of inheritance, 'father' of genetics. Louis Pasteur 1822-1895 Physicist, chemist, bacteriologist, invented vaccination, pasteurization, sterilization & immunization, discovered the biological origin & control of fermentation, formulated the Law of Biogenesis, established the germ theory of disease, developed a vaccine for rabies, anthrax & diphtheria, 'father' of microbiology, Professor of Chemistry at Strasbourg, Director of Scientific Studies at École Normale (Paris), awarded the Legion of Honour, opposed spontaneous generation. Henri Fabre Entomologist, 'father' of modern entomology, opposed spontaneous generation.

Lord Kelvin (William Thomson) 1824-1907 Physicist, discovered Laws of Thermodynamics, invented the absolute temperature scale, supervised the design & laying of the trans-Atlantic cable, invented a tide predictor, ship's compass, & a depth-sounding gauge, Professor of Physics at Glasgow, Fellow of the Royal Society. Sir William Huggins Astronomer, discovered that stars are composed mostly of Hydrogen, identified the Doppler effect in astronomy. Bernhard Riemann 1826-1866 Mathematician, developed the concept of Non-Euclidean geometry, originated Riemannian geometry which was used by Einstein to develop his theory of General Relativity. Sir Joseph Lister (Lord Lister) 1827-1912 Physician, developed antiseptic surgery, invented dissolving stitches, fracture wiring, & surgical rubber drainage tubes, founded the Lister Institute of Preventative Medicine (London), Fellow of the Royal Society, Fellow of the Royal College of Surgeons, president of the British Association for the Advancement of Science, Professor of Surgery at Glasgow.

Balfour Stewart 1828-1887 Physicist, his study of Earth's magnetic field & upper atmospheric electric currents led to the discovery of the ionosphere. James Clerk Maxwell 1831-1879 Physicist, mathematician, developed the Electromagnetic Field Theory and the electromagnetic field equations, 'father' of statistical thermodynamics, calculated the speed of electromagnetic waves, member of the Royal Society, Professor of Experimental Physics at Cambridge. Peter Guthrie (P. G.)Tait 1831-1901 Physicist, mathematician, laid the foundation for vector analysis, Professor of Natural Philosophy at Edinburgh, Professor of Mathematics at Belfast, colleague of Lord Kelvin. John Bell Pettigrew Anatomist, physiologist, president of the Royal Medical Society. Lord Rayleigh (John Strutt) 1842-1919 Physicist, developed model analysis/dimensional analysis, discovered the Rayleigh scattering of light, developed the Raleigh-Jeans formula for black-body radiation, co-discovered argon and the inert gases, succeeded Maxwell at Cambridge, won the Nobel Prize for Physics.

Sir William Abney 1843-1930 Astronomer, studied interstellar molecules, president of the Royal Astronomical Society, president of the Royal Physical Society. Alexander MacAlister Zoologist, physiologist, Professor of Anatomy at Cambridge. Archibald. H. Sayce Archaeologist, Professor of Assyriology at Oxford, expert on Hittites and Assyrians. Sir John Ambrose Fleming 1849-1945 Physicist, electrical engineer, 'father' of electronics, invented the thermionic valve (the electron tube), devised the Fleming Rules for electric currents, Professor of Electronic Engineering at London, president of the Television Society, Fellow of the Royal Society. Edward H. Maunder Astronomer, solar astronomer, president of the British Astronomical Association. Sir William Mitchell Ramsay 1852-1916 Isotopic chemist, co-discovered argon, discovered krypton, xenon, radon & neon, discovered terrestrial helium, first to demonstrate the transmutation of elements through radioactive decay, won the Nobel Prize for Chemistry. Howard A. Kelly Physician, surgeon, Professor of Gynaecology & Obstetrics at John Hopkins University.

George Washington Carver Agricultural chemist, developed uses for crops. Wilbur Wright Sir Cecil P. G. Wakeley 1892-1979 Physician, Professor of Surgery at London, president of the Royal College of Surgeons. Dr Wernher von Braun Rocket engineer, planned space exploration & lunar landings, director of NASA References A. Lamont (1995), "21 Great Scientists Who Believed the Bible", Creation Science Foundation Ltd: Brisbane (Aust) H. Morris (1997), "Men of Science, Men of God" (13th printing), Master Books: Colorado Springs (USA) H. Morris (1984), "The Biblical Basis for Modern Science", Baker House Books: Grand Rapids (USA) H. Morris & G.E. Parker (1982), "What is Creation Science?", Master Books: Green Forest (USA) D.T. Gish (1993), "Creation Scientists Answer their Critics", Institute for Creation research: El Cajon (USA) F. De Angelis (1995), "The Origin of Life by Evolution: An Obstacle to the Development of Science", (Translated by L.

Pennington), Fernando De Angelis: Camucia (Italy) S.M. Huse (1983), "The Collapse of Evolution", Baker Book House Co: Grand Rapids (USA) Webster Publishing (1998), "World Encyclopedia 1998" (CD-ROM), Webster Publishing: Frenchs Forest (Aust) benzene - MOTM - HTML-only version Also available: JMol and VRML versions. History Michael Faraday was the first scientist to discover benzene in 1825. He extracted benzene from cylinders of compressed illuminating gas which had been collected from the pyrolysis of whale oil. Faraday called this newly discovered liquid bicarburet of hydrogen. Recognition of Faraday's enormous contribution to the sciences has been recognised in many ways, from his appearance on �20 notes to his depiction on stamps in various countries. In 1833, Eilhard Mitscherlich a German chemist produced what he called benzin via the distillation of benzoic acid (from gum benzoin ) and calcium oxide (lime).

Decarboxylation of benzoic acid to yield benzene In 1845 benzene was found in coal tar by the English chemist Charles Mansfield, working under August W. Hofmann . Four years later, Mansfield began the first industrial-scale production of benzene, based on the coal-tar method. Coal tar is made by destructively distilling coal and is still a source of benzene today. Benzene was first synthesized in a laboratory in 1870 by Pierre Berthelot who passed acetylene through a red hot tube. Physical Properties Benzene is a non-polar colourless, inflammable liquid, with a sweet and distinctive aromatic smell that some find pleasant. But beware as benzene is highly toxic and absorbed through the skin. Benzene has a melting point of 5.5°C and a boiling point of 80°C and is therefore a liquid at room temperature. Benzene is immiscible with water and will form the upper layer since it has a lower density of 0.879 g/cm3. Benzene is a very good solvent for organic compounds, but it is safer to use its derivative methylbenzene (toluene).

Structure For a quarter of a century following its discovery, benzene's structure continued to puzzle the world's greatest scientists. It was known to have a molecular weight of 78 which was due to the presence of six carbon atoms (6 x 12) plus six hydrogen atoms (6 x 1). August Kekule was one of the organic chemists who was working on the structural elucidation of benzene. He originally placed all six carbon atoms in a row but soon realised that this did not make sense for where was he to put all the hydrogen atoms? The story goes that whilst trying to solve the problem of benzene's Kekule had a daydream whilst dozing on a London bus. The old saying goes that: "you wait ages for one bus, then three come along at once". In Kekule's case, six came along. Kekule visualized a snake with its tail in its mouth that was spinning around. That snake was benzene, biting itself in the tail, which made sense if it possessed alternating single and double bonds. Kekule's dream is shown as an interesting animation .

Kekule's dream of a snake eating its own tail, is an ancient symbol called the Ouroboros which represents the cyclicality of life. One should bear in mind that this 'story' first appeared in the journal Berichte der Durstigen Chemischen Gesellschaft, which is a parody of the respected journal Berichte der Deutschen Chemischen Gesellschaft. What is clear is that Kekule's understanding of the tetravalent nature of carbon was built on the foundation of the often overlooked work of Archibald Scott Couper . Every student who has ever drawn covalent bonds as lines on paper joining atoms is following in Couper's footsteps. The former East Germany (DDR) commemorated the work of Kekule on a stamp which shows his structure of benzene. Kekule drew what he believed to be two identical structures for benzene and now he needed to find proof that his 'daydream' was correct. Rod Beavon of Westminster School has written an online biography of Kekule . Kekule structures for benzene It is important to realise that benzene has a planar structure.

The distance between adjacent carbon atoms found by X-ray diffraction is 0.139 nm (139 picometres). This is a distance which is intermediate between the longer single C-C bonds (147 pm) and the shorter double C=C bonds (135 pm). The relative length of the C-C bonds in benzene can be explained in terms of the delocalized electrons, which leads to the intermediate bond lengths. The cyclic nature of benzene was finally confirmed by the eminent crystallographer Kathleen Lonsdale . Molymod of benzene. A t-shirt showing the importance of dreams is available by clicking here . In 1931 Linus Pauling proposed his resonance theory which describes delocalised electrons and is able to account for benzene's known reactions. This theory explained the stability of the delocalised electrons (lower energy) and the reason why benzene's reactions are mainly electrophilic substitution reactions. Pauling's theory states that instead of the kekule structures I and II shown below we have a single structure III with the delocalised electrons shown on paper as a circle in the middle of a hexagon.

Problems with Kekule's structure were first hinted at when it became apparent that the enthalpy of hydrogenation of benzene (-208 kJ mol-1) was found not to be three times the value found for cyclohexene (-121 kJ mol-1) with its one C=C bond. The 'missing' energy of hydrogenation (155 kJ mol-1), is called resonance energy, and is a measure of benzene's stability. The aromatic stability comes from the sideways overlap of electrons in the π-bond above and below the six carbon atoms in the ring. The delocalised electrons are shown as a circle in the hexagon. The reason substitution is preferred is that benzene and its derivatives are more thermodynamically stable after a substitution reaction than if an addition reaction took place. For those who realise the bond order in benzene is in fact 1.5 then another way to represent the structure of benzene IV is as a hexagon with a dotted circle inside of the hexagon. Like the spelling of sulfur, the drawing of benzene can also lead to debate amongst chemists.

Others molecules having C6H6 An interesting challenge to give our brightest students is to get them to work out the structure of three other molecules having the same molecular formula as benzene. Once these isomeric structures are solved they could also be asked to predict their spectra. There are two linear structures which are the positional isomers; 1,5-hexadiyne and 2,4-hexadiyne, and a cyclic structure 5-methylene-1,3-cyclopentadiene, known trivially as fulvene . Spectra Benzene's spectra are surprisingly simple unless one considers its planar structure and its symmetry. The proton nmr spectrum of benzene consists of a single peak at 7.26 ppm as all its protons are equivalent. The signal is downfield (+δ) compared to the two equivalent vinylic protons (=CH) of cyclohexene at 5.6 ppm due to the diamagnetic ring current . Benzene's peak is shifted downfield because of a ring current effect where the circulating delocalized electrons are at 90° to the applied magnetic field.

The result is that benzene's protons are deshielded because the induced magnetic field is in the same direction as the applied magnetic field. This means that a higher frequency is needed to achieve resonance because the local magnetic field is higher for the protons. The diagram below should help for those not studying Physics at advanced level as should a look at Ampere's Law . Likewise the carbon-13 nmr spectra of benzene is a single peak at 128 ppm. The mass spectrum of benzene is worth a look at, if only because the [M+1]+ peak is 6.6% of the [M]+ peak due to the presence of the 13C isotope. The infra-red (IR) spectrum of benzene is one of the most simple and it shows all the expected aromatic C-H resonances . C-H stretches typically occur around 3000 cm-1 as sharp troughs and also =C-H bending around 1500 cm-1. Crystal structure The crystal structure of benzene was first published in 1932 by two scientists from Leeds University and the original paper can be found in Cox & Smith , Proc. Roy.

Soc., A, 135, 491 (1932). You too can look at the crystal structure of benzene by clicking on a wonderful resource written by Chas McCaw (Winchester College) on crystal structures. Test for arenes There is no specific positive test for arenes. They do not decolourize bromine water since they do not readily undergo addition reactions. Aromatic compounds do however burn with smoky flames due to the very high percentage of carbon in these molecules. Reactions of benzene Benzene is an important feedstock for the chemical and pharmaceutical industries. It is for this reason that its reactions are studied in detail in sixth forms. The chemistry of aromatic compounds is dominated by electrophilic substitution reactions. In these reactions the π-cloud and delocalisation is preserved. With Nitric acid Concentrated nitric acid reacts slowly and inefficiently with benzene, producing a yield of around 5% nitrobenzene; a toxic yellow oil with a melting point of 5°C and a boiling point of 210°C. When a nitrating mixture of concentrated sulfuric and concentrated nitric acid is used much higher yields are produced.

This is because the sulfuric acid catalyses the formation of the electrophilic 'nitronium ion' (NO2+) according to the following equation: HNO3 + 2 H2SO4 NO2+ + 2 HSO4- + H3O+ The 'nitronium ion' then goes on to react with the benzene in a electrophilic substitution reaction producing predominantly nitrobenzene. If the temperature is allowed to rise above 50°C then some dinitrated product is produced which is a pale-yellow solid at room temperature. With RX (Friedel-Crafts alkylation) Friedel-Crafts alkylation is also an electrophilic substitution reaction in which a alkyl group replaces a hydrogen atom on a benzene ring. The Friedel-Crafts alkylation requires the use of a catalyst to form the electrophile from the alkyl halide and anhydrous aluminium chloride is normally used for this purpose.

The electrophile (R+) is formed according to the following equation: RX + AlCl3 R+ + AlCl4- An example of a Friedel-Crafts alkylation is shown right: With RCOX (Friedel-Crafts acylation) Friedel-Crafts acylation is very similar to a Friedel-Crafts alkylation, it is the electrophilic substitution reaction of an acyl halide with benzene. An acyl group is an alkyl group attached directly to a carbonyl group. Once again the electrophile (CH3CO+) is generated using AlCl3 as the catalyst. CH3COCl + AlCl3 CH3CO+ + AlCl4- In this example, ethanoyl chloride is reacted with producing the phenylethanone known trivially as acetophenone) according to the reaction shown on the right. With halogens (Friedel-Crafts halogenation) Benzene reacts with halogens in the presence of a catalyst (halogen carrier) producing halobenzenes (C6H5X) and hydrogen chloride in a substitution reaction. The catalyst normally used is aluminium or iron powder.

These metals react with some of the halogen, for example chlorine, forming the corresponding trihalide salts of the metal according to: 2 Al + 3Cl2 2AlCl3 The overall reaction is: An interesting side reaction is that in the presence of UV light and high temperatures, benzene can undergo an addition reaction forming an unsaturated compound, for example with excess chlorine the compound 1,2,3,4,5,6-hexachlorocyclohexane is formed according to: Sulfonation Aromatic sulfonation is when an H is replaced by SO3H (a sulfonic acid group). In the case of benzene, it needs to be heated with conc. H2SO4 for 8 h to produce benzenesulfonic acid. This reaction is too slow and not to be attempted as benzene is implicated in childhood leukemia. Instead, it's better (faster and safer) to use toluene (methylbenzene), as the methyl (CH3) group is electron-releasing and speeds up the reaction. The procedure is: Add 30 drops of conc. H2SO4 to 12 drops of (toluene) in a test-tube.

Warm until the methylbenzene has dissolved into the acid layer. Pour the mixture into 30 cm3 of a cold saturated solution of sodium chloride. White crystals of sodium methylbenzene sulfonates are formed. A summary of Aromatic Reactions A selection of downloadable aromatic reactions is to be found in Chapter 22 of the Pre-U chemistry course book that I finished in 2010. Have fun working out the names of compounds A-M and the conditions and mechanisms needed for the reaction steps 1-12. Other arenes The term 'aromatic' was originally used for naturally occurring, sweet-smelling compounds with an aroma. Today the term is associated with benzene rings. A selection from the multitude of aromatic compounds include; naphthalene, anthracene and pyrene. Can you think of another way to fuse three aromatic rings that is different to anthracene? Remember, Einstein said, "imagination is more important than knowledge". Click here when you think you have the answer.

Inventor Michael Faraday Michael Faraday Father of Electronics by Charles Ludwig / Paperback (May 1988) / Herald Pr Ludwig retells Michael Faraday's remarkable life story in fictionalized form, presenting the man who invented the electric motor, the dynamo, the transformer, and the generator. by Michael Faraday, Peter Day (Compiler) / Paperback - 212 pages / Inst of Physics Pub (1999) An attractive collection that serves well as an introduction to this extraordinary man. Michael Faraday by Geoffrey Cantor, David Gooding / Paperback (October 1996) / Humanity Books This biography follows his early life and career, his role in the Royal Institution and in civic and military science, and his influence on science and engineering. by Michael Faraday / Paperback - 88 pages (May 1993) / Prometheus Books Certainly a true classic. This book will appeal to both the layman and the technically inclined. by James Clerk Maxwell / Paperback 3rd edition (January 1991) / Dover Pubns This volume covers magnetism and electromagnetism.

ON THE WEB: A complete edition of Faraday's approximately 4800 extant letters is being published under the editorship of Frank James at the Royal Institution. Brief overviews of each volume are given. (URL: His discoveries have had an incalculable effect on subsequent scientific and technical development. He was a true pioneer of scientific discovery. Presented by the Institution of Electrical Engineers. (URL: Earth begins to emit a noticeable glow! During the early 19th century, newspaper headlines across Europe cried out " Napoleon escapes from St. Elba... Continental armies on the march!! During the same period, these newspapers barely noted Michael Faraday's discovery of the kinetic flashlight. Fifty years later, Napoleon was gone, however due to Faraday's discovery, for the first time in it's five billion year history, the night side of the earth began to emit a noticeable glow! (URL: ANOTHER OPINION "I discovered the principle of electromagnetic induction, not Michael Faraday." Joseph Henry (1797-1878) is widely considered the foremost American scientist of the 19th century.

Although Henry at an early age appeared to be headed for a career in the theater, a chance encounter with a book of lectures on scientific topics turned his interest to science. Henrys early investigations concerned electromagnetic phenomena, and his discovery of electromagnetic self-induction in 1831 established his reputation in America. Interestingly, Henry appears to have discovered the principle of electromagnetic induction independently of British scientist Michael Faraday, but because Faraday published his results before Henry, he is credited with the discovery. In 1846 Henry was named first Secretary of the newly-established Smithsonian Institution, a position he held until his death. In 1868 he was elected President of the Academy; this position, too, he held until his death. This according to the National Academy of Sciences, an advisor board to the government in scientific matters. (URL: Electronic Text version of "Faraday as A Discoverer (Page removed from site.) By JOHN TYNDALL From the Fifth Edition, published Longmans, Green, and Co.

London 1894 ( Gutenberg E-text Project) (URL: ftp://uiarchive.cso.uiuc.edu/pub/etext/gutenberg/etext98/fdayd10.txt) DID YOU KNOW?: To honor his accomplishments, a unit of electricity was named after Michael Faraday. The "farad" measures capacitance, an amount of electrical charge. Reference Sources in BOLD Type This page revised History & Future - Biting one's own tail: the history of benzene Biting one's own tail: the history of benzene Benzene is one of chemistry's great stars. It has numerous applications, and is the basis for manufacturing many more useful compounds. But did you know its structure was a subject of a lot of controversy in the 19th century? The discovery of benzene Benzene was first discovered by Michael Faraday in 1825, who called it bicarburet of hydrogen. In 1833, it was discovered again by Eilhard Mitscherlich who distilled it from gum benzoin (that's how it gets its name). Since it dissolves many organic and greasy substances, Benzene found widespread use in removing paint and organic stains from metal surfaces.

In 1849, Charles Mansfield perfected a method for extracting benzene from coal tar on industrial scales. Confusion about its structure As an important chemical, many efforts were made to understand its chemical structure. It was known that benzene had six atoms each of carbon and hydrogen (C6H6). This puzzled chemists, because each carbon atom can form bonds with four other atoms. This had been proved by Friedrich August Kekule', the leading chemist of those times. In benzene, the carbon atoms were binding just two other atoms. It seemed to not obey the rule set by Kekule. Archibald Scott Couper and Joseph Loschmidt suggested possible structures in terms of 'unsaturated' carbon atoms. In a molecule, a carbon atom is said to be 'saturated' if it is linked to four other atoms. It is 'unsaturated' if it links to another carbon atom with more than one bond. Saturated Unsaturated

Question: Which British scientist discovered benzene?
Answer: MICHAEL FARADAY