Question

Question. Give the structures of intermediates A through H in the following synthesis of trans-1-cyclohexyl-2-methoxycyclohexane.

Short answer

Cyclohexanol on reaction with sulphuric acid followed by heating undergoes dehydration, and forms alkene which is product A. Product A undergoes epoxidation and forms product F which on reaction with product E undergoes coupling, and forms product G. Product A on alkoxymercuration-demercuration leads to the formation of product B in which methoxy group is attached.

Product B on reaction with hydrogen bromide followed by heating undergoes elimination and methoxy group acts as a good leaving group, and bromide ion adds to the alkene carbon which forms bromocyclohexane which is product D. Side product formed is methylbromide which is product C.

Formation of products A, B, C, D, E, F and G

Step-by-step solution

Step-1. Formation of products A, B, C, D, E, F, G:

Cyclohexanol on reaction with sulphuric acid followed by heating undergoes dehydration, and forms alkene which is product A. Product A undergoes epoxidation and forms product F which on reaction with product E undergoes coupling, and forms product G. Product A on alkoxymercuration-demercuration leads to the formation of product B in which methoxy group is attached.

Product B on reaction with hydrogen bromide followed by heating undergoes elimination and methoxy group acts as a good leaving group, and bromide ion adds to the alkene carbon which forms bromocyclohexane which is product D. Side product formed is methylbromide which is product C.

Formation of products A, B, C, D, E, F and G

Step-2. Formation of product H:

Product G undergoes reduction reaction with sodium and forms product H in which oxygen of hydroxyl group has negative charge and acts as a good nucleophile and further on reaction with methylbromide, the oxygen anion attacks at methyl and substitution reaction takes place which forms final product.

Formation of product H