Question

Consider the following reaction:

‘$\mathrm{X}$’, '$\mathrm{Y}$‘ and ’$\mathrm{Z}$' in these reactions are respectively.

• A. $4,5\&5$
• B. $5,4\&5$
• C. $5,6\&5$
• D. $4,6\&5$

Answer 1

The correct option is D

$4,6\&5$

Explanation for correct option:

(D)

First, let us understand the given reactions of glucose.

The first reaction:

Glucose $+\mathrm{ROH}\underset{}{\overset{\mathrm{dry}\mathrm{HCl}}{\to }}$Acetal $\underset{{\left({\mathrm{CH}}_3\mathrm{CO}\right)}_2\mathrm{O}}{\overset{{\mathrm{x}}_{\mathrm{eq}.}\mathrm{of}}{\to }}$acetyl derivative

• In this reaction, glucose reacts with alcohol $\left(\mathrm{ROH}\right)$ in presence of dry $\mathrm{HCl}$ to form $\mathrm{\alpha }$ or $\mathrm{\beta }$ alkyl glycosides or acetal, which are cyclic anomeric forms of glucose.
• Then, the glycosides react with ${\mathrm{X}}_{\mathrm{eq}}$ of ${\left({\mathrm{CH}}_3\mathrm{CO}\right)}_2\mathrm{O}$ to form an acetyl derivative.
• Now, the acetyl group of ${\left({\mathrm{CH}}_3\mathrm{CO}\right)}_2\mathrm{O}$ replace $\mathrm{OH}$ group present in acetal compound to form acetyl derivative.
• The acetal compound of glucose have $4$ $\mathrm{OH}$ groups that are replaced by acetyl group so the value of ${\mathrm{X}}_{\mathrm{eq}}$ is $4$.

The second reaction:

Glucose $\underset{}{\overset{\mathrm{Ni}/{\mathrm{H}}_2}{\to }}$A $\underset{{\left(C{H}_{3}CO\right)}_{2}O}{\overset{{\mathrm{y}}_{\mathrm{eq}.}\mathrm{of}}{\to }}$ acetyl derivative

• In this reaction, the glucose molecule undergoes hydrogenation due to which the double present in glucose break and gets bonded with hydrogen so product A is hexamethanol.
• Now, the acetyl group of ${\left({\mathrm{CH}}_3\mathrm{CO}\right)}_2\mathrm{O}$ replace $\mathrm{OH}$ group present in hexamethanol to form an acetyl derivative.
• Hexamethanol has $6$ $\mathrm{OH}$ groups that are replaced by acetyl group so the value of ${\mathrm{Y}}_{\mathrm{eq}.}$ is $6$.

The third reaction:

Glucose $\underset{{\left({\mathrm{CH}}_2\mathrm{CO}\right)}_2\mathrm{O}}{\overset{{\mathrm{z}}_{\mathrm{eq}}\mathrm{of}}{\to }}$acetyl derivative

• In this reaction, glucose directly reacts with ${\left({\mathrm{CH}}_3\mathrm{CO}\right)}_2\mathrm{O}$ and $\mathrm{OH}$ group present in glucose is replaced by an acetyl group to form an acetyl derivative.
• Glucose have $5$ $\mathrm{OH}$ groups that are replaced by acetyl group so the value of ${\mathrm{Z}}_{\mathrm{eq}}$ is $5$.
• Therefore, the ‘$\mathrm{X}$’, '$\mathrm{Y}$‘ and ’$\mathrm{Z}$' for glucose reactions are $4,6\&5$

Hence, option D is correct.