Sciencemadness Discussion Board

(subsituted) phenol to halobenzene

zaltar - 29-12-2014 at 16:11

Text

Can I make chlorobenzene from phenol with ZnCl2 and anhydrous HCl ? What solvent can be used or do i need
an solvent at all ?

somuch to do, yust thinkin ,fischer she :-)

gdflp - 29-12-2014 at 16:25

I may well be corrected, but I don't think that a Lewis acid and HCl is going to work. This however might be a useful link. This as well, though not very reputable.

[Edited on 12-30-2014 by gdflp]

CuReUS - 4-1-2015 at 09:44

I came across a very interesting article about making aniline from phenol
http://onlinelibrary.wiley.com.sci-hub.org/doi/10.1002/14356...

read page 6

could the same reaction be done,but by replacing ammonia with HCl
but HCl would attack alumina :( ,so some other catalyst has to be found

ParadoxChem126 - 4-1-2015 at 12:12

I do not think the reaction between phenol and HCl/ZnCl2 is viable. This mixture is capable of reacting with alcohols via an SN1 or SN2 mechanism. Phenol is inert to both SN1 and SN2 conditions, thus the reaction cannot occur.

Chlorobenzene can be produced by many other methods, such as the direct chlorination of benzene or the Sandmeyer reaction from aniline.

Maybe this will be useful:
http://www.sciencemadness.org/talk/viewthread.php?tid=8898

macckone - 4-1-2015 at 23:36

Zinc + phenol = benzene (reportedly) then normal chlorination.

DJF90 - 4-1-2015 at 23:54

PCl5

Yugen - 9-1-2015 at 13:24

Quote: Originally posted by zaltar  
Text

Can I make chlorobenzene from phenol with ZnCl2 and anhydrous HCl ? What solvent can be used or do i need
an solvent at all ?

somuch to do, yust thinkin ,fischer she :-)


Nope... and the alternative that does work seems to be a huge waste of time and money. Here's what one book says...
Quote:

Vogel's Practical Chemistry 5th Edition

"Replacement of the hydroxyl group in a phenol by halogen cannot be accomplished by reaction with the hydrogen halides as in the case of alcohols, and reaction with phosphorus halides gives only low yields of halogenobenzenes (except in the case of nitrophenols), the main product being a phosphite or phosphate ester.

ArOH + PCl<sub>3</sub> ---► (ArO)<sub>3</sub>P + 3 HCl

However, if the phenol is first treated with the complex formed from triphenylphosphine and a halogen in acetonitrile solution, an aryloxytriphenylphosphonium halide is formed which on thermal decomposition yields the aryl halide in good yield (e.g. the preparation of p-bromochlorobenzene, Expt 6.30)."


Sounds like a really expensive way to make a aryl halide to me! You might want to try a Hunsdiecker reaction on benzoic acid instead. According to Organic Reaction Volume IX (a differnet book I own), bromobenzene is reported to be synthesized in 46-80% yields with that method. The book says the reaction is really sensitive to temperatures though (meaning you can easily get ortho and para dibromobenzene if you aren't careful).

This is one of the sources that the book cites.

http://pubs.rsc.org/en/content/articlelanding/1950/jr/jr9500...

Also be sure to check out the mercuric oxide variation of this reaction (its supposed to be an easier the variation of the reaction but is too new to be covered by my old book reference).

http://www.orgsyn.org/demo.aspx?prep=cv6p0179

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Edit:
My copy and paste job of Vogel had an error, fixed it.

[Edited on 9-1-2015 by Yugen]