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Topic: mechanism of this reaction  (Read 8116 times)

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HongKongALevelboy

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mechanism of this reaction
« on: October 19, 2004, 03:56:07 AM »
can anyone tell me the mechanism for the conversion of triphenylmathanol to triphenylmethoxymethane , thx !

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Re:mechanism of this reaction
« Reply #1 on: October 19, 2004, 04:34:51 PM »
The mechanism depends on what reagents you use.  The simplest method would be NaH + MeI.  The mechanism involves deprotonation of the alcohol, then SN2 attack of the alkoxide on the methyl iodide.

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Re:mechanism of this reaction
« Reply #2 on: October 19, 2004, 09:00:22 PM »
This doesn't scream carbocation intermediate to you?
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Re:mechanism of this reaction
« Reply #3 on: October 19, 2004, 10:07:45 PM »
Depends how you do it, right?  If you used MeOH/HCl, then it would certainly be an SN1 reaction mechanism, for sure.

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Re:mechanism of this reaction
« Reply #4 on: October 19, 2004, 11:53:35 PM »
Perhaps, but I think this was how they trapped the first carbocations. I'll double check tomorrow, before I stick my foot any deeper.
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HongKongALevelboy

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Re:mechanism of this reaction
« Reply #5 on: October 20, 2004, 07:14:30 AM »
sorry , i add something to my question , the catalyst is HCl , the reaction involves protonation of OH and it s a Sn1 reaction , that s all the question tells me . thx

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Re:mechanism of this reaction
« Reply #6 on: October 20, 2004, 01:12:27 PM »
Okay, under those conditions it's definitely a carbocation intermediate.

I don't see how you could get to a carbocation if you used a base to deprotonate the alcohol though.

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Re:mechanism of this reaction
« Reply #7 on: October 20, 2004, 02:21:01 PM »
I think when he says OH he means protonation of alcohol and not the addition of OH-
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Re:mechanism of this reaction
« Reply #8 on: October 20, 2004, 08:16:57 PM »
Yeah, I think so too.

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Re:mechanism of this reaction
« Reply #9 on: October 22, 2004, 08:02:46 PM »
let @ represent benzene ring

(1) @3C-OH + H+ -> [ @3C-OH2 ]+

(2) [ @3C-OH2 ]+ -> [@3C]+ + H2O

(3) CH3OH + [@3C]+ -> @3C-O-CH3 + H+

The -OH group is protonated by aq HCl in reaction (1)
The protonated triphenylmethanol dissociates to form the carbocation and water in reaction (2).
A lone pair on the oxygen from methanol attacks the carbocation to form a C-O bond, thus cleaving the O-H bond in methanol to regenerate H+, in reaction (3).

This is a SN1 mechanism
« Last Edit: October 22, 2004, 08:07:43 PM by geodome »
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