9701 MCQ Solution 26

Question 26: [Organic > Hydrocarbons]:

Oxidation of an alkene Y gives a diol; further oxidation gives a diketone.

What could be Y?

A CH₃CH=C(CH₃)₂

B (CH₃)₂CHCH=CH₂

C C₆H₅CH=CHC₆H₅

D (C₆H₅)₂C=CHCH₃

Reference: Past Exam Paper – November 2002 Paper 1 Q26

Solution 26:

Answer: C.

To form a diol the alkene would require that the unsaturated carbons each have at least 1 hydrogen atom bonded to it. 

Option A and D do not provide this hence are eliminated. 

In option B the compound has 2 hydrogen atoms bonded to 1 of the unsaturated carbons this will cause it to become partially a primary alcohol and further oxidation will lead to fusion of a ketone from one side and a carboxylic acid on the other not a diketone. Hence option B is also incorrect. 

Option C provides a secondary alcohol on both sides hence will produce a diketone, making it the correct option.