Q38E - Organic Chemistry (Mcmurry)

Question

The reaction of cyclohexene with mercury(II) acetate in CH₃OH rather than

H₂O, followed by treatment with NaBH₄, yields cyclohexyl methyl ether rather than cyclohexanol. Suggest a mechanism. 

Step-by-Step Solution

Answer

The mechanism of the reaction is:

Rework, including reaction diagram, also

Mercury(II) acetate ( Hg ( OAC ) 2 )

Its chemical formula is $\mathrm{Hg}({\mathrm{O}}_2{\mathrm{CCH}}_3{)}_2$. It is an organomercury compound. Structure of mercury(II) acetate is

Fig 1

It does reduction reaction. Oxymercuration reaction is done by the reagent mercury(II) acetate. It follows Markovnikov’s rule. 

NaBH 4

It is known as sodium borohydride. Sodium borohydride is used to do reduction reaction usually, it is used to reduce the carbonyl compounds i.e. aldehyde and ketones. Structure of sodium borohydride is:

Fig 2

Mechanism of Reaction

Step 1: Reduction of double bond in the presence of mercury(II) acetate and the removal of OAC to form a cyclic mercurinium ion.

Step 2: Lone pairs of oxygen atom of  ${\mathrm{CH}}_3\mathrm{OH}$ molecule will attack on the carbon atom that is bonded to mercurinium ion and formation of oxygen cation will take place.

Step 3: Nucleophile that has released in first step will abstract the proton.

Step 4: In last step demercuration will take pleace in the presence of reagent sodium borohydride to form the product i.e. Cyclohexyl methyl ether.

Fig