Carbon atom bonding characteristics. Carbon atoms in organic compounds must have four bonds.

Types of hydrocarbons. Hydrocarbons, binary compounds of carbon and hydrogen, are of two types: saturated and unsaturated. In saturated hydrocarbons, all carbon - carbon bonds are single bonds. Unsaturated hydrocarbons have one or more carbon - carbon multiple bonds - double bonds, triple bonds, or both.

Alkanes. Alkanes are saturated hydrocarbons in which the carbon atom arrangement is that of an unbranched or branched chain. The formulas of all alkanes can be represented by the general formula CnH2n+2, where n is the number of carbon atoms present.

Structural formulas. Structural formulas are two-dimensional representations of the arrangement of the atoms in molecules. These formulas give complete information about the arrangement of the atoms in a molecule but not the spatial orientation of the atoms. Two types of structural formulas are commonly encountered: expanded and condensed.

Structural isomerism. Structural isomers are two or more compounds that have the same molecular formula but different structural formulas - that is, different arrangements of atoms within the molecule.

Conformations. Conformations are differing orientations of the same molecule made possible by free rotation about single bonds in the molecule.

Alkane nomenclature. The IUPAC name for an alkane is based on the longest continuous chain of carbon atoms in the molecule. A group of carbon atoms attached to the chain is an alkyl group. Both the position and the identity of the alkyl group are prefixed to the name of the longest carbon chain.

Cycloalkanes. Cycloalkanes are saturated hydrocarbons in which at least one cyclic arrangement of carbon atoms is present. The formulas of all cycloalkanes can be represented by the general formula CnH2n, where n is the number of carbon atoms present.

Cycloalkane nomenclature. The IUPAC name for a cycloalkane is obtained by placing the prefix cyclo- before the alkane name that corresponds to the number of carbon atoms in the ring. Alkyl groups attached to the ring are located by using a ring-numbering system.

Cis - trans isomerism. For certain disubstituted cycloalkanes, cis - trans isomers exist. Cis - trans isomers are compounds that have the same molecular and structural formulas but different arrangements of atoms in space because of restricted rotation about bonds.

Natural sources of saturated hydrocarbons. Natural gas and petroleum are the largest and most important natural sources of both alkanes and cycloalkanes.

Physical properties of saturated hydrocarbons. Saturated hydrocarbons are not soluble in water and have lower densities than water. Melting and boiling points increase with increasing carbon chain length or ring size.

Chemical properties of saturated hydrocarbons. Two important reactions that saturated hydrocarbons undergo are combustion and halogenation. In combustion, saturated hydrocarbons burn in air to produce CO2 and H2O. Halogenation is a substitution reaction in which one or more hydrogen atoms of the hydrocarbon are replaced by halogen atoms.