Hydrocarbon

Hydrocarbon are those organic compounds which contain carbon and hydrogen only. Typically, hydrocarbons are colourless gases that have very weak odours. Hydrocarbons can feature simple or relatively complex structures and can be generally classified into four subcategories, namely alkanes, alkenes, alkynes, and aren’t. The study of hydrocarbons can provide insight into the chemical properties of other functional groups and their preparation. Furthermore, hydrocarbons such as propane and butane are used for commercial fuel purposes in the form of Liquefied Petroleum Gas (LPG). Benzene, one of the simplest aromatic hydrocarbons, serves as raw material for the synthesis of many synthetic drugs.
==Classification==
Older chemists classified hydrocarbons as either aliphatic or aromatic. The classification was done based on their source and properties. As such, it was found out that Aliphatic hydrocarbons were derived from chemical degradation of fats or oils whereas aromatic hydrocarbons contained substances that were a result of chemical degradation of certain plant extracts. However, today we classify hydrocarbons on the basis of structure and not merely on the origin.
Image:Classification-of-Hydrocarbons.png|720px|frameless|center|henlo
rect 52 107 159 129 Hydrocarbon#Acyclic
rect 1 195 60 210 Hydrocarbon#Saturated
rect 140 199 209 216 Hydrocarbon#Unsaturated
rect 382 112 434 130 Hydrocarbon#Alicyclic
rect 297 195 373 216 Hydrocarbon#Homocyclic
rect 436 196 518 216 Hydrocarbon#Heteracyclic
rect 223 285 281 304 Hydrocarbon#Aromatic
rect 290 283 373 299 Hydrocarbon#Non-aromatic
rect 377 289 465 302 Hydrocarbon#Anti-aromatic
==Types==
===Saturated===
In these compounds, carbon-carbon atoms and carbon-hydrogen atoms are held together by single bonds. These single bonded compounds are the simplest hydrocarbons. These types of hydrocarbons don’t have double or triple bonds. In terms of hybridization, they have Sp3 hybridised carbon atom with no Sp or Sp hybridised Carbon atoms. They are together called as alkanes which have a general formula CH. For example, CHCH.
===Unsaturated===
These compounds consist of a single, double or a triple bond between carbon-carbon atoms. The double-bonded compounds are called alkenes and the triple bonded compounds are called alkynes. The general formula for alkenes is CH and for alkynes the general formula is CH.
===Aromatic===
These are also called as arenes. Arenes are compounds which consist of at least one aromatic ring.
===Alicyclic===
They are hydrocarbons having a ring structure in them. The carbons atoms can be Sp, Sp or Sp hybridised.
==Properties==
Due to their different molecular structures, the empirical formula of hydrocarbons is also different from each other. For instance, alkanes, alkynes or alkenes, the amount of bonded hydrogen decreases in alkenes and alkynes. This is mainly due to the “self-bonding” or catenation of carbon that prevents the complete saturation of the hydrocarbon by the formation of double or triple bonds. The ability of hydrocarbons to bond to themselves is known as catenation. With such capabilities, they can form more complex molecules like cyclohexane and in rare instances aromatic hydrocarbons like benzene.
Meanwhile, cracking of Hydrocarbons is a process in which heavy organic molecules are broken down into lighter molecules. This is accomplished by supplying an adequate amount of heat and pressure. Sometimes catalysts are used to speed up the reaction. This process plays a very important role in the commercial production of diesel fuel and gasoline.
===Physical Properties===
Alkanes with 10 C-atoms or less are generally gases at room temperatures more than 10 C-atoms, the molecules are gases or liquid. Alkanes generally having low boiling and melting points owing to their weak Vanderwal’s interaction.
Boiling point depends on a molecular mass and Branching.
Alkanes having high molecular mass and high boiling points. Eg: C_2H_6 has more boiling point than CH_4.
Alkanes having same molecular mass but having a different number of branches, the one with less branching has more boiling point this is because of the Vanderwal’s force weak on as area increases.
For example, CH-CH-CH-CH has more Boiling point. Alkanes are very feebly soluble in water but they are soluble in non-polar solvents such as Benzene, CCl, etc.
==Preparation==
===From alkenes and alkynes===
The alkanes can be produced from alkenes or alkynes through hydrogenation. H gas is passed over a metal surface such as Ni, Pt along with the alkenes to produce alkane.
 CH_2=CH_2 \xrightarrow{[+Hz/Ni]} CH_3-CH_3
The above reaction is called as “Sabatier-Sender son’s” reaction. Other catalysts which can be used are Pt, Pd-BaSo, Adams catalyst (PtO) or Wilkinson catalyst (RPRhCl).
===From Alkyle Halides===
Alkyl halides can be converted to alkanes through various methods. 
* Using Zn/Protic solvents
* Using courts reactions
* Using Reducing Agents: R-X \xrightarrow{H} R-H 
The reducing agents which can be used are LiAlH4, NaBH4, NaNH2, etc.
Category:Organic chemistry