Sciencemadness Discussion Board

How fast do benzylic chlorides hydrolyze in cold water?

RareEarth - 5-2-2016 at 12:56

I know the reaction occurs, but I am not sure to what extent.

I'm working on a polymeric macromolcule that has benzylic chloride chains, and I need to wash it with a sodium carbonate solution.

To what extent would a quick wash with this cold solution cause hydrolyzation? I recall a thread months ago somewhere saying that benzyl chloride only hydrolyzes very slowly in water.

Dr.Bob - 5-2-2016 at 17:06

Most of them are stable to short exposure to water. If it is soluable, then make sure to dry the organic layer in MgSO4 or Na2SO4 afterwards. If this a resin, you might want to rinse it with pure water and then acetonitrile afterwards to remove the remaining water.

CuReUS - 6-2-2016 at 05:53

from "war gases" by mario sartoni
"benzyl choride is insoluble in water.......it is fairly stable to water, and only by prolonged boiling with an excess is it decomposed into benzyl alcohol and HCl"

[Edited on 6-2-2016 by CuReUS]

Dr.Bob - 6-2-2016 at 06:50

That is very true, but many substituted benzyl chlorides are more reactive with water, and the bigger problem is if you get a small amount of water into them and then store them, they will react eventually over time. Plus any HCl it generates can ruin reactions if not careful.

If you think about molecular weights, a very small amount of water contains many more moles than a small weight of most benzyl halides, so even a few % of water can decompose a large amount of the benzyl chloride over time. That is one reason that even a small mass of water can ruin some reactions, as most chemicals have a much higher MW, so it takes very little water to be one equivalent to a large molecule.