Chapter 13, Problem 13.81QP

(a)

Interpretation Introduction

Interpretation:

The structure of hemiacetal obtained from the addition reaction of $\text{2-pentanone}$ with ethanol has to be drawn.

Concept Introduction:

Addition reaction of one molecule of alcohol with an aldehyde or ketone gives a hemiacetal.

Hemiacetal is characterized by a carbon, which is bonded to one hydroxyl group $\left(\text{-OH}\right)$ and one alkoxy group $\left(\text{-OR}\right)\text{.}$

Hemiacetals are unstable.  In the presence of acid and excess alcohol, they undergo a substitution reaction in which the $\text{-OH}$ group of the hemiacetal is exchange for another $\text{-OR}$ group from the alcohol.  The product formed is called as acetal.  A carbon bonded to two alkoxy groups $\left(\text{-OR}\right)$ is the called as acetal.

A general reaction representing the addition of one alcohol molecule to an aldehyde or a ketone is,

(b)

Interpretation Introduction

Interpretation:

The structure of hemiacetal obtained from the addition reaction of acetophenone with ethanol has to be drawn.

Concept Introduction:

Refer to part (a).

(c)

Interpretation Introduction

Interpretation:

The structure of hemiacetal obtained from the addition reaction of cyclopentanone with ethanol has to be drawn.

Concept Introduction:

Refer to part (a).