1 diazonium salt can react with concentrated hydrochloric acid to produce chlorobenzene under the catalysis of cuprous chloride;

2. The reaction temperature is too low and the reaction speed is too slow; If the temperature exceeds 5℃, the generated diazonium salt is easily hydrolyzed into phenols, which reduces the yield. The reaction under weak acid condition can make methyl orange turn sour and precipitate.

Because of the great ortho-steric hindrance of N, N- dimethylaniline, the occurrence of ortho-substitution is limited.