Draw the structures of the nine isomeric heptanes `(C_7H_(16))`.
Strategy: start with the straight chain isomer (longest chain). Going to a six-carbon chain, a `CH_3` may be placed either on `C-2` or on `C-3` to give two isomers. Starting with a five-carbon chain, either two `CH_3`, or a `CH_3CH_2` must be added as side chain for a total of seven C's. The two `CH_3` may be placed on the same C atom or on different carbons giving a total of four isomers. The `CH_3CH_2` group can only be placed on the central C atom. At other points it either lengtherns the chain or reproduces previous isomer.Finally, go for a four carbon chain and three `CH_3`'s to form the ninth isomer.

Options

A. eight
B. Seven
C. nine
D. six

Answer

C

Explanation

Start with the longest chain of 7 C atoms and end up with four-carbon chain with different possiblities of branches. For further details.