Mcat organic chem

[sportsguy131]

What is the major product of the crossed aldol reaction shown below?

The reaction is in the attachemnts....
Can anyone guide me on how to approach this problem....


Thank You

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[PiBond]

-OH is a strong base that is capable of deprotonating alpha hydrogens. Only one of the reactants contains alpha H's in your example.

upon deprotonation, we form our enolate. next, we have an nucleophilic attack by our anionic carbon on the carbonyl of the other reactant. this forms a carbon-carbon bond.

 

[sportsguy131]

hey thx for the quick response. i understand what you meant but how did they come up with the answer d (its in the attachments)

P.S. Sry bad drawings.....

Thank You

 

[PiBond]

hey thx for the quick response. i understand what you meant but how did they come up with the answer d (its in the attachments)

P.S. Sry bad drawings.....

Thank You

when our nucleophile attacks the carbonyl carbon, the pi electrons of the carbonyl kick up and the oxygen becomes protonated to form a secondary alcohol (as a result of the nucleophilic attack on the aldehyde). we call this a beta-hydroxy-aldehyde. we aren't forming a diketone so eliminate B. choice C is incorrect because it doesn't show the alcohol resulting from the nucleophilic addition. Choice A is incorrect since it doesn't correspond to the alpha carbon attacking our carbonyl. once more, choice A shows the nucleophile as a ketone which isn't correct (both reactants are aldehydes). thus, D is the correct answer

hope that helps

 

[orgohacks]

when our nucleophile attacks the carbonyl carbon, the pi electrons of the carbonyl kick up and the oxygen becomes protonated to form a secondary alcohol (as a result of the nucleophilic attack on the aldehyde). we call this a beta-hydroxy-aldehyde. we aren't forming a diketone so eliminate B. choice C is incorrect because it doesn't show the alcohol resulting from the nucleophilic addition. Choice A is incorrect since it doesn't correspond to the alpha carbon attacking our carbonyl. once more, choice A shows the nucleophile as a ketone which isn't correct (both reactants are aldehydes). thus, D is the correct answer

hope that helps

Yes - excellent explanation