Hydrocarbons

04 Carbon and its compound

• Carbon forms a number of compounds due to its salient properties.
• Methane (CH4) is the most general or basic compound.
• Hydrocarbon is the compound made up of just hydrogen and carbon and so methane is a hydrocarbon.
• Hydrogen + Carbon = Hydrocarbon
• As ethane (C2H6), ethylene (C2H4), and ethyne (C2H2), are other hydrocarbons as they are made up of only two elements: Carbon and Hydrogen, they are called as Hydrocarbons.
• The most important natural source of hydrocarbons is petroleum (or crude oil).
• The molecular formula of such compounds can be easily determined by adding hydrogen to satisfy the valency of carbon atoms.
• For example: ethane has two carbon atoms. So 6 hydrogen atoms are required to satisfy the valency of each carbon atom. Hence the molecular formula for ethane is C2H6.

TYPES OF HYDROCARBONS

• Hydrocarbons are of two types:
• Saturated hydrocarbons and
• Unsaturated hydrocarbons.

SATURATED HYDROCARBONS (ALKANES)

• In Saturated hydrocarbon the carbon atoms are connected by only single bonds.  4

ALKANES

• Saturated hydrocarbons are also known as alkanes.
• There are no double or triple bonds in an alkane as alkane is a saturated hydrocarbon in which the carbon atoms are connected by only single covalent bonds
• The hydrocarbons methane, ethane, propane and butane form a series of compounds known as alkanes. The structure of ethane is shown below:
• Naming Convention: The names of all these saturated hydrocarbons end with ‘ane’.
• Formula: The saturated hydrocarbons or alkane is represented as: CnH2n+2Where n is the number of carbon atoms is one molecule of the alkane.

UNSATURATED HYDROCARBONS (ALKENES AND ALKYNES)

• In Unsaturated hydrocarbon two carbon atoms are connected by a ‘double bond’ or a ‘triple bond’.
• Unsaturated hydrocarbons are of two types:
• Alkenes: Those containing carbon-carbon double bonds.
• Alkynes: Those containing carbon-carbon triple bonds.

ALKENES

• An alkene is an unsaturated hydrocarbon where two carbon atoms are connected by a soluble bond.
• Alkene has a double bond between two carbon atoms. So, it is obvious that the simplest alkene will have two carbon atoms in its molecules.
• Hence, there can be no alkene having only one carbon atom.
• Formula: The general formula of an alkene is CnH2n , where n is the number of carbon atoms in its one molecule.
• The simplest alkene is ethene having the molecular formula. The common name of ethene is ethylene.

ALKYNES

• Alkyne is an unsaturated hydrocarbon where two carbon atoms connect to form a triple bond..
• Formula: The general formula of alkynes is CnH2n-2, where n is the number of carbon atoms in one molecule of the alkyne.
• The simplest alkyne is ethyne having the molecular formula. The common name of ethyne is acetylene.