Chemistry Forums for Students > Organic Chemistry Forum

Replacing the -OH group of a primary alcohol with chlorine

(1/2) > >>

tommikas:
Hei everyone!

A new membraan here. Hope you are all doping well.
I have a molecule of a primary alcohol and I would need to replace its -OH group with Cl without using chemicals such as SOCl2, PCl5. I have found several sources saying that it can’t be done using only HCl acid. Other sources say it is possible by heating the solution of the primary alcohol and HCl acid. Would that work and what would be the required temperature and the time of heating? I source that I found said that heating for 2 hours at 120c would work.
Another source that I found said that using a catalyst such as ZnCl2 with HCl acid would work. Would the heating be needed in that case as well? Also I found a source saying that dry ZnCl2 should be used and then HCl gas bubbled into the solution as aqueous HCl would result in poor yealds.
Looking forward to hearing your thoughts and ideas.
Many thanks in advance to everyone who takes the time to reply.

rolnor:
If you heat it should be possible with Lucas reagent but I dont know the yield.
https://en.wikipedia.org/wiki/Lucas%27_reagent

Babcock_Hall:
It might help if we knew the structure of the substrate.

GabrielTojo:
I would not use HCl to transform a primary alcohol into chloride unless the alcohol is very simple. The problem is that very acidic conditions are needed which could destroy the starting material. Conditions need to be particularly acidic when the alcohol is primary (although this has exceptions, such as when the primary alcohol is a benzylic one with an electron-rich aromatic ring)

Therefore, it is preferable to use SOCl2, which is also not the mildest reagent in the world. There are other alternatives in milder conditions.

The problem is that without knowing what the primary starting alcohol is, it is difficult to calibrate the reagents that this alcohol would withstand without decomposing.

Disjointcape:
Chlorinating via HCl is possible but it has to compete vs hydrolysis at those high temperatures. I have done a bromination, doing similar using concentrated HBr with Benzene (toluene should work too) and refluxing with a Dean-Stark trap to help remove any water from the mixture and help prevent the hydrolysis.

Another method would be to the Appel reaction https://www.name-reaction.com/appel-reaction . This reaction and is very mild as all you need is carbon tetrachloride and triphenyl phosphine.

These methods are still not as simple as thionyl chloride or even PCl3, which would be my go to, if I had a choice.

Navigation

[0] Message Index

[#] Next page