# Which isomer of C_5H_12 will give ONE chloroalkane upon treatment with one equiv chlorine gas?

${H}_{3} C - C {\left(C {H}_{3}\right)}_{3} + {X}_{2} \rightarrow \left(X\right) {H}_{2} C - C {\left(C {H}_{3}\right)}_{3} + H - X$.
All of the methyl groups of neopentane are equivalent, and will give equivalent products on susbtitution. Cyclopentane will likewise give only the 1 substitution product, however, this formula is ${C}_{5} {H}_{10}$ not ${C}_{5} {H}_{12}$.