Why doesn't isobutyraldehyde undergo aldol condensation when it has an alpha hydrogen
The compound you mentioned does undergo aldol addition, not condensation; I’ll tell you why.
Firstly, the compound only has one alpha hydrogen, which will be extracted by the base during the aldol addition step. After the addition product is formed, there are no hydrogens left for dehydration to occur (write the reaction out with the mechanism, you’ll see). Hence the addition product is formed, but the condensation product is not formed.
As for the Cannizzaro reaction, I assume you're talking about the cross-Cannizzaro reaction with an aldehyde having no alpha hydrogen (like formaldehyde), where the given compound is the limiting reagent. The compound itself cannot undergo Cannizzaro reaction with itself (because it has an alpha hydrogen) but cross-Cannizzaro is surely possible.
The compound you mentioned does undergo aldol addition, not condensation; I’ll tell you why.
Firstly, the compound only has one alpha hydrogen, which will be extracted by the base during the aldol addition step. After the addition product is formed, there are no hydrogens left for dehydration to occur (write the reaction out with the mechanism, you’ll see). Hence the addition product is formed, but the condensation product is not formed.
As for the Cannizzaro reaction, I assume you're talking about the cross-Cannizzaro reaction with an aldehyde having no alpha hydrogen (like formaldehyde), where the given compound is the limiting reagent. The compound itself cannot undergo Cannizzaro reaction with itself (because it has an alpha hydrogen) but cross-Cannizzaro is surely possible.
