Question

A.
Select the correct structure that
corresponds to the name.
heptane
B.
CH3(CH2)4CH3

Answer 1

Answer:

Only A., the stick structure with no branches and five vertices between the two endpoints.

Explanation:

An alkane is a saturated hydrocarbon compound with no branches- just a series of carbon atoms connected with ${\rm C}-{\rm C}$ single bonds. Heptane is the name for an alkane with $7$ carbon atoms (the prefix "$\verb!hept-!$" means "seven".)

Notice that there are only $6$ carbon atoms in the alkane with the condensed structure formula ${\rm CH_{3}}({\rm CH_{2})_{4}{\rm CH_{3}}$. The name for that structure would be hexane, not heptane.

In general, the condensed structure formula of an alkane with $n$ carbon atoms ($n > 2$) is ${\rm CH_{3}}({\rm CH_{2}})_{n-2} {\rm CH_{3}}$. The correct condensed structure formula for heptane ($n = 7$) would be ${\rm CH_{3}}({\rm CH_{2}})_{5} {\rm CH_{3}}$.

The structure in choice A is represented as a line-angle formula. As long as no letter is present in the formula, each vertex in the line-angle formula (including the endpoints) represents a carbon atom. Hence, the line-angle formula in choice A would represent a hydrocarbon with $7$ carbon atoms.

A single line denotes a single bond between atoms. All $7$ carbon atoms in this structure are thus joined in a line with ${\rm C}-{\rm C}$ single bonds. Hence, this structure denotes an alkane with $7$ carbon atoms- heptane.