Synthesis of 1,1‐dichloro‐2,2‐bis(4‐hydroxyphenyl)‐ethylene via ammonia or methylamine dehydrochlorination. A bisphenol for the preparation of highly flame‐resistant polycarbonates

Ammonia used as both reactant and solvent has been shown to dehydrochlorinate 1,1,1‐tri‐chloro‐2,2‐bis(4‐hydroxyphenyl)ethane smoothly to 1,1‐dichloro‐2,2‐bis(4‐hydroxyphenyl)ethylene. The reaction is complete in 1 hr at 100°C, and after two crystallizations from methanol/water affords polymerizable quality monomer for the synthesis of highly flame‐resistant polycarbonates. The use of organic solvents in combination with ammonia does not offer any rate advantages over pure ammonia. Primary and secondary amines also can be used to effect the dehydrochlorination but, except for the methylamine, are significantly less reactive and lead to less pure product than amonia.