Question

Starting with 3-nitroaniline, show how to prepare the following compounds. (a) 3-Nitrophenol (b) 3 -Bromoaniline (c) 1,3 -Dihydroxybenzene (resorcinol) (d) 3-Fluoroaniline (e) 3-Fluorophenol (f) 3 -Hydroxybenzonitrile

Short answer

Question: Prepare the following compounds from 3-nitroaniline: (a) 3-Nitrophenol, (b) 3-Bromoaniline, (c) 1,3-Dihydroxybenzene (resorcinol), (d) 3-Fluoroaniline, (e) 3-Fluorophenol, and (f) 3-Hydroxybenzonitrile. Answer: To synthesize the given compounds from 3-nitroaniline, perform the following reactions: (a) 3-Nitrophenol: Oxidize 3-nitroaniline to 3-nitronitrobenzene, followed by a reduction to 3-nitrophenol. (b) 3-Bromoaniline: Reduce 3-nitroaniline to 3-aminophenol, convert it to 3-bromophenol, and then diazotize it to 3-bromoaniline. (c) Resorcinol (1,3-Dihydroxybenzene): Reduce 3-nitroaniline to 3-aminophenol, diazotize it to 3-nitrosophenol, and hydrolyze it to resorcinol. (d) 3-Fluoroaniline: Reduce 3-nitroaniline to aniline, and then perform an electrophilic substitution with a fluorinating agent. (e) 3-Fluorophenol: Synthesize 3-fluoroaniline from 3-nitroaniline, diazotize it to 3-fluoronitrosobenzene, and hydrolyze it to 3-fluorophenol. (f) 3-Hydroxybenzonitrile: Reduce 3-nitroaniline to 3-aminophenol, perform a Sandmeyer reaction to form 3-hydroxycyanobenzene, and rearrange it to 3-hydroxybenzonitrile.

Step-by-step solution

Oxidation of 3-nitroaniline to 3-nitronitrobenzene

Treat 3-nitroaniline with an oxidizing agent such as potassium permanganate (KMnO4) to convert the amino group to a nitro group, forming 3-nitronitrobenzene.

Reduction of 3-nitronitrobenzene to 3-nitrophenol

Next, perform a reduction reaction using tin (Sn) and hydrochloric acid (HCl) as reducing agents. This will reduce the nitro group to a hydroxyl group, yielding 3-nitrophenol. (b) Preparation of 3-Bromoaniline from 3-nitroaniline

Reduction of 3-nitroaniline to 3-aminophenol

First, reduce the nitro group in 3-nitroaniline to an amino group using Sn and HCl as reducing agents. This yields 3-aminophenol.

Conversion of 3-aminophenol to 3-bromophenol

Next, treat 3-aminophenol with bromine in an aqueous solution to convert the hydroxyl group into a bromine atom, producing 3-bromophenol.

Conversion of 3-bromophenol to 3-bromoaniline

To complete the synthesis, carry out a diazotization reaction by treating 3-bromophenol with sodium nitrite (NaNO2) in dilute HCl at 0-5°C. This will convert the hydroxyl group back into an amino group, yielding 3-bromoaniline. (c) Preparation of 1,3-Dihydroxybenzene (resorcinol) from 3-nitroaniline

Reduction of 3-nitroaniline to 3-aminophenol

Begin by reducing the nitro group of 3-nitroaniline using Sn and HCl as reducing agents. This forms 3-aminophenol.

Diazotization of 3-aminophenol

Next, perform a diazotization reaction by treating 3-aminophenol with NaNO2 in dilute HCl at 0-5°C. This results in the intermediate 3-nitrosophenol.

Hydrolysis of 3-nitrosophenol to resorcinol

Carry out a hydrolysis reaction on 3-nitrosophenol, which can be achieved using a base such as sodium hydroxide (NaOH) in an aqueous solution. This converts the nitroso group into a hydroxyl group, producing 1,3-dihydroxybenzene, also known as resorcinol. (d) Preparation of 3-Fluoroaniline from 3-nitroaniline

Reduction of 3-nitroaniline to aniline

Start by reducing the nitro group in 3-nitroaniline to an amino group using Sn and HCl as reducing agents. This produces aniline.

Electrophilic substitution of aniline with a fluorine atom

Treat aniline with a fluorinating agent such as xenon hexafluoride (XeF6) to carry out an electrophilic substitution reaction, substituting the hydrogen atom in the 3-position with a fluorine atom to yield 3-fluoroaniline. (e) Preparation of 3-Fluorophenol from 3-nitroaniline

Synthesis of 3-fluoroaniline from 3-nitroaniline

Follow the steps provided in part (d) to synthesize 3-fluoroaniline from 3-nitroaniline.

Diazotization of 3-fluoroaniline

Perform a diazotization reaction by treating 3-fluoroaniline with NaNO2 in dilute HCl at 0-5°C. This results in the intermediate 3-fluoronitrosobenzene.

Hydrolysis of 3-fluoronitrosobenzene to 3-fluorophenol

Carry out a hydrolysis reaction on 3-fluoronitrosobenzene, which can be achieved using a base such as NaOH in an aqueous solution. This converts the nitroso group into a hydroxyl group, producing 3-fluorophenol. (f) Preparation of 3-Hydroxybenzonitrile from 3-nitroaniline

Reduction of 3-nitroaniline to 3-aminophenol

First, reduce the nitro group in 3-nitroaniline to an amino group using Sn and HCl as reducing agents. This yields 3-aminophenol.

Sandmeyer reaction to form 3-hydroxycyanobenzene

Treat 3-aminophenol with a mixture of NaNO2 and potassium cyanate (KOCN) and let the solution react at 0-5°C. This results in a Sandmeyer reaction, where the amino group is replaced by a cyano group (CN) and the product 3-hydroxycyanobenzene is formed.

Rearrangement of 3-hydroxycyanobenzene to 3-hydroxybenzonitrile

Heat the product obtained in step 2, 3-hydroxycyanobenzene, causing a rearrangement reaction. The hydroxyl group shifts to the ortho position, resulting in the formation of 3-hydroxybenzonitrile.