Chapter 19.2, Problem 3P

Interpretation Introduction

a)

Interpretation:

Starting from 1-pentanol how pentanal can be prepared is to be shown.

Concept introduction:

Primary alcohols are oxidized to carboxylic acids by strong oxidizing agents like CrO₃ and KMnO₄ etc. The oxidation can be stopped in the aldehyde stage by treating with Dess-Martine periodinate in methylene chloride.

To show:

How to prepare pentanal starting from 1-pentanol.

Interpretation Introduction

b)

Interpretation:

Starting from 1-hexene how pentanal can be prepared is to be shown.

Concept introduction:

When treated with ozone, alkenes form ozonides which when reduced with Zn and acetic acid gets cleaved to yield different carbonyl compounds.

To show:

How to prepare pentanal starting from 1-hexene.

Interpretation Introduction

c)

Interpretation:

Starting from methylpentanoate how pentanal can be prepared is to be shown.

Concept introduction:

Carboxylic acid derivatives like esters can be converted into aldehydes by reduction with diisobutylaluminium hydride (DIBAH) followed by acidification. The reaction is normally carried out at -78°C in toluene solution.

To show:

How to prepare pentanal starting from methylpentanoate.

Interpretation Introduction

d)

Interpretation:

Starting from 1-pentene how pentanal can be prepared is to be shown.

Concept introduction:

Alkenes when subjected to hydroboration-oxidation yield primary alcohols which when oxidized with Dess-Martin periodinate in dichloromethane yield aldehydes.

To show:

How to prepare pentanal starting from 1-pentene.