Chapter 17, Problem 17.71P

Interpretation Introduction

(a)

Interpretation:

The structure of six-membered cyclic hemiacetal formed by 5-hydroxyhexanal should be drawn.

Concept Introduction:

Hemiacetal is a molecule formed by the addition of an alcohol to an aldehyde or ketone,containing a carbon bonded to one −OH group and one −OR group. For example-

Answer to Problem 17.71P

Explanation of Solution

Reaction of the aldehyde group and the hydroxyl group forms a six-membered cyclic hemiacetal.

Therefore, the structure hemiacetal formed from 5-hydroxyhexanalis as follows:

Interpretation Introduction

(b)

Interpretation:

The number of possible stereoisomers of 5-hydroxyhexanal should be determined.

Concept Introduction:

Stereoisomers are the compounds that are differ only in the spatial arrangements of their atoms. For a molecule with n stereoisomers, a maximum of $2^n$ stereoisomers are possible.

Answer to Problem 17.71P

5-hydroxyhexanal has 2 stereoisomers.

Explanation of Solution

For a molecule with n stereoisomers, a maximum of $2^n$ stereoisomers are possible.

In 5-hydroxyhexanal, there is one stereocenter.

Therefore, number of stereoisomers can be calculated as follows:

$\begin{array}{l}Numb\text{e}rofst\text{e}r\text{e}\text{O}\text{i}s\text{O}m\text{e}rs=2^n\hfill \\ =2^1\hfill \\ =2\hfill \end{array}$

Thus, number of stereoisomers will be 2.

Interpretation Introduction

(c)

Interpretation:

The number of possible stereoisomers of hemiacetal of 5-hydroxyhexanal should be calculated.

Concept Introduction:

Stereoisomers are the compounds that are differ only in the spatial arrangements of their atoms. For a molecule with n stereoisomers, a maximum of $2^n$ stereoisomers are possible.

Answer to Problem 17.71P

Hemiacetal of 5-hydroxyhexanal has 4 stereoisomers.

Explanation of Solution

For a molecule with n stereoisomers, a maximum of $2^n$ stereoisomers are possible.

In hemiacetal of 5-hydroxyhexanal, there are two stereo centres.

Therefore, number of stereoisomers can be calculated as follows:

$\begin{array}{l}Numb\text{e}rofst\text{e}r\text{e}\text{O}\text{i}s\text{O}m\text{e}rs=2^n\hfill \\ =2^2\hfill \\ =4\hfill \end{array}$

Thus, number of stereoisomers are 4.