Question

Draw a stepwise mechanism for the following reaction.

Short answer

Answer

Step-by-step solution

Stepwise reaction

Stepwise reactions are also termed multiple-step reactions. The bonds are not destroyed and are created simultaneously in a stepwise reaction. So the reaction comprises several intermediates proceeding from the reactants to the products.

Reactions of carbohydrates

Monosaccharides undergo several reactions, and one among them is the hemiacetal reaction. The hemiacetal transforms into an acetal when combined with alcohol and HCl.The acetal formed in the reaction is termed a glycoside.

Stepwise mechanism for the following reaction

The [1] step involves the protonation of the carbonyl compound to generate alcohol. The hydroxyl group is connected to the electron-deficient carbon atom. The reaction can be given as:

Step [1] of the given reaction

In step [2], the electrons found on the OH group of furanose strike the electron-deficient carbon atom of the alcohol. This is followed by step [3], which involves the abstraction of hydrogen ions by water leading to hemiacetal formation. The reactions are given as:

Steps [2] and [3] of the given reaction

Step [4] involves the protonation of the hemiacetal compound and the attack of electrons of the oxygen atom on the carbon atom comprising the water molecule. The elimination of water molecules happens in step [5], creating the oxonium ion. This is followed by step [6], where the abstraction of hydrogen ions leads to acetal formation. The reaction can be given as:

Steps [4], [5], and [6] of the given reaction

Step [7] involves the protonation of the acetal compound. The electrons of the oxygen atom strike the electron-deficient carbon of the alcohol. In step [8], the attack of a water molecule on the oxonium ion leads to the creation of hemiacetal. The reactions can be given as:

Steps [7] and [8] of the given reaction

The protonation of the hemiacetal compound happens in step [9]. The elimination of water occurs in step [10]. The target molecule is acquired when the water molecule strikes the oxonium ion in the last step. The reaction can be given as:

Steps [9] and [10] of the given reaction