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

Answer: (a) To prepare 3-Nitrophenol: 1. Diazotize 3-nitroaniline with NaNO2 and HCl. 2. Hydrolyze the diazonium salt with water. (b) To prepare 3-Bromoaniline: 1. Reduce 3-nitroaniline with Sn and HCl. 2. React aniline with Br2 and CH3COOH. (c) To prepare 1,3-Dihydroxybenzene (Resorcinol): 1. Reduce 3-nitroaniline with Sn and HCl. 2. Treat aniline with excess HNO3 and H2SO4. 3. Reduce 1,3-dinitrobenzene with Sn and HCl. 4. Diazotize and hydrolyze 1,3-diaminobenzene with NaNO2 and HCl. (d) To prepare 3-Fluoroaniline: 1. Reduce 3-nitroaniline with Sn and HCl. 2. React aniline with a fluoride source and a copper catalyst. (e) To prepare 3-Fluorophenol: 1. Synthesize 3-fluoroaniline as in part (d). 2. Convert the amino group to a hydroxyl group as in part (a). (f) To prepare 3-Hydroxybenzonitrile: 1. Reduce 3-nitroaniline with Sn and HCl. 2. Diazotize aniline with NaNO2 and HCl. 3. Perform a Sandmeyer reaction with the diazonium salt and CuCN. 4. Introduce a nitro group with HNO3 and H2SO4. 5. Reduce the nitro group with Sn and HCl.

Step-by-step solution

(a) Preparation of 3-Nitrophenol

To convert 3-nitroaniline to 3-nitrophenol, we need to replace the amino group (-NH2) with a hydroxyl group (-OH). The amino group can be diazotized and then converted into the hydroxyl group: 1. Diazotization: Treat 3-nitroaniline with sodium nitrite (NaNO2) and hydrochloric acid (HCl) to form the corresponding diazonium salt (3-nitrobenzenediazonium chloride). 2. Hydrolysis: Treat the diazonium salt with water (H2O) to replace the diazonium group with a hydroxyl group, yielding 3-nitrophenol.

(b) Preparation of 3-Bromoaniline

To convert 3-nitroaniline to 3-bromoaniline, we need to replace the nitro group (-NO2) with a bromo group (-Br). Here are two steps to achieve this: 1. Reduction: Treat 3-nitroaniline with a reducing agent like tin (Sn) and hydrochloric acid (HCl) to reduce the nitro group to an amino group. This will give us aniline. 2. Electrophilic Aromatic Substitution: React aniline with bromine (Br2) and an acid catalyst such as acetic acid (CH3COOH) to introduce a bromo group at the para position, yielding 3-bromoaniline.

(c) Preparation of 1,3-Dihydroxybenzene (Resorcinol)

To prepare resorcinol from 3-nitroaniline, we first transform 3-nitroaniline into a compound that can undergo further substitution reactions to introduce two hydroxyl groups: 1. Reduction: Convert 3-nitroaniline to aniline using tin (Sn) and hydrochloric acid (HCl) as reducing agents. 2. Electrophilic Aromatic Substitution: Treat aniline with an excess of fuming nitric acid (HNO3) in the presence of sulfuric acid (H2SO4) to introduce two nitro groups. This will give us a 1,3-dinitrobenzene. 3. Reduction: Treat 1,3-dinitrobenzene with a reducing agent such as tin (Sn) and HCl to reduce both nitro groups into amino groups. This will give us 1,3-diaminobenzene. 4. Diazotization and Hydrolysis: Treat 1,3-diaminobenzene with NaNO2 and HCl to form the diazonium salts and subsequently hydrolyze them with water (H2O), yielding 1,3-dihydroxybenzene (resorcinol).

(d) Preparation of 3-Fluoroaniline

To synthesize 3-fluoroaniline from 3-nitroaniline, we need to replace the nitro group (-NO2) with a fluoro group (-F): 1. Reduction: Treat 3-nitroaniline with a reducing agent such as tin (Sn) and hydrochloric acid (HCl) to reduce the nitro group to an amino group, forming aniline. 2. Electrophilic Aromatic Substitution: Treat aniline with a fluoride source such as selectfluor in the presence of a suitable solvent and a copper catalyst to introduce a fluoro group, obtaining 3-fluoroaniline.

(e) Preparation of 3-Fluorophenol

To prepare 3-fluorophenol from 3-nitroaniline, follow these steps: 1. Follow steps 1-2 from part (d) to prepare 3-fluoroaniline. 2. Follow steps 1-2 from part (a) to convert the amino group (-NH2) into a hydroxyl group (-OH), yielding 3-fluorophenol.

(f) Preparation of 3-Hydroxybenzonitrile

To synthesize 3-hydroxybenzonitrile from 3-nitroaniline, follow these steps: 1. Reduction: Convert 3-nitroaniline to aniline using tin (Sn) and hydrochloric acid (HCl) as reducing agents. 2. Diazotization: Treat aniline with sodium nitrite (NaNO2) and hydrochloric acid (HCl) to form the corresponding diazonium salt (benzenediazonium chloride). 3. Sandmeyer Reaction: Treat the diazonium salt with copper(I) cyanide (CuCN) to substitute the diazonium group with a cyano group (-CN), yielding benzonitrile. 4. Electrophilic Aromatic Substitution: Treat benzonitrile with a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4) to introduce a nitro group at the 3-position, yielding 3-nitrobenzonitrile. 5. Reduction: Treat 3-nitrobenzonitrile with a reducing agent such as tin (Sn) and hydrochloric acid (HCl) to reduce the nitro group to a hydroxyl group, obtaining 3-hydroxybenzonitrile.