What are HYDROCARBONS?

A Hydrocarbon is an organic compound consisting of Hydrogen and Carbon. The greater part of hydrocarbons found on earth naturally occur in crude oil, where decaying organic matter provides an abundance of carbon and hydrogen which, when bonded, can catenate to form seemingly boundless chains.

 Classified into two(2) :

1. ALIPHATIC HYDROCARBONS

   - It consist of linear chains of carbon atoms.
   -  The simplest aliphatic hydrocarbon is Methane (CH₄)   
     
   Under Aliphatic Hydrocarbons,

                

    1.      Alkanes (paraffin) 

        -  are the simplest of the hydrocarbon species. They are also  called saturated hydrocarbons  since they are composed totally of single  bonds and are saturated with hydrogen.

    2.   Alkenes (olefins) 

         – They are also called unsaturated hydrocarbon (hydrocarbons having one or more  double or  triple bonds between carbon atoms). 

   Alkenes are mainly composed of double bonds.

        3.        Alkynes 

                             

         – are composed of triple bonds and it is also                                                  unsaturated hydrocarbons.

     

     2. AROMATIC HYDROCARBONS

                   

  - It consist of closed rings of carbon atoms.

  - Also known as arenes, are hydrocarbons that have at least                            one aromatic ring.

  - Its building blocks are benzene rings.

  - The simplest aromatic hydrocarbon is benzene, which is simply a                  ring.

  - Can be classified as monocyclic or polycyclic hydrocarbons.

    Under the aromatic hydrocarbons, 

      

      Cycloalkanes

      - are hydrocarbons containing one or more carbon rings

             to which hydrogen atoms are attached.

(Types of Aliphatic Hydrocarbons)

ALKANES

- Hydrocarbons that contain only single bonds.

- Have a general formula of  CnH2n+2

- The first four Methane, Ethane, Propane, Butane

Characteristics:

•      highly combustible
•      valuable as clean fuels
•      Alkane derivatives are used in hundreds of products such as plastics, paints, drugs, cosmetics, detergents, insecticides, etc.,

Number of Carbons	Prefix	Structure
1	Methane	CH4
2	Ethane	CH3CH3
3	Propane	CH3CH2CH3
4	Butane	CH3(CH2)2CH3
5	Pentane	CH3(CH2)3CH3
6	Hexane	CH3(CH2)4CH3
7	Heptane	CH3(CH2)5CH3
8	Octane	CH3(CH2)6CH3
9	Nonane	CH3(CH2)7CH3
10	Decane	CH3(CH2)8CH3
11	Undecane	CH3(CH2)9CH3

ALKENES: -          General formula:  CnH2n -          Aliphatic hydrocarbons with one double bond between carbons. They follow the naming convention of the alkanes except that the suffix -ene is used instead of -ane. For alkenes above propene the position of the double bond must be specified in the name.

Alkenes are unsaturated hydrocarbons and are generally very reactive. Typical reactions involve the addition of hydrogens or halogens.

The double bond in alkenes can act to bond such molecules together in long chains and sheets. The formation of polymers is an important area of chemistry. 

ALKYNES: 

    - comprise a series of carbon‐ and hydrogen‐based compounds that contain at least one triple bond. This  group of compounds is a homologous series with the general molecular formula of C _n H _{2 n‐‐2} , where n equals any integer greater than one.

-       The simplest alkyne, ethyne (also known as acetylene), has two carbon atoms and the molecular formula of C ₂H ₂. The structural formula for ethyne is

In longer alkyne chains, the additional carbon atoms are attached to each other by single covalent bonds. Each carbon atom is also attached to sufficient hydrogen atoms to produce a total of four single covalent bonds about itself. In alkynes of four or more carbon atoms, the triple bond can be located in different positions along the chain, leading to the formation of structural isomers. For example, the alkyne of molecular formula C ₄H ₆ has two isomers,

Although alkynes possess restricted rotation due to the triple bond, they do not have stereoisomers like the alkenes because the bonding in a carbon‐carbon triple bond is sp hybridized. In sp hybridization, the maximum separation between the hybridized orbitals is 180°, so the molecule is linear. Thus, the substituents on triple‐bonded carbons are positioned in a straight line, and stereoisomers are impossible. 

Aromatic Hydrocarbons

The building block of aromatic hydrocarbons is the benzene ring.

The arrangement of atoms is shown on the left. The version in the center is often used to simplify diagrams of molecular structures.
The three double bonds are not restricted to the positions shown but are free to pass around the ring. This is sometimes indicated by drawing the benzene ring as it is on the far right.

Some examples of biological molecules that incorporate the benzene ring:

•       The amino acids tyrosine and phenylalanine
•       cholesterol and its various derivatives, such as the sex hormones
•       estrogens
•      testosterone
•        the herbicide, 2,4-D

The carotenoid, beta-carotene, is a hydrocarbon that has both aliphatic and aromatic portions.