4-Chloro bupropion impurity

4-Chloro bupropion impurity is a synthetic byproduct arising from chlorination at the 4-position of the aromatic ring in bupropion's core structure. It retains the phenylpropanamine backbone with a tertiary amine and a ketone group, but features an additional para-chloro substituent, enhancing steric hindrance and altering electronic properties. This impurity is formed during oxidative chlorination steps in bupropion synthesis, where controlled chlorination introduces the 4-chloro moiety. It serves as a critical HPLC reference standard for quantifying process-related impurities in bupropion APIs.