Question

Draw a stepwise mechanism for the conversion of β-D-glucose to both anomers of N-ethyl glucopyranoside, the equation written in Reaction [1].

Short answer

Answer

Mechanism

Step-by-step solution

β-D-glucose

In theβ-D-glucose, the configuration at C-1 and C-5 carbons are trans to each other. This compound reacts with an amine under mildly acidic conditions forms a carbocation intermediate.

Carbocation

The hydroxyl group reacts with the proton and forms${\mathrm{H}}_2{\mathrm{O}}^{+}$ ; after losing this${\mathrm{H}}_2{\mathrm{O}}^{+}$ during the reaction, a carbocation intermediate is formed.

The shape of the carbocation is planar, and the nucleophile can attack it both above and below the plane and forms alpha and beta-N-ethyl glycopyranoside.

Mechanism

The mechanism involves the formation of a carbocation in step 1 and the attack of the nucleophile on the carbocation in step 2.

Stepwise mechanism