Experiment # 8 Six-Step Synthesis Aniline to 1-Bromo-3cholor-5iodobenzene

Experiment # 8

Six-Step Synthesis

Aniline to 1-bromo-3cholor-5iodobenzene

Cristian M. Dobre

Chemistry 245 Laboratory University of Pennsylvania, Philadelphia, PA 19104

Spring 2001

Abstract

In this multi-step synthesis I prepared 1-bromo-3-chloro-5-iodobenzene from a starting sample of aniline. The complete reaction consisted of eight steps that were completed during a total of five laboratory periods. During the first period I completed the acetylation and bromination to form 4-bromoacetanilide. The second period I performed a chlorination to produce 4-bromo-2chloroacetanilide. During the third period I hydrolyzed the amide to form 4-bromo-2chloroaniline. I iodinated this product to form 4-bromo-2-chloro-6-iodoaniline during the fourth period. The last period consisted of a deamination reaction to produce the final product 1-bromo-3-chloro-5-iodobenzene. The complete synthesis scheme is included below. The normal yield from each individual step is on the order of 60 to 90%. I was able to maintain this level of yield for all steps (>60%), except the last one, where an average yield was ~ 40 % (my result was ? %).

Synthesis Scheme!

Introduction

Most of the reactions involved an electrophilic aromatic substitution. There are some very important features in this experiment that is commonly used in aromatic chemistry. The first is the protection of an amino group from possible electrophilic substitutions reactions by its conversion to an amide, and soon after regeneration back to the original amino group. The second is the introduction and removal of an amino group because of its directing and activating capabilities during the substitutions. I started with a prepared sample (3.7 g) of aniline.

- Part I Preparation of 4-bromoacetanilide (Acetylation and Bromination)

The chemical structure of aniline 1 is shown below. This compound belongs to the family of benzenes with an attached...