Question

How many five carbon alkyl groups are possible(pentyl isomers)?

• A. $5$
• B. $7$
• C. $8$
• D. $4$

Answer 1

The correct option is C $8$

• An alkyl group is a structure remaining after one H is removed from an alkane. Corresponding to the molecular formula $C_5{H}_{12}$, three alkanes are possible: n-pentane, iso-pentane, and neo-pentane.
• n-pentane has 3 different types of hydrogen, hence 3 different alkyl groups can be derived from it.
• iso-pentane has 4 different types of hydrogen, hence 4 different alkyl groups can be derived from it.
• neo-pentane has only 1 type of hydrogen, hence 1 alkyl group can be derived from it.

Hence, 8 different five-carbon alkyl groups are possible. Option C is correct.