What is the name of \({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{2}}}{\text{CHCOC}}{{\text{H}}_{\text{3}}}\) applying IUPAC rules?

A.     3,3-dimethylpropan-2-one

B.     3-methylbutan-2-one

C.     2-methylbutan-3-one

D.     3-methylbutanal

B

One respondent stated that choices B. 3-methylbutan-2-one and C. 2-methylbutan-3-one would lead to the same structure. However, according to the guide, candidates should be able to apply IUPAC rules to name compounds containing up to six carbon atoms involving a ketone. Hence, applying IUPAC rules, the only answer is in fact B as the compound will be numbered with the lowest number on the ketone. It was surprising that candidates had difficulty naming this compound, and the question proved to be the third most challenging question on the paper, with less than half getting it correct (47.50%). The question had an associated discrimination index of 0.45.