Alkanes are hydrocarbons where all carbons are joined by
single bonds.
CH3CH2CH3 (C3H8) is an example of an alkane.
Alkanes may have any number of carbons, but the general formula is always CnH2n+2.
Carbon atoms may also be joined by
multiple bonds.
In ethene (H2C=CH2) the carbon atoms share four electrons in a double bond.
This is represented by two lines between the bonded atoms.
In ethyne (HC≡CH) the carbon atoms share six electrons in a triple bond.
This is represented three lines between the bonded atoms.
Alkenes are hydrocarbons that have a
carbon-carbon double bond.
CH3CH=CH2 (C3H6) and CH3CH=CHCH3 (C4H8) are examples of alkenes.
Alkenes have fewer hydrogens than alkanes and their general formula is CnH2n.
Alkynes are hydrocarbons that have a
carbon-carbon triple bondCH3C≡CH (C3H4) and CH3C≡CCH3 (C4H6) are examples of alkynes.
Alkynes have fewer hydrogens than either alkanes or alkenes, and their general formula is CnH2n-2.
Compounds are referred to as
saturated because they have maximum number of hydrogens are attached to each atom.
Compounds that have fewer than the maximum number are referred to as unsaturated.
Ethene and ethyne are unsaturated.
The formulae for alkanes, alkenes and alkynes forms a homologous series.
Each member of each of these series differs from the one before and the one another by a CH2.
For alkanes: CH4, C2H6, C3H8, C4H10 and so on.