There is no process to the best of my knowledge where a hydrate anion can be isolated or reacted to form a further product, except in two cases; the
canizzaro reaction of unenolisable aldehydes (dianion formed first), and in the final steps of the haloform reaction, in which case the hydrate anion
kicks out CCl3(-) instead of the usual OH(-) due to the better leaving group ability (lower pKaH). |