Which of the following is not a isomer of pentane?

• A

  $n$ -pentane
• B

  2,2-dimethyl 1-propane
• Correct answer
  C

  2,3-dimethyl 1-butane
• D

  2-methyl 1-butane

Solution

$n$ -pentane $\begin{array}{lll}\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3} & \left(\mathrm{C}_{5} \mathrm{H}_{12}\right)\end{array}$ (b) 2,2-dimethyl-1-propane
(c) 2,3-dimethyl-1-butane
(d) 2-methyl-1-butane

Hence, the correct answer is option: 'C'.