bluuebunny/crossref_metadata_2025 huggingface dataset:
The ideas of statistical mechanics
Authors: Bowley Roger , Sánchez Mariana
Published: September 2023

This chapter discusses the microscopic basis of entropy, how to calculate the equation of state for a system, and the physical basis of the second law that ensures that entropy increases as a function of time. It cites Ludwig Boltzmann's hypothesis, which states that the entropy of a system is related to the probability of its state and its basis is statistical. The chapter also focuses on statistical mechanics, wherein thermal properties are calculated by using statistical ideas together with a knowledge of the laws of mechanics obeyed by the particles that make up a system. The chapter highlights that the power of statistical mechanics is grounded in the fact that it uses simple ideas and involves general techniques. It demonstrates the notion of statistical probability, which is obtained by considering a series of identical measurements made over a period of time on a single system.
Planck's distribution
Authors: Bowley Roger , Sánchez Mariana
Published: September 2023

This chapter considers the distribution of the energy U among N oscillators of frequency ν, noting that an infinite number of distributions are possible if U is viewed as a divisible without limit. It discusses the theory of black-body radiation, which was developed by Max Planck in 1900 and gave birth to quantum physics. It defines a black body as one that absorbs all the radiation incident upon it. No radiation is reflected so that it looks black when it is cold. The chapter explains that objects emit electromagnetic radiation at a rate which varies in relation to their temperature. This radiation cannot be seen because its wavelength is the wrong frequency for the human eye. The chapter states that a body in thermal equilibrium with its surroundings emits and absorbs radiation at exactly the same rate.
Continuous phase transitions
Authors: Bowley Roger , Sánchez Mariana
Published: September 2023

This chapter explores the occurrence of a continuous phase transition when the minimum in the thermodynamic potential evolves smoothly into two or more equal minima. It refers to an example of the liquid–gas phase transition held at constant pressure wherein the system is on the liquid–gas coexistence line and the thermodynamic potential is the generalized Gibbs free energy. It also analyses the temperatures above the critical temperature wherein there is no evidence of two phases and the system has a uniform density which results in a single phase called the fluid phase. The chapter points out that bubbles of gas and drops of liquid in the system are intermingled on all length-scales from the macroscopic to the atomic. It elaborates that the bubbles represent fluctuations of the system away from the average density.
Electrochemical principles
Authors: Brett Christopher M. A. , Brett Ana Maria Oliveira
Published: September 2023

This chapter discusses electrochemical principles. Electrochemistry is the study of phenomena caused by charge separation. In the context of electrode processes, which are heterogeneous in nature, it deals with the study of charge transfer processes at the electrode/solution interface, either in equilibrium at the interface, or under partial or total kinetic control. Most of the charge transfer processes are transfer of electrons, which can be represented in the simplest case of oxidised species and reduced species, both soluble in solution. In a real situation, both reduction and oxidation must occur to an equal extent, so as not to violate the law of conservation of energy. The chapter then looks at electrochemical cells, the kinetics of electrode reactions, the interfacial region and electrolyte double layer, hydrodynamic electrodes, microelectrodes, and electroanalytical titrations.
Voltammetric sensors
Authors: Brett Christopher M. A. , Brett Ana Maria Oliveira
Published: September 2023

This chapter examines voltammetric sensors, which function by the measurement of the current response as a function of applied potential (or the potential response as a function of applied current). In other words, they depend on the registering of current–potential profiles. A special case of voltammetric sensors is amperometric sensors, where a fixed potential is applied and the current is registered. The recording of current as a function of time (chronoamperometry) can give important and useful information, as can the charge passed, which is measured using coulometry and as a function of time in chronocoulometry. The chapter then focuses on describing the basic principles of a number of different types of non-steady-state techniques and their use in analysing electroactive species in solution, together with more elaborate schemes for application to detection of trace species.
Introduction
Authors: Cox P. A.
Published: September 2023

This chapter provides a background on the study of solids and the factors that determine their structures and properties, which forms an important part of chemistry. It refers to the electronic theory of valency. This theory provides the basis for a modern understanding of chemistry and represents an important reason for studying the electronic structure of solids. The chapter also describes the characteristic properties of solids that depend directly on the behaviour of electrons. The chapter highlights the applications of solids that depend on electronic properties and form the basis for integrated circuits, lasers, magnetic recording tapes, and solar energy converters. It introduces the basic principles involved in studying and understanding the electronic structure.
The effects of electron repulsion
Authors: Cox P. A.
Published: September 2023

This chapter talks about electrostatic repulsion between electrons in the orbital pictures of atoms and molecules, which is treated in an approximate way. It reviews how the molecular orbital theory can break down if the interaction between atomic orbitals is weak, such as in the dissociation of a molecule. It also analyses compounds of transition elements and lanthanides wherein band theory does not work, and the electrons are localized by their mutual repulsion. The chapter details how electrons become localized and how this affects their electronic properties. It highlights the Hubbard model, which is considered the most fruitful approach to electron repulsion in solids and occurs between two electrons on the same atom.
Introduction
Authors: Donohoe Timothy J.
Published: September 2023

This introductory chapter provides an overview of the processes of oxidation and reduction. Oxidation and reduction together are themes that run through the very core of organic chemistry. Oxidation of an organic substrate may be defined as the addition of oxygen, the removal of hydrogen, or the removal of electrons from that compound. Similarly, reduction can be defined as the removal of oxygen, the addition of hydrogen, or the addition of electrons to an organic substrate. The classification of organic compounds into oxidation states is difficult and inconsistencies abound; and although we can devise a system for achieving this classification, it is not particularly useful to organic chemists. Instead, organic chemists find it convenient to place functional groups into five different categories (or levels) depending upon the level of oxidation contained within.
Metallated alkenes
Authors: Jenkins Paul R.
Published: September 2023

This chapter talks about direct and indirect methods that can be used for the preparation of metalated alkenes, including the alkenyl potassium reagent produced using the base potassium amide in liquid ammonia. It examines the equation that shows that allylic deprotonation is a competing reaction that becomes more important as the ring size increases. It also points out how sodium and potassium alkenes are not used in synthesis to anything like the same extent as the corresponding lithium compounds. The chapter describes reactions that are referred to as the lithium-halogen exchange, which is considered as a nucleophilic attack on the halogen atom that occurs with retention of the olefin configuration. The chapter explains that the alternative reaction is the conversion of tin compounds to lithium counterparts wherein the retention of the olefin configuration is observed.
Metallated alkynes
Authors: Jenkins Paul R.
Published: September 2023

This chapter talks about the high-s character of an sp hybridized carbon atom, which meant that an acetylene anion is stabilized, and the deprotonation of acetylenes, which is possible with a wide range of strong bases. It emphasizes the careful control of conditions of a strong base in the deprotonation of an acetylene to avoid side reactions, particularly on substituted acetylenes. It also describes the formation of danions as a major side reaction that occurs if the acetylene is momentarily exposed to an excess of base, the appropriate solvent is used, or the reaction temperature rises. The chapter explains the elimination of hydrogen halide with an amide base in liquid ammonia, which is a useful alternative to deprotonation as a synthesis of metalated alkynes. It clarifies how alkylation occurs with primary alkyl bromides and iodides under basic conditions involving liquid ammonia as solvent.
Metallated heterocyclic compounds
Authors: Jenkins Paul R.
Published: September 2023

This chapter focuses on a small selection of heterocyclic compounds providing an estimate of how any heterocyclic ring can be metalated. It considers the metallation of the heterocycles furan, thiophen, and N-methylindole, which are deprotonated by butyllithium on a carbon α to the heteroatom. It also explains the inductive effect of the heteroatom as it stabilizes the carbanion by withdrawing electron density from it, noting that this heteroatom effect is one of the main ideas in explaining aromatic lithiation. The chapter discusses 2-lithiothiophen and 2-lithiofuran, which are considered the most well-behaved of all the lithium anions and react well with alkyl halides without giving elimination as a side reaction. It reviews the alkylation of 2-lithiothiophen and 2-lithiofuran that occurs between 0 and 50°C.
Mechanism and theory
Authors: Harwood Laurence M.
Published: September 2023

This chapter provides a background on the various categories of rearrangement mechanism and determines which categories involve polar intermediaries. It discusses initial fragmentation, which gives rise to a positively or negatively charged species that can undergo rearrangement. It also emphasizes how nucleophilic rearrangements are encountered far more commonly than electrophilic rearrangements. The chapter explains homolytic rearrangements as reactions that have initial bond cleavage and produce a radical species that possess an unpaired electron prior to migration, while pericyclic rearrangements pass through highly ordered transition states. It cites the Claisen and Cope rearrangements as examples of molecular arrangements and are termed 3,3-sigmatropic rearrangements.
Rearrangements to electron deficient nitrogen and oxygen
Authors: Harwood Laurence M.
Published: September 2023

This chapter discusses important classes of rearrangement in which the migration terminus is either an electron deficient nitrogen or an oxygen atom. It examines the migration of nucleophilic rearrangements to nitrogen that occur concurrently with the displacement of a substituent from the nitrogen or by a stepwise process involving initial fragmentation to form a nitrene at the terminus. It also talks about the departure of a leaving group from the nitrogen that initiates rearrangement and migration of a control group. The chapter considers rearrangements that follow concerted mechanisms with migration, which occur at the same time as the loss of the leaving group from nitrogen. It points out that the departure of a leaving group from nitrogen initiates arrangement and control on which group migrates.
Acid catalysed aromatic rearrangements
Authors: Harwood Laurence M.
Published: September 2023

This chapter reviews arbitrary distinction to create the classification of aromatic rearrangements. It considers reactions that are initiated by the generation of an arenium ion and involve migration around the aromatic ring or from a side chain onto the aromatic nucleus. It also points out that the migration terminus positioned on an aromantic ring is initiated by protonation or by a Lewis acid, which is commonly a consequence of equilibration to form thermodynamically stable products. The chapter highlights intramolecular migration, which occurs via a π-complex that leads to equilibration between arenium ion species. It talks about the mechanism of arenium ion generation which bears a close resemblance to the mechanism for electrophilic aromatic substitution.
Carbenes
Authors: Moody Christopher J. , Whitham Gordon H.
Published: September 2023

This chapter talks about neutral, divalent, and highly reactive carbon carbenes. These are considered as intermediates and are generally written as R2C. It describes methylene as the simplest carbene, which many early chemists believed was a stable entity and have attempted various experiments for its generation. It also explains the term carbene. This term is universally used for divalent carbon species named as substituted derivatives of carbene, such as phenylcarbene (PhCh) and dichlorocarbene (Cl2C). The chapter examines the bonding electrons and non-bonding electrons associated with carbenes. It looks at the possibility of two electronic arrangements or spin states, such as the singlet carbene that has the spins of its non-bonding electrons paired.
Introduction
Authors: Mann John
Published: September 2023

This chapter focuses on the two major classes of natural products: primary and secondary metabolites. Secondary metabolites are compounds that are unique to a particular species or of relatively limited occurrence that comes from two species of poppy. The chapter also points out that secondary metabolites have no proven effect on the organism producing them, although they may have a deterrent effect on would-be predators or competitors. The chapter discusses how organisms evolve through changes in their genetic make-up and how mutations may result from exposure of the organism to ionizing radiation, UV irradiation, certain chemicals, or viruses. It mentions genetic changes that result in alterations to primary metabolic pathways that are usually detrimental, and the organism may die.
Fatty acids and derivatives
Authors: Mann John
Published: September 2023

This chapter deals with glycerides. These provide an energy store as they can be broken down to acetate and used for biosynthesis or fed into the citric acid cycle for the construction of other small building blocks. The chapter discusses the oleic acid that is produced by many species of Compositae. This has an anti-microbial function, while the arachidonic acid is produced by the broad bean in response to stress and has an antifungal function. The chapter also describes arachidonic acid as the biosynthetic precursor of a large family of metabolites known as eicosanoids. The chapter mentions the biosynthesis of fatty acids. These are under the control of enzymes called fatty acid synthases. It analyszes bacterial synthases that compromise aggregates of six or seven discrete enzymes.
Polyketides
Authors: Mann John
Published: September 2023

This chapter discusses the condensation of acetyl-SCoA with malonyl-SCoA units that gives rise to numerous aromatic compounds, many of which have meta-disposition of hydroxyl groups. It mentions products of the polyketide pathway and its typical examples, such as 6-methylsalicyclicacid, antifungal compound griseofulvin, mycotoxins patulin, and ochratoxin. It also refers to products of moulds and other soil and airborne microorganisms. These are abundant in bacteria of the family actinomycetes. The chapter examines biomimetric synthesis. This uses a triketide that lead to the formuilation of a polyketide hypothesis, which envisaged the biosynthesis of polyphenols from polyketomethylene in intermediates. The chapter assesses structures of polyketide. We owe their diversity to carbonyl groups that may or may not be reduced during biosynthesis.
Terpenoids and steroids—the isoprenoids
Authors: Mann John
Published: September 2023

This chapter analyszes acetyl-SCoenzyme A, which is the main building block of the terpenoids and steroids. These contain diverse structures, such as α-pinene. The chapter recounts the establishment in the nineteenth century of the structures of the simple ten-carbon compounds or monoterpenes which contain an integral number of five-carbon units. It also mentions the pyrolysation of monoterpenes. This gives rise to isoprene as a major decomposition product. The chapter notes the importance of the biogenic speculation of isoprene as a building block in structural studies. The chapter considers HMG-CoA reductase as the most important enzyme as it catalyses the rate-determining step for the whole route to cholesterol. It explains how the inhibition of HMG-CoA reductase provides a viable strategy for lowering levels of cholesterol in the blood.
Ecological chemistry
Authors: Mann John
Published: September 2023

This chapter reviews the use of secondary metabolites as mediators of interactions between organisms and the identification of inter- and intra-species interactions known as ecological chemistry. It assesses speculation on the origins of the main secondary metabolic pathways wherein secondary metabolites that are produced by plants and insects arose in response to the continually changing interactions that occur between species. It also discusses how plants and insects have been co-evolving for millions of years. This resulted in plants developing biosynthetic pathways that produce toxic or distasteful compounds. The chapter mentions how insects have devised means of overcoming the defences of plants, even using their deterrent chemicals for their own purposes. It notes subtle changes in the levels of particular enzymes. These alter the structure or quantity of a secondary metabolite and lead to an improvement in the survival prospects of the producer species.
The structure and spectrum of the hydrogen atom
Authors: Softley T. P.
Published: September 2023

This chapter considers the structure and spectrum of the hydrogen atom. The fraction of hydrogen in atomic form in a room temperature sample is negligibly small under normal conditions. The emission spectrum of atomic hydrogen is therefore normally recorded by setting up an electric discharge in a low-pressure hydrogen lamp. In this light, the chapter illustrates practical emission spectroscopy, before turning to the Schrödinger equation for the hydrogen atom. It then discusses the wavefunctions and quantum numbers, before providing a solution of the Schrödinger equation. As the appearance of any atomic spectrum is determined not only by the underlying energy levels, the chapter delves into population factors and selection rules, including a quantum mechanical formulation of the latter. To conclude, the chapter discusses spin–orbit coupling and provides an application in chemical reaction dynamics.
The spectra of the alkali metals
Authors: Softley T. P.
Published: September 2023

This chapter focuses on alkali metals. It first explores studies of the alkali metal absorption spectra before turning to the energy levels of many-electron atoms. The energy levels of such atoms will inevitably have a more complicated structure compared to hydrogen, because the quantized energies are now determined not only by the electron–nucleus attraction, but also by the mutual repulsion between electrons. With this in mind, the chapter next turns to electron configuration—in short, the description of which orbitals are occupied by the electrons in the atom—as well as the related Pauli exclusion principle. The spectra of many-electron atoms, penetration and shielding, the spectra of the alkali metals, and the quantum defect are also explored. The chapter also discusses transition energies and the determination of ionization energies. Finally, it takes a look at the laser cooling of sodium atoms.
The spectrum of the helium atom
Authors: Softley T. P.
Published: September 2023

This chapter discusses the spectrum of the helium atom. For the helium atom, there is now more than one source of angular momentum, with both electrons having spin angular momentum and possibly both having orbital angular momentum. The coupling of these angular momenta has important effects on the energy levels. The degeneracies of the various configurations are generally higher than for the one-electron case. However, as this chapter shows, electron-electron interactions lead to a lifting of these degeneracies, and hence to a complication of the energy level structure compared to hydrogen or the alkali metals. The chapter goes further in depth by looking at total spin angular momentum and the spectrum of helium. The spin–orbit coupling, spin wavefunctions and the Pauli principle, the Fermi hole, the exchange and coulomb integrals, the configuration interaction and double excitations, and finally the population inversion in the He–Ne laser are discussed.
Voltammetry: the study of electrolysis mechanisms
Authors: Fisher A. C.
Published: September 2023

This chapter clarifies the measurement of electrode currents as a function of the voltage applied to the electrolysis cell, which provides detailed information about the mechanism of the cell reaction of interest. It reviews the simplest approach to the measurement of current/voltage characteristics that involves two electrodes: a working electrode and a reference electrode. The working electrode is where the reaction of interest occurs, while the reference electrode provides a stable and fixed potential when a voltage is applied. The chapter examines the simple two-electrode arrangement that is used to measure current/voltage curves, wherein only a tiny current is passed. It also refers to voltametric experiments that use a three-electrode system in which an auxiliary or counter electrode is used.
Synthetic aspects 2. The complexes
Authors: Constable Edwin C.
Published: September 2023

This chapter begins by evaluating non-template synthesis of complexes. The simplest method of preparing a metal complex is to treat the ligand of choice with a derivative of the metal of choice in an appropriate solvent. This is the traditional method of coordination chemistry and is highly effective when the rate of complexation of the ligand is reasonably fast and when the ligand itself is stable under reaction conditions. In practice, this approach is used for the synthesis of the majority of complexes of crown ethers, aza and thia macrocycles, many mixed donor ligands, and ligands such as porphyrin and phthalocyanine. The chapter then looks at the template effect, including the kinetic template effect and thermodynamic template effect, before considering hole-size effects. It also discusseds catenanes.
Other aspects of macrocyclic chemistry
Authors: Constable Edwin C.
Published: September 2023

This chapter addresses some other aspects of macrocyclic chemistry not covered in earlier chapters and begins by looking at the binding of organic cations. To date, it has been assumed that coordination chemistry is limited to inorganic cations. However, the interaction of Group 1 metal ions with crown ethers and cryptands has a significant electrostatic component, which suggests that organic cations such as ammonium ions might also be bound by macrocyclic ligands. The chapter then considers the binding of anions. In contrast to the binding of organic cations, where the ligand acted as the hydrogen bond acceptor and the guest as the hydrogen bond donor, the situation is usually reversed in anion binding. Finally, the chapter studies biocatalysis by macrocyclic complexes.
Modern Liquid Phase Kinetics
Authors: B.G. Cox
Published: September 2023

Modern Liquid Phase Kinetics aims to show that the world is not at equilibrium, and the events that give vitality and movement are transitions towards equilibrium from the present state of imbalance. Chemical transformations often contribute fundamentally to this process and their study is challenging and important. The early chapters of this text provide a basic introduction to the kinetics of simple and complex reaction systems in solution. The remaining chapters present a treatment of the more advanced topics, comprising solvent effects, fast reaction techniques, and heterogeneous liquid—liquid two-phase systems. The last introduces currently active and important research areas in solution kinetics, including phase-transfer catalysis, and diffusion and transport in chemical and biological membranes.
Empirical treatment of reaction rates
Authors: B.G. Cox
Published: September 2023

The chapter discusses the starting point for most kinetic investigations of chemical reactions, which is the determination of the rate of the reaction and its dependence upon the concentrations of the species involved. It clarifies that a closed system is typical for a liquid phase reaction in a flask or a closed reactor. It also points out that liquid phase reactions are effectively constant-volume processes which change when reagents are added. The chapter reviews isothermal conditions. These are convenient to work with and allow the use of temperatures as an independent variable in controlling the reaction rate. It distinguishes homogeneous reactions, which require the presence of at least two-phases to proceed, with heterogeneous reactions, which are irrespective of where the reaction is occurring of the distribution of the reagents among the phases.
The Mechanisms of Reactions at Transition Metal Sites
Authors: Henderson Richard A.
Published: September 2023

The Mechanisms of Reactions at Transition Metal Sites provides an introduction to this topic. Understanding the mechanisms of the reactions at transition metal sites is a key component in designing synthetic methods, developing industrial homogeneous catalysts, and investigating metalloenzymes. The chapters here provide a broad-based and systematic guide through the fundamentals of transition-metal mechanistic chemistry. Chapters in this book cover substitution reactions, electron transfer reactions, and ligand-based reactions.
Introduction to inorganic reaction mechanisms
Authors: Henderson Richard A.
Published: September 2023

This chapter reviews the current knowledge of inorganic reaction mechanisms spread across all areas of the periodic table, covering a wide range of reaction types, geometries, and coligands. It suggests that the principles of mechanistic chemistry present a unifying description of the multitude of reactions that constitute transition metal chemistry. It explains that mechanistic chemistry is preoccupied with the nature of intermediates, which may attain high enough concentrations for them to be detected spectroscopically and be so long-lived as to be isolable. The chapter emphasizes the importance of the prerequisite that the structure of the reactants and products must be known. It looks at fundamental reactions in transition metal chemistry.
Electron transfer mechanisms
Authors: Henderson Richard A.
Published: September 2023

This chapter describes electron transfer reactions as a dominant feature of transition metal chemistry which is of fundamental importance in defining its characteristics in the periodic table. It analyses the mechanisms of electron transfer between two metal complexes and two distinct types of mechanisms: the inner sphere and outer sphere pathways. It also explains how the distinction between the two mechanisms resides in whether the reactants share a ligand during the act of electron transfer or not. The chapter discusses the importance of substitution processes as a component of the overall reaction in the inner sphere electron transfer mechanisms. It explores the mechanisms of electron transfer by relating the inner sphere pathway to the mechanism of the outer sphere pathway.
Metal carbonyl complexes
Authors: Bochmann Manfred
Published: September 2023

This chapter discusses metal carbonyl complexes, one of the most important classes of organometallic compounds. Carbon monoxide (CO) binds firmly to blood haemoglobin and renders it unavailable for oxygen transport. Metal carbonyls, in particular the volatile compounds, are therefore highly toxic; nickel tetracarbonyl Ni(CO)4 is a very potent carcinogen. The structures of metal carbonyls can be explained using the 18-electron rule. This is fulfilled if Cr, Fe, and Ni bind six, five, and four CO ligands, respectively, to give monomeric compounds. The carbonyls of Mn and Co form metal–metal bonded dimers to attain an 18 VE configuration. The chapter then looks at metal carbonyl anions, metal carbonyl hydrides, metal carbonyl halides, and metal carbonyl clusters.
Metal alkyl complexes
Authors: Bochmann Manfred
Published: September 2023

This chapter examines metal alkyl complexes. The making and breaking of metal–carbon σ-bonds plays an important role in organometallic chemistry and is central to its application to catalysis. Whenever alkanes, alkenes, or alkynes are generated, hydrogenated, polymerized, or functionalized, metal alkyl intermediates are involved. It is estimated that about three quarters of all products of the chemical industry pass through a catalytic process at some stage. Most metal alkyl complexes containing donor ligands also follow the 18-electron rule. However, there are numerous complexes which are thermally quite stable but cannot be explained on the basis of the 18-electron rule. These compounds are often electronically highly unsaturated and owe their existence to the kinetic stabilization afforded by sterically demanding ligands. The chapter then considers the reactivity of metal alkyls, and looks at transition metal alkyl complexes in vivo.
Ultraviolet-visible spectroscopy
Authors: Harwood Laurence M. , Claridge Timothy D.W.
Published: September 2023

This chapter tells the history of the arrival of ultraviolet (UV) spectroscopic analysis during the 1930s, which was an important milestone in analytical chemistry. It demonstrated the advantages of non-destructive analysis. The chapter discusses the benefits brought by this development, such as vast savings in time, and the ability to work with much smaller samples of material, which demonstrated the power of spectroscopic analysis to organic chemists. The chapter also clarifies the restricted use of UV spectroscopy to specific areas of chemistry. These areas deal with compounds and have important absorption characteristics in the range of the electromagnetic spectrum. The chapter considers the UV-visible spectroscopy which outlines the major principles of absorption spectroscopy. It refers to the absorption of electromagnetic radiation in the UV-visible region which transfers the right amount of energy to cause transitions in the electronic energy levels of the bonds of a molecule.
Infrared spectroscopy
Authors: Harwood Laurence M. , Claridge Timothy D.W.
Published: September 2023

This chapter highlights the principles behind infrared spectroscopy, focusing on the energy range of the infrared rays. These cause vibrational excitation of bonds within a molecule. It discusses stretching for higher energy and bending lower energy as the types of bond excitation. It also refers to the absorption of certain wavelengths of infrared radiation which can be correlated with the bending or stretching of specific types of bonds within a molecule. The chapter analyses the infrared spectra of organic molecules. These are complicated by bond oscillations in the whole molecule and affect the absorption of the incident radiation—such absorption gives rise to overtones and harmonics. It mentions spectra recorded in solution or as a neat substance, which show complexity due to hydrogen bonding with solvents or the presence of dimeric or polymeric associated species..
Normal modes of vibration
Authors: Green N. J. B.
Published: September 2023

This chapter assesses normal modes of vibration. Normal coordinates with the same vibrational frequency are generally symmetry-related—they form a basis for a degenerate irrep of the point group. The reason underlying this observation is that the potential energy of the molecule is invariant to all symmetry operations of the molecular point group. If a molecule is distorted in some way, then a symmetry transformation from the point group of the equilibrium geometry must lead to a similar distortion with the same energy. The first step in the method for finding the symmetries of the normal modes of vibration is to set up a basis. This will be a coordinate system which can be used to describe all the possible ways in which the molecular geometry can be distorted. The chapter then looks at the symmetries of vibrational wavefunctions, as well as the vibrational spectra.
More metalloenzymes
Authors: Fenton David E.
Published: September 2023

This chapter explores more metalloenzymes, considering the enzymatic activity of zinc, cobalt, and molybdenum. Zinc is the second most abundant trace element in humans and is required as an integral component of over 100 enzymes in different species of all phyla. It can play an active catalytic role, generally as a strong Lewis acid, or it can act in regulatory or structural roles. The chapter then looks at trinuclear zinc constellations, vitamin B12, nitrogenases, and oxotransfer molybdoenzymes. Molybdenum is the only element from the second and third row transition metals that has been found to be essential to life. As well as functioning in nitrogenase, it has been found to be active in oxotransfer enzymes which catalyze the transfer of oxygen atoms to, or from, a substrate and are involved in carbon, nitrogen, and sulfur metabolism. The chapter also examines nickel enzymes.
Synthesis of amines
Authors: Bailey Patrick D. , Morgan Keith M.
Published: September 2023

This chapter looks into nitrogen bases. Nitrogen compounds are widely used as bases in organic synthesis. The chapter also looks into the types of nitrogen bases such as tertiary amines and metal amides. It also discusses the reactions employing nitrogen bases by referencing the absence of base, concerted removal of a proton, and giving an anionic intermediate. Diazabicyclo amines can help a proton leave as part of a concerted reaction. Additionally, the chapter notes deprotonation is usually conducted at low temperatures. It explains the good bases for mopping up protons while the most popular base for deprotonation is lithium diisopropylamide (LDA).
Imines
Authors: Bailey Patrick D. , Morgan Keith M.
Published: September 2023

This chapter explores the synthesis of amines. It explains how amines are accessible from three main sources: basic amine building blocks, synthetizsation of the amino group to a suitable precursor, and yielding more complex amines after being alkylated. Additionally, the chapter discusses the synthesis of amines through reduction reactions and substitution reactions via amines or ammonia. It also looks into using mononucleophilic ammonia using five widely used methods such as the classical Gabriel method. Next, the chapter looks at the two methods of preparing amines: are nucleophilic displacement using nitrogen from a nucleophilic source and reduction of a nitrogen-containing functional group. The chapter examinies the factors to consider when looking into unsaturated nitrogen compounds.
Amides
Authors: Bailey Patrick D. , Morgan Keith M.
Published: September 2023

This chapter discusses enamines. It explains the process of achieving enamine through regaining neutrality by losing a proton adjacent to the iminium moiety. Additionally, these compounds rarely serve as nucleophiles or bases on nitrogen. The chapter discusses the formation of enamines from amine and aldehyde or ketone. It highlights how electrophiles are required to be quite reactive as enamines are moderately nucleophilic. The chapter adds the hydrolysis of enamine which is an effort to regenerate the original secondary amine and reveal the carbonyl group. Also, it explores the tautomerism of using imines as enamines and vice versa.
Oximes
Authors: Bailey Patrick D. , Morgan Keith M.
Published: September 2023

This chapter discusses the synthesis and properties of compounds with N-N bonds. It looks into the synthesis and reaction of hydrazines, hydrazides, hydrazones, diazo compounds, and azides. The N-N-containing functional groups undergo vital interconversions which have great synthetic value. Additionally, the chapter explains how alkyl hydrazines are usually made from suitable alkyl halide and hydrazine. Also, hydrazones are prepared from the reaction of aldehydes and ketones with hydrazines, while oxidation of some hydrazines will result in the formation of diazo compounds. Alkyl azides are prepared via the nucleophilic attack of sodium azide on a suitable alkyl compound such as halide or sulphonate.
Nitroso compounds
Authors: Bailey Patrick D. , Morgan Keith M.
Published: September 2023

This chapter looks into the synthesis and reactions of N-oxides. The N-heteroatom bond of N-oxides is not introduced intact in the synthesis of compounds. However, it is delivered in an oxidation reaction. It notes peracid as the usual oxidant which is either used directly or generated in place from a carboxylic acid or hydrogen peroxide mixture. It also highlights how N-oxides are vital for aeffecting
syn
eliminations as the N-oxide acts similarly to a quaternary ammonium compound with an internal alkoxide base. Finally, the chapter uses diagrams to emphasise how the synthesis and reactions occurs.
Further reading
Authors: Bailey Patrick D. , Morgan Keith M.
Published: September 2023

Organonitrogen chemistry is an integral part of all mainstream organic textbooks. It also features strongly in books on synthesis, mechanism, reactivity, natural products, and more specific classes of compounds. Indeed, several aspects of organonitrogen chemistry from this book also feature in other OUP primers. However,...
Electronic spectroscopy
Authors: Brown John M.
Published: September 2023

This chapter covers spectroscopy involving the excitation of an electron from one state to another. It talks about how electronic transitions occur at longer wavelengths and are often seen in the visible state as the separation of electronic energy levels of open-shell molecules is typically small. It also mentions the characteristic potential energy curve of the electronic state that supports its own set of vibrational and rotational levels, emphasizing that electronic transitions involve a change of associated vibrational and rotational quantum numbers. The chapter defines the quantum numbers of the electronic wavefunction. It describes an electron as a fundamental particle with a very small mass, which requires a full quantum mechanical treatment.
Retrosynthetic analysis II: Latent polarity and FGIs
Authors: Willis Christine L. , Wills Martin
Published: September 2023

This chapter examines latent polarity and functional group interconversions (FGIs). In the previous chapter, the basic concepts of retrosynthetic analysis were introduced, and the importance of polarity highlighted. The reactivity of unsaturated carbonyl compounds introduces the use of a further pattern of efficient syntheses of target molecules. The best disconnections of target alcohol shown in the previous chapter led to synthons which had an alternating pattern of charges as we move away from the hydroxyl or carbonyl group, starting with a positive charge on the carbon adjacent to oxygen. Writing this alternating pattern of imaginary charges or ‘latent polarities’ on a target molecule can greatly assist the identification of potential synthons since breaking a bond in the retrosynthetic direction immediately gives viable synthons, for which corresponding reagents are available.
Basic crystallography
Authors: Weller Mark T.
Published: September 2023

This chapter provides a background of crystallography. The structures of inorganic materials, the majority of which are crystalline in the solid state, are a key feature in the control of their chemistry and physical properties. The techniques used to identify and investigate such materials involve characterization of the bulk structure. The chapter begins by looking at crystal systems and unit cells; fractional atomic coordinates and projections; lattices; Bravais lattices; and lattice lines and planes, which are labelled using the Miller indices. It then explains X-ray diffraction. The scattering of X-rays from crystalline solids can be demonstrated by consideration of the diffraction from points on a set of lattice planes. Finally, the chapter details the powder technique, outlining the different methods of obtaining powder X-ray diffraction data.
The synthesis of inorganic materials
Authors: Weller Mark T.
Published: September 2023

This chapter examines the synthesis of inorganic materials. The synthesis methods used in the preparation of inorganic materials, many of which have extended lattices rather than discrete molecules, are quite different from those used by organic, organometallic, and coordination chemists. Rather than altering a single functional group or ligand attached to a molecule, the materials chemist works with complete lattices, either building or modifying them. The chapter begins by looking at high temperature reactions. The most widely used method for the synthesis of inorganic materials follows an almost universal route that involves heating the components together at high temperature over an extended period. The chapter then details the process of the reaction between solids, before studying the precursor, solution, and gel methods. It also assesses hydrothermal methods, phase diagrams, and low temperature methods.
Introduction
Authors: Ward Robert S.
Published: September 2023

This chapter provides a background on organic compounds containing two or more functional groups. These can have a similar chemistry to the corresponding monofunctional compounds, but in some cases, the combination of different functional groups gives rise to modified or unique chemical and physical properties. For example, the carbon-carbon double bond of an αβ-unsaturated carbonyl compound readily undergoes addition by nucleophiles although alkenes usually react only with electrophiles. The chapter also cites the carbon-carbon double bond of an enamine that is strongly nucleophilic as it reacts with alkyl halides. The chapter explains that bifunctional compounds can be classified according to the nature of the groups present and their relative position and introduces naming conventions.
Reactions of dicarbonyl compounds
Authors: Ward Robert S.
Published: September 2023

This chapter discusses α-dicarbonyl compounds that undergo rearrangement on treatment with alkali, which provides a useful synthetic route to some α-hydroxyacids. It highlights the mechanism that involves the addition of hydroxide to one of the carbonyl groups, followed by the migration of one of the alkyl or aryl substituents to the second carbonyl group. It also covers the contrast ofcontrasts the structure of 2,3-butanedione, which almost entirely exists in the diketo form, and with the structure of 1,2-cyclopentanedione, which exists as the enol. The chapter illustrates how 2,3-butanedione can adopt an anti confirmation conformation with two carbonyl dipoles, while in the diketo form, 1,2-cyclopentanedione is forced to adopt a structure wherein there is a strong repulsive interaction between two carbonyl groups. The chapter alsoIt discussesrefers to β-dicarbonyl compounds, that which exist in equilibrium with their enol tautomers and in some solvents, and their reactions.
Reactions of unsaturated carbonyl compounds
Authors: Ward Robert S.
Published: September 2023

This chapter reviews ketenes, which undergo two characteristic reactions that are also typical of heterocumulenes. It talks about nucleophilic addition and cycloaddition, reactions with nucleophiles that result in acetylation of the nucleophilic reagent. It also mentions the cycloaddition reactions of ketenes, which are similar to the Diels-Adder reactions, although they are classified as [2+2] cycloaddition reactions. The chapter analyses the chemistry of αβ-unsaturated carbonyl, which is dependent upon the interaction between the orbitals of the carbon–carbon double bond and those of the carbon–oxygen double bond. It describes the influence of the electron-withdrawing carbonyl group on the reactivity of the carbon–carbon double bond.
Allyl and dienyl complexes
Authors: Bochmann Manfred
Published: September 2023

This chapter focuses on allyl and dienyl complexes. The allyl ligand is the simplest in a series of non-cyclic conjugated anionic (enyl) ligands. Coordinated allyl is susceptible to nucleophilic attack—a property which has made allyl complexes invaluable in synthesis and is the basis of numerous catalytic reactions. The site of nucleophilic attack depends on the nature of the metal: allyl groups with cationic character are attacked in the 1,3-position, while anionic allyls react in the 2-position. The chapter then looks at the synthesis and reactivity of allyl complexes, before studying enyl complexes. Dienyl complexes, particularly iron tricarbonyl compounds, have important applications in stereoselective synthesis.
Arene complexes
Authors: Bochmann Manfred
Published: September 2023

This chapter assesses arene complexes. Following the recognition in the early 1950s of the sandwich bonding principle for metallocenes, the existence of related sandwich complexes of neutral arenes such as benzene was demonstrated through the synthesis of bis-(benzene)chromium. The complex is isoelectronic to ferrocene and follows the 18-electron rule. Bonding in bis-(arene)metal complexes resembles that in metallocenes, and the MO diagram is qualitatively very similar. Since the aromatic ligands in bis-(arene) complexes are not negatively charged, there is no electrostatic contribution to bonding, and bis-(arene) complexes are in general less stable than metallocenes and more easily oxidized. The chapter then considers arene half-sandwich complexes; seven and eight membered ring ligands; heteroarene complexes; and multidecker complexes.
Organic reaction mechanisms and reaction maps
Authors: Maskill Howard
Published: September 2023

This chapter discusses organic reaction mechanisms and reaction maps. Collisions between molecules provide the energy for bimolecular and unimolecular thermal reactions to occur. In a bimolecular reaction, three translational and (normally) up to three rotational degrees of freedom are lost in the formation of the activated complex; since the total has to remain the same, a corresponding number of new vibrational degrees of freedom are formed. In a unimolecular reaction, a molecular collision leaves one of the molecules in a vibrationally excited state which either reacts or simply loses its excess energy in a subsequent collision. The chapter then looks at molecular vibrations and potential energy diagrams. It also considers parallel and perpendicular effects; step-wise reactions; and single-step multibond cycloaddition reactions.
Introduction
Authors: Davis Benjamin G. , Fairbanks Antony J.
Published: September 2023

This chapter provides a background on the term carbohydrate. The initial understanding of the term originated in the nineteenth century. It comes from the French for the family of compounds that possess an empirical formula. The chapter discusses how the term carbohydrate has been since extended to encompass other materials. It also describes carbohydrates to be polyhydroxylated aldehydes that contain a number of carbon atoms which vary in number between 3 and 9. The chapter considers glucose as the most abundant organic molecule on the planet. An example is cellulose. This is a polymer of glucose and DNA and RNA. The chapter illustrates the importance of the varied roles of sugars and shows that a consideration of sugar chemistry should go hand-in-hand with a knowledge of the biological importance of sugars.