Chemical Forums

Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: lijo on April 04, 2012, 11:28:50 PM

Title: mechanism of riemann tiemann reaction
Post by: lijo on April 04, 2012, 11:28:50 PM
hi all,
        After the attack of CCl2 on phenol the attack of OH- on CCl2 is called hydrolysis or SN1 (NUCLEOPHILLIC SUBSTITUTION) ??
Title: Re: mechanism of riemann tiemann reaction
Post by: discodermolide on April 05, 2012, 03:36:19 AM
hi all,
        After the attack of CCl2 on phenol the attack of OH- on CCl2 is called hydrolysis or SN1 (NUCLEOPHILLIC SUBSTITUTION) ??


Have a look at this link:
http://en.wikipedia.org/wiki/Reimer–Tiemann_reaction
Title: Re: mechanism of riemann tiemann reaction
Post by: lijo on April 05, 2012, 05:30:47 AM
but i want to know whether it is called hydrolysis or nucleophillic substitution?? ???
Title: Re: mechanism of riemann tiemann reaction
Post by: discodermolide on April 05, 2012, 06:53:15 AM
but i want to know whether it is called hydrolysis or nucleophillic substitution?? ???

It's a hydrolysis.
Sorry for not pasting in the almost correct link!
Title: Re: mechanism of riemann tiemann reaction
Post by: sjb on April 05, 2012, 07:08:46 AM
but i want to know whether it is called hydrolysis or nucleophillic substitution?? ???

It's a hydrolysis.
Sorry for not pasting in the almost correct link!


You can probably call it either, depending on what you want to highlight.
Title: Re: mechanism of riemann tiemann reaction
Post by: discodermolide on April 05, 2012, 08:43:01 AM
but i want to know whether it is called hydrolysis or nucleophillic substitution?? ???

It's a hydrolysis.
Sorry for not pasting in the almost correct link!


You can probably call it either, depending on what you want to highlight.


With the (OH)-Ar-CCl2 group you are at the aldehyde oxidation level. With, I assume, aqueous OH- this would be a hydrolysis akin to an acetal?
Title: Re: mechanism of riemann tiemann reaction
Post by: Dan on April 05, 2012, 05:23:56 PM
It is a hydrolysis that proceeds by a nucleophilic substitution of chloride by hydroxide followed by elimination of HCl.

The substitution step is loss of chloride from 2-dichloromethylphenoxide, followed by addition of hydroxide. This is, as far as I can see, an SN1 reaction, the product of which eliminates HCl spontaneously.

SN1 and hydrolysis are not mutually exclusive terms. Hydrolysis is a term referring to the overall result of the reaction - a comparison of input to output - while SN1 is descriptive of the mechanism - how the output is generated from the input.

I would say it is a hydrolysis reaction that involves an SN1 substitution step (in addition to an elimination step).