2. I. AN INTRODUCTION
Alkanes are aliphatic hydrocarbons having only C-C
and C-H σ bonds. Because their carbon atoms be joined
together in chains or rings, they can be categorized as acylic
or cyclic.
- Acyclic alkanes have the molecular formula CnH2n+2
(where n = integer) and contain only linear and branched
chains of carbon atoms. They are also called saturated
hydrocarbons because they have maximum number of
hydrogen atoms per carbon.
- Cycloalkanes contain carbons joined in one or more rings.
Because their general formula is CnHn, they have two fewer
hydrogen atoms than an acylic alkane with the same number
of carbon.
3.
4. II. ACYCLIC ALKANES HAVING ONE TO FIVE
CARBON ATOMS
Methane, CH4, has a single carbon atom, and ethane,
CH3-CH3, has two. All C atoms are surounded by four
groups, making them sp3 hybridized and tetrahedral, and
all bond angles are 109.5o.
5.
6. The three-carbon alkane CH3CH2CH3, called propane,
molecular formula C3H8.
10. Butane and isobutane are isomers, two different
compounds with the same molecular formula. They belong
to one of two major classes of isomers called constitutional
or structural isomers.
11. With alkanes having more than four carbons, the names
of the straight-chain isomers are systematic and derive
Greek roots: pentane for five C atom, hexane for six, and so
on. There are three constitutional isomers for five-carbon
alkane, each having molecular formula C5H12: pentane,
isopentane (or 2-methylbutane), and neopentane (or 2,2-
dimethylpropane).
