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As known benzaldehyde can undergo a cannizaro reaction in which a phenyl group is an electron donating group, so the reaction similar to below (of prop-2-enal) (cannizaro) should occur for similar molecule 'either having all hydrogen connected to SP2 hybridised carbon (eg: pent2,4dienal) or the carbon which is SP3 hybridized connected to double bond should not have any hydrogen connected to it (eg: 4,4,4triimethylbutanaldehyde)' should show cannizaro.

Major product in basic medium should be decided by the below reaction (Cannizaro Reaction) and not aldol condensation. Am I correct?

Cannizaro Reaction

I don't think that acid base reaction can occur with concentrated base in this case.

This may be helpful Bond energy of $\ce{C-H}$ bond in methane $\pu{415 kJ/mole}$.

Bond energy of $\ce{C-H}$ bond in ethene $\pu{444 kJ/mole}$.

Jay
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    Your question isn't about "hydrogens next to sp2 carbons": benzaldehyde has $\ce{C_\mathrm{sp^2}-H}$ bonds as well, but you already know what's going on with benzaldehydes. Your question is really about α,β-unsaturated aldehydes, isn't it? – orthocresol May 04 '21 at 17:10
  • @orthocresol Yes. I have tried to express my thoughts in question as much as I can and I am sorry because I didn't know acrolien will undergo hazardous reaction (and wasted much time of community) and will not represent my doubt clearly. – Jay May 05 '21 at 05:31

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According to The Hazardous Substances Databank entry for acrolein here

An extremely violent polymerization reaction of acrolein results from contact with alkaline materials such as sodium hydroxide, potassium hydroxide, ammonia and amines. Mixing sodium hydroxide and acrolein in a closed container caused the temperature and pressure to increase.

The next compound in the series, crotonaldehyde, certainly also polymerises in alkaline conditions. I am inclined to think this is general. There are just too many other pathways available for these reactive molecules under the strongly basic conditions of Cannizaro, not least retro-aldol.

Waylander
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    I think the retro aldol is the more likely outcome of creating the enolate. You then have pivalaldehyde plus acetaldehyde. Pivaldehyde gives Cannizzaro but acetaldehyde will react all over the place. – Waylander May 05 '21 at 08:08