Chemistry 9701 · AS & A Level · Organic synthesis

Organic synthesis — practice question

Carvone is found in spearmint, and one stereoisomer of carvone is found in caraway seeds. If either isomer is treated with hydrogen in the presence of a nickel catalyst, a mixture of isomers with structural formula X is produced.
(a(i))[1]

State the type of stereoisomerism that carvone is able to show. Explain your answers.

(a(ii))[2]

Write an equation, using molecular formulae, to represent this conversion of carvone into X.

(b)

X can be made from methylbenzene by the route shown. Identify the reagents and conditions needed for steps 1 to 6.

(b(i))[1]

Name the mechanism for step 1.

(b(ii))[2]

What type of reaction occurs in each of the following steps? step 3 step 5

(b(iii))[6]

Suggest the reagents and conditions for each of the steps below. step 1 step 2 step 3 step 4

(c(i))[1]

In step 6, hydrogen adds to the benzene ring to give the cyclohexane ring in $X$. The six hydrogen atoms are all introduced onto the same side of the benzene ring. State the reagents and conditions required for this reaction.

(c(ii))[2]

Complete the part structure so that it shows the isomer of $X$ most likely to be obtained in this reaction.

Worked solution & mark scheme

This 15-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Optical, because a chiral carbon is bonded to 4 different groups” …

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