April 20, 2021, 06:14:10 PM
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Topic: Synthesis of 5-methyl-3-hexen-2-one  (Read 755 times)

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Offline kriggy

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Re: Synthesis of 5-methyl-3-hexen-2-one
« Reply #15 on: February 18, 2021, 11:55:29 AM »
Yes it likely reacts with acetone and then with the aldehyde which is present only in small amounts. I think there is no free pyrrolidine in the reaction or to be more clear: at first it all reacts with the acetone and by the time the aldol reaction happens and pyrrolidine is released, there is no aldehyde to react with it because its added slowly.

Im not sure about the self-aldor reaction with acetone but its going to be slowed compared to the reaction with the aldehyde. I think I saw a ytb video doing this and the reaction took a week at RT to run.

Offline rolnor

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Re: Synthesis of 5-methyl-3-hexen-2-one
« Reply #16 on: February 18, 2021, 12:49:21 PM »
OK, makes sense.

Offline BjornS

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Re: Synthesis of 5-methyl-3-hexen-2-one
« Reply #17 on: February 18, 2021, 01:30:48 PM »
I don't think a self-aldol reaction will occur here. The website below says tertiary enamines can not be coverted into the corresponding imine.

If you add acetone first, I think there would be (mostly) one product because the enamine converted from acetone is tertiary and symmetrical (assymetrical enamines would yield 50:50 both sides to isobutylaldehyde).

In short: I think ~100% (acetone) enamine would be formed because of these reasons.

Website: http://www.chemgapedia.de/vsengine/vlu/vsc/en/ch/12/oc/vlu_organik/keto_enol/aldolkondensation_aehnliche_reaktionen.vlu/Page/vsc/en/ch/12/oc/keto_enol/enamine/enamine.vscml.html

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