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Topic: mechanism of riemann tiemann reaction  (Read 4445 times)

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Offline lijo

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mechanism of riemann tiemann reaction
« 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) ??

Offline discodermolide

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Re: mechanism of riemann tiemann reaction
« Reply #1 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
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Offline lijo

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Re: mechanism of riemann tiemann reaction
« Reply #2 on: April 05, 2012, 05:30:47 AM »
but i want to know whether it is called hydrolysis or nucleophillic substitution?? ???

Offline discodermolide

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Re: mechanism of riemann tiemann reaction
« Reply #3 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!
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Offline sjb

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Re: mechanism of riemann tiemann reaction
« Reply #4 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.

Offline discodermolide

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Re: mechanism of riemann tiemann reaction
« Reply #5 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?
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Offline Dan

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Re: mechanism of riemann tiemann reaction
« Reply #6 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).

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