Chapter 22, Problem 68PP

Interpretation Introduction

Interpretation: The synthetic routes for the given compounds starting from benzene have to be proposed

Concept Introduction:

Electrophilic aromatic substitution: Electrophilic aromatic substitution is a reaction in which the hydrogen atom of an aromatic ring is replaced as a result of an electrophilic attack on the aromatic ring.  Here are three general steps to an electrophilic aromatic substitution.

1. 1) Generation of an electrophile
2. 2) Attack of the electrophile on the aromatic ring, creating a resonance-stabilized carbocation called an arenium ion.   It loses aromaticity in this step, so the energy of activation is high. Furthermore, this is the rate-determining step of the reaction because of the disruption of aromaticity.  The arenium ion is a hybrid resonance structure. There are three general resonance contributors of an arenium ion.
3. 3) Deprotonation of the arenium ion by a weak base to regain aromaticity.

Grignard reaction: The Grignard reaction is an organic reaction used to create a variety of products through the reaction of an organomagnesium compound, also known as a "Grignard reagent" with an electrophile, followed by acid work-up.

Reductive amination: Sodium cyanoborohydride is a strong reducing agent than sodium borohydride.  It reduces the carbonyl group into amine group in a rapid way.  So, it is called as reductive amination reactions.  Aldehyde or ketone group is reacted with primary amine in the presence of sodium cyanoborohydride as a reducing agent and a proton source in the reaction medium to produce secondary amines.

To find: Propose the synthetic routes for the given compound (a) starting from benzene

Apply retrosynthetic analysis

(b)

Interpretation Introduction

Interpretation: The synthetic routes for the given compounds starting from benzene have to be proposed

Concept Introduction:

Electrophilic aromatic substitution: Electrophilic aromatic substitution is a reaction in which the hydrogen atom of an aromatic ring is replaced as a result of an electrophilic attack on the aromatic ring.  Here are three general steps to an electrophilic aromatic substitution.

1. 1) Generation of an electrophile
2. 2) Attack of the electrophile on the aromatic ring, creating a resonance-stabilized carbocation called an arenium ion.   It loses aromaticity in this step, so the energy of activation is high. Furthermore, this is the rate-determining step of the reaction because of the disruption of aromaticity.  The arenium ion is a hybrid resonance structure. There are three general resonance contributors of an arenium ion.
3. 3) Deprotonation of the arenium ion by a weak base to regain aromaticity.

Sandmeyer reaction: 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.

A compound containing an amino group is treated with sodium nitrite and HCl leading to the formation of diazonium salt.

To find: Propose the synthetic routes for the given compound (b) starting from benzene

Apply a retrosynthetic analysis

(c)

Interpretation Introduction

Interpretation: The synthetic routes for the given compounds starting from benzene have to be proposed

Concept Introduction:

Electrophilic aromatic substitution: Electrophilic aromatic substitution is a reaction in which the hydrogen atom of an aromatic ring is replaced as a result of an electrophilic attack on the aromatic ring.  Here are three general steps to an electrophilic aromatic substitution.

1. 1) Generation of an electrophile
2. 2) Attack of the electrophile on the aromatic ring, creating a resonance-stabilized carbocation called an arenium ion.   It loses aromaticity in this step, so the energy of activation is high. Furthermore, this is the rate-determining step of the reaction because of the disruption of aromaticity.  The arenium ion is a hybrid resonance structure. There are three general resonance contributors of an arenium ion.
3. 3) Deprotonation of the arenium ion by a weak base to regain aromaticity.

Grignard reaction: The Grignard reaction is an organic reaction used to create a variety of products through the reaction of an organomagnesium compound, also known as a "Grignard reagent" with an electrophile, followed by acid work-up.

Nucleophilic substitution reaction: It is the reaction of an electron pair donor (the nucleophile, Nu) with an electron pair acceptor (the electrophile).  A sp³-hybridized electrophile must have a leaving group (X) in order for the reaction to take place.  The term S_N2 means that two molecules are involved in the actual transition state.

To find: Propose the synthetic routes for the given compound (c) starting from benzene

Apply a retrosynthetic analysis

(d)

Interpretation Introduction

Interpretation: The synthetic routes for the given compounds starting from benzene have to be proposed

Concept Introduction:

Azo coupling: Aryldiazonium salts on coupling with an activated aromatic ring give an azo dye which produces a deep color in the final product.  This color is due to the extended conjugation in it.  This reaction occurs by electrophilic substitution reaction.  This method is called an azo coupling.  The obtained final compound is known as azo dyes.

Friedel–Crafts acylation: The Friedel–Crafts acylation is the reaction of an arene with acyl chlorides or anhydrides using a strong Lewis acid catalyst. This reaction proceeds via electrophilic aromatic substitution to form monoacylated products.

To find: Propose the synthetic routes for the given compound (d) starting from benzene

Apply a retrosynthetic analysis for the given azo dye