Revision: Class 11 >> Hydrocarbons NEET (UG) Hydrocarbons

Saturated hydrocarbons (containing a single bond) are called ‘Alkanes’.

Hydrocarbons are compounds that 9re made up only of carbon and hydrogen atoms.

OR

The compounds which contain carbon and hydrogen as the only two elements are called hydrocarbons.

Saturated hydrocarbons are hydrocarbons in which the valencies of all atoms are satisfied by single bonds.

The unsaturated hydrocarbons containing a carbon-carbon double bond are called ‘Alkenes’.

The unsaturated hydrocarbons whose structures contain a carbon-carbon triple bond are called ‘Alkynes’.

The hydrocarbons that have double or triple covalent bonds between two adjacent carbon atoms are called unsaturated hydrocarbons.

OR

The carbon compounds having a double bond or triple bond between two carbon atoms are called unsaturated compounds. Ethene and ethyne are unsaturated hydrocarbons.

The compounds of carbon having double or triple bonds between the carbon atoms are known as unsaturated carbon compounds.

The valencies of all the atoms are satisfied by single bonds between them. Such carbon compounds are called saturated compounds.

Alkanes are hydrocarbons in which all the linkages between the carbon atoms are single covalent bonds.

Alkenes are compounds with at least one carbon-carbon double bond. Alkenes form a homologous series having the general formula C_n H_2n

Compounds having the same molecular formula but different structural formula are known as Isomers and the phenomenon is known as Isomerism. (iso = same, meros = parts).

The aliphatic hydrocarbons that contain a triple bond (-C = C-), i.e., acetylenic bond, between two carbon atoms are known as alkynes. The general formula C_nH_2n-2.

• Hydrocarbons contain only carbon and hydrogen atoms and are the basic type of organic compounds.
• Saturated hydrocarbons have single bonds (e.g. methane, ethane, propane).
• Unsaturated hydrocarbons have double or triple bonds (e.g. ethene, ethyne).
• To draw structures, join the carbon atoms first, then add hydrogen atoms to complete 4 bonds per carbon.
• Ethene has a double bond, and ethyne has a triple bond between carbon atoms.

• Ethene is a colourless, flammable gas with a faint, sweet smell.
• It has a melting point of –169°C and boiling point of –102°C.
• Slightly soluble in water but highly soluble in organic solvents; has a mild anaesthetic effect.

• Ethene reacts with hydrogen, halogens, and acids to form saturated compounds like ethane and alcohols.
• It forms polythene through polymerisation.
• Burns with a sooty flame and gives ethylene glycol with KMnO₄.