Sciencemadness Discussion Board

Carbon tetrachloride from tetrachloroethylene and chlorine?

Melgar - 2-2-2018 at 01:59

This reaction seemed very plausible to me, and I can't come up with any reasons that would make it impossible. The idea is, saturate a C2Cl4 solution with Cl2. Presumably there would be a decent amount of C2Cl6 produced, although I imagine the reaction would be reversible to a degree. Keep saturating with Cl2. Now you have an easily-broken C-C bond, and assuming you could get Cl• radicals floating around in the mix, CCl4 would seem to be the most stable product, and thus would eventually dominate the reaction.

A few potential problems:

C2Cl6 might give up Cl2 to form C2Cl4 a bit too easily, or C2Cl6 might not form very readily. But the conversion to C2Cl6 does seem energetically favorable if I remember correctly, and is only reversed at temperatures higher than about 300C or so. If I'm wrong on this, I'm sure I'll be adequately humbled in the responses, but I'm like 95% sure I remember looking this up and confirming it.

The easiest way to produce CCl4 from Cl2 and C2Cl6 might actually be through forming radicals thermally. But the temperatures might be unfavorable for the existence of C2Cl6. (I strongly suspect this is the main impediment.)

If the above is true, it might be possible to generate the needed radicals by adding a catalytic amount of bromine, and then using visible light to generate the radicals. Assuming sufficient quantities of Cl2, any carbon-bromine bonds should be quickly replaced by Cl, no?

All of this is purely theoretical. I have no need or desire for CCl4, but I've seen it mentioned enough recently that I thought I should bring this potential synthesis route up for discussion. Anyone care to either shoot it down or give it a shot?

[Edited on 2/2/18 by Melgar]

halogen - 2-2-2018 at 17:02

C2F6 -> 2 .CF3
2 .CF3 + Xe -> Xe(CF3)2

which is an unstable, waxy solid.

Magpie - 2-2-2018 at 17:15

I have made CCl4 at near 100% yield by sparging Cl2 into CHCl3. The only by-product was a tiny amount of C2Cl6, a white solid. I used a 400w Hg lamp and a borosilicate glass rbf. On a sunny day I think a fair yield could be obtained without the lamp. I posted my procedure on this forum.