Chapter 22, Problem 57PP

 (a)

Interpretation Introduction

Interpretation: Major products for the given set of reactions have to be found.

Concept Introduction:

The reagents such as methyl iodide and silver oxide are given and used as the reaction conditions in the given reactions.  This reaction is called Hofmann elimination.  The amines undergo exhaustive alkylation in the presence of excess methyl iodide producing quaternary ammonium salt which is a excellent leaving group.  After treatment with strong base, aqueous silver oxide and heat, quaternary ammonium salt gives alkenes.  Alkene formation involves in E2 elimination.  Through E2 elimination, the major product is less substituted alkene with trace amount of more substituted alkene.

To find: The major product in the reaction (a) via Hofmann elimination

Identify all α- and β-positions in the starting material of the reaction (a)

(b)

Interpretation Introduction

Interpretation: Major products for the given set of reactions have to be found.

Concept Introduction: The general formula for primary amine is −NH₂.  There are several methods available to prepare primary amines.  Among them, Gabriel synthesis plays a very important role for preparing it.  In this method, secondary and tertiary amines are not formed as side products.  It involves in three steps.

Formation of potassium phthalimide (deprotonation)

Potassium phthalimide in alkaline KOH acts as the reagent which has negatively charged phthalimide.  It is formed by the reaction between phthalimide and potassium hydroxide.

Formation of R−N bond by S_N2 nucleophilic substitution

The negative charged nitrogen atom in phthalimide can easily attract the positive side of R−X.  In primary alkyl halides (R−X), R and X get positive and negative charges, respectively when they ionize.  As a result, a bond between nitrogen of phthalimide and carbon of R is formed.  This is S_N2 nucleophilic substitution reaction.  Halogen atom is going away as halide anion.

Formation of primary amine by hydrolysis

The resultant product further goes for hydrolysis using hydrazine as the reagent.  This reaction also follows nucleophilic substitution reaction.  Finally, primary amine is formed with a side product of hydrazine derivative.

To find: Using a Gabriel synthesis, prepare the major product of (b)

Identify the correct alkyl halide involved in the formation of hexylamine

(c)

Interpretation Introduction

Interpretation: Major products for the given set of reactions have to be found.

Concept Introduction:

When sodium cyanide is reacted with alkyl halide, S_N2 nucleophilic reaction of cyanide on alkyl group occurs.  So, cyanide is introduced into alkyl group.  By adding water to alkyl cyanide, cyanide is converted into carboxylic acid group.  When thionyl chloride is added to acid group, the transformation of hydroxyl group into chloride occurs.  If excess ammonia is added to the chloride compound, amide formation is resulted.

To find: Obtain the major product in the reaction (c)

Draw the nucleophilic attack of cyanide on alkyl group

(d)

Interpretation Introduction

Interpretation: Major products for the given set of reactions have to be found.

Concept Introduction:

Sandmeyer reactions use copper salts as the reagents.  Here, aryldiazonium salt is converted into aryl halides or aryl cyanides by using copper halides or copper cyanides.

To find: The major product in the reaction (d) via Sandmeyer reaction

Do nitration of benzene