Introduction In Organic chemistry

Introduction

In Organic chemistry, a hydrocarbon is an organic compound that consists only hydrogen and carbon. Hydrocarbon can be formed as double or triple bond and even as a structure, such as rings to form. It is the principal constituents of natural gas and petroleum. It is used as many raw material as well as lubricants and fuels for the production of rubbers, plastics, industrial chemical and other materials. Many hydrocarbons can be found in nature. In order to making up fossil fuels, they are present in plants. Example of natural hydrocarbon would be pigments called carotenes that occur in carrots and green leaves, Natural rubber is a also good hydrocarbon polymers. The structures and chemistry of individual hydrocarbons depend in extensive part on the kinds of chemical bonds that rb

Types of hydrocarbon

Nineteenth Century scientist categorized ‘Hydrocarbon’ as either aliphatic aromatic hydrocarbon on the basis of its sources , physical and chemical properties. Aromatic hydrocarbons constituted a group of related substances obtained by chemical degradation of certain pleasant-smelling plant extracts. The terms aliphatic and aromatic are retained in modern terminology, but the compounds they define are describe on the basis of structure rather than origin.

i) Aliphatic hydrocarbon
It is mainly divided into three group according to the types of bonds which are alkanes, alkenes, and alkynes. Alkane only has a single bond, where alkenes and alkynes consist of double and triple bonds. Aromatic bond is more stable than their Lewis structures might suggest; i.e., they possess “special stability.”
They are classified as either arenes, that contain a benzene ring as a structural unit, or non-benzenoid aromatic hydrocarbons, that possess strong stability but lack benzene ring.

Alkanes are called as saturated hydrocarbon where alkenes, alkynes and aromatic hydrocarbons are defined as unsaturated hydrocarbon.

Alkanes

Alkanes are hydrocarbons that consist only single bond and the molecular formula of alkanes is CnH2n + 2 (where n is an integer). Carbon is basically sp3 hybridized. Methane is one of the prime example of saturated hydrocarbon. It is basically a gas from decomposing bodies and intestinal tracts of other animals. This is the simples hydrocarbon and has the formula of CH4. The structure of it is shown below:

There are some other saturated carbon just like methane. For instance : ethane (C2H6), propane (C3H8), butane (C4H10) and pentane (C5H12). They add one carbon to the chain.

The structure formula of some of the alkanes shown on the table below

Different compounds containing simillar molecular formula are known as isomers. Isomer differing in the order where atoms are attached and have different constituions are reffered as constituonal isomers. It is also known as structural hydrocarbon. Because isomers are not the exact same compound , they can have different physical and chemical compound. For instance the boiling point of n-butane (31°F) is higher than iso-butane (-11.7°F) . There are no easy arithmetic theory between the number of carbon atoms in a formula and isomers number. Graph theory has been used occassionaly to calculate number of constitutional isomeric alkanes. The number of constitutional isomer increases if the numer of carbon atom increases as well.

Number of possible alkane isomers
molecular formula number of constitutional isomers
C3H8 1
C4H10 2
C5H12 3
C6H14 5
C7H16 9
C8H18 18
C9H20 35
C10H22 75
C15H32 4,347
C20H42 366,319
C30H62 4,111,846,763

Physical properties of Alkanes

The first four Alkanes are methane, ethane, propane, and butane are all gases. The next fifteen are colorless liquids. (C5-C19). Any alkanes higher than that are wax like solids