Gabriel reaction of 1,3-dibromo-2,2-bis(bromomethyl)propane (1a) gives
2 by displacement of three bromo-substituents by Phthalimide ion and
the fourth by hydroxide, with artifacts 3 and 4 arising from fragmenta
tion and trapping reactions; reaction of 2,2-bis(bromomethyl)propane-1
,3-diol (1b) with phthalimide ion gives mainly phthalimide as well as
minor 'Gabriel' products including 3 and 4.