-3
$\begingroup$

I am doing some Aldol reaction in lab,problem is **basically one of my Aldehyde is converting largely in cannizzaro products.**Please suggest me which base I can use so that I will not get cannizzaro products or get them in very less amount.

$\endgroup$

closed as unclear what you're asking by Mithoron, user55119, Jon Custer, Tyberius, Zhe Aug 14 at 18:46

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 3
    $\begingroup$ And what is the reaction, exactly? $\endgroup$ – Raphaël Aug 13 at 18:22
1
$\begingroup$

I suspect that the rogue aldehyde in consideration has highly substituted alpha carbon/s..

Refer https://www.organic-chemistry.org/namedreactions/aldol-addition.shtm for the proper mechanism for aldol addition.

Note that the enolate of the other carbonyl reactant is a nucleophile which adds to the electrophilic carbonyl atom. Naturally, steric hinderance plays a big part in this nucleophilic addition to the aldehyde. Thus, a highly substituted aldehyde shows less tendency towards aldol addition. (Trivia: this same steric interaction is also responsible for the fact that ketones are less reactive towards aldol addition that aldehydes)

Excpetional case: Formaldehye Formaldehyde is the ideal aldehyde for aldol addition (least steric hinderance). But it also has a high tendency to get oxidised to formic acid (Cannizarro product).

Imo, you are carrying out the reaction in a highly basic medium, which will naturally favour cannizzaro in highly substituted aldehydes and formaldehyde. Mildy basic conditions might help.

$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.