The given observations are to be explained by the halogenation mechanism. Concept Introduction: ▸ Keto and enol form of carbonyl compounds are constitutional isomers. Inter-convertible keto and enol forms are tautomer. ▸ An enol and enolates can be formed by replacing the hydrogen at the α carbon. ▸ The α hydrogen can undergo halogen substitution at the α carbon in the presence of an acid and a base. ▸ When halogen substitution reaction takes place in the presence of an acid it is called as acid catalyzed halogenation reaction. ▸ When halogen substitution reaction takes place in the presence of a base it is called as base prompted halogenation reaction. ▸ In the base prompted halogenation reaction and acid catalyzed halogenation reaction slows rates are independent from the concentration of the halogens. ▸ The equimolar mixture of two enantiomers are called a racemic mixture. ▸ Racemization takes place at α hydrogen in the presence of acids or bases.

Question

Predict the major products of the following reactions, including stereochemistry where appropriate. (a) potassium tert-butoxide + methyl iodide (b) sodium methoxide + tert-butyl iodide

Answer 1

Question

Chapter 18, Problem 5PP

Interpretation Introduction

Interpretation:

The given observations are to be explained by the halogenation mechanism.

Concept Introduction:

▸ Keto and enol form of carbonyl compounds are constitutional isomers. Inter-convertible keto and enol forms are tautomer.

▸ An enol and enolates can be formed by replacing the hydrogen at the α carbon.

▸ The α hydrogen can undergo halogen substitution at the α carbon in the presence of an acid and a base.

▸ When halogen substitution reaction takes place in the presence of an acid it is called as acid catalyzed halogenation reaction.

▸ When halogen substitution reaction takes place in the presence of a base it is called as base prompted halogenation reaction.

▸ In the base prompted halogenation reaction and acid catalyzed halogenation reaction slows rates are independent from the concentration of the halogens.

▸ The equimolar mixture of two enantiomers are called a racemic mixture.

▸ Racemization takes place at α hydrogen in the presence of acids or bases.

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