Logo : organicmystery.com Online Organic Chemistry Tutorial

Hydrocarbons Introduction

«Previous Next »

Hydrocarbons

Organic compounds containing only carbon and hydrogen atoms are called hydrocarbons.

Classification of hydrocarbons

Depending upon the type of carbon-carbon bonds present, they can be classified into the following three categories :

  1. Saturated hydrocarbons
  2. Unsaturated hydrocarbons
  3. Aromatic hydrocarbons

Saturated hydrocarbons

Saturated hydrocarbons contain only carbon-carbon single bonds. In other words, there is no double or triple bonds present in the compound.

If different carbon atoms of saturated hydrocarbons are linked together to form open chain, they are termed as alkanes. On the other hand, if carbon atoms form a closed ring, they are termed as cycloalkanes.

Saturated hydrocarbons

2-Methylpropane

Saturated hydrocarbons example : alkane

2,2-Dimethylpropane

Alkane example

Ethane

Alkane example : Ethane

Cyclohexane

Closed ring example : Cyclohexane

Unsaturated hydrocarbons

Hydrocarbons containing at least one carbon-carbon multiple bond (double or triple) are termed as unsaturated hydrocarbons. Study the following important points :

Unsaturated hydrocarbons

Ethene

Unsaturated hydrocarbons example : Ethene

Ethyne

Alkyne example

Cyclohexene

Closed ring example : Cyclohexene

Cyclohexyne

alicyclic ring example : Cyclohexyne

Cyclohexen-3-yne

cyclic ring example : Cyclohexen-3-yne

Buten-3-yne

Alkyne example : Buten-3-yne

Aromatic hydrocarbons

Aromatic hydrocarbons are a special type of cyclic compounds. Most of aromatic compounds contain benzene ring and are known as benzenoids. However, there are some examples of aromatic hydrocarbons that do not contain benzene but instead contain other highly unsaturated ring. Such compounds are termed as non-benzenoids.

Aromatic hydrocarbons

Benzene

Aromatic hydrocarbons example : Benzene

Toluene

Aromatic hydrocarbons example : Toluene

Primary, secondary, tertiary and quaternary carbons

Based upon the number of carbon atoms attached to a carbon, the carbon atom is termed as primary (1°), secondary (2°), tertiary (3°) and quaternary (4°) carbon .

  1. Primary carbon (1°) : A carbon atom attached to one or no carbon atom is known as primary carbon or 1° carbon.
  2. Secondary carbon (2°) : A carbon atom attached to two other carbon atoms is called a secondary (2°) carbon.
  3. Tertiary carbon (3°) : A carbon is termed as tertiary carbon (3°) if it is attached to three other carbon atoms.
  4. Quaternary carbon (4°) : A carbon is termed as quaternary (4°) carbon if it is attached to four other carbon atoms.

The hydrogen atoms attached to primary, secondary and tertiary carbon atoms are termed as primary, secondary and tertiary hydrogen atoms. Since a quaternary carbon does not contain any hydrogens, there is nothing like quaternary hydrogen atoms. Take a look at the following example :

primary secondary tertiary and quaternary carbon atoms

Nomenclature of hydrocarbons

There is a separate section on nomenclature of organic compounds. Refer to Nomenclature of Organic Compounds to learn nomenclature.

«Previous Next »