ORGLIST: allene hydration

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From: Alison og Thomas Høyer (alihoyer$##$mobilixnet.dk)
Date: Wed Sep 06 2000 - 13:31:41 EDT

It is a good question.
I think, it goes like this:

1) Formation of the stable allyl carbo-cation (like you suggest)
2) Hydration of the second double bond via stable cation to give propylene glycol.
3) Elimination of water via stable cation to 2-Hydroxypropene
4) tautomerisation to give acetone.

Thomas Høyer

----- Oprindelig meddelelse -----
Fra: Witek Mozga <mozgaw$##$rocketmail.com>
Til: Multiple recipients of list orglist <orglist$##$dq.fct.unl.pt>
Sendt: 6. september 2000 18:15
Emne: ORGLIST: allene hydration

> Hello everybody,
>
> I have just read in a book that allene undergoes hydration to give
> acetone:
> H+
> CH2=C=CH2 + H2O -> CH3-CO-CH3
> (To see correctly use courier font)
>
> But this means that when protonated, allene forms the less stable
> cation:
>
> H+ +
> CH2=C=CH2 -> CH2=C-CH3 -> CH3-CO-CH3
>
>
> instead of the more stable allilic one:
>
> +
> CH2=C=CH2 -X-> CH2-CH=CH2
>
> Does anybody know why is this so? Or maybe
> there is an error in the book?
>
> With kindest regards,
>
> Witek Mozga
>
> mozgaw$##$rocketmail.com
> mozga$##$trimen.pl
> http://www.trimen.pl
>
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