[billsauce]

is an aldehyde bonded to a less substituted carbon more reactive than an aldehyde bonded to more substituted carbon?

1 aldehyde on the structure is bonded to a CH2 group which is bonded to another carbon, while the other aldehyde is bonded to a CH group bonded to 2 other carbons. Which one is more reactive? Or do they both have the same reactivity?

I know aldehydes are more reactive than ketones because they are bonded to 1 carbon. But in this situation, 2 aldehydes are compared. I want to say the aldehyde bonded to the CH2 group is more reactive, but does it not matter since technically they are each bonded to 1 carbon (even though the CH carbon has 2 carbons bonded to it while the CH2 has only 1 carbon bonded to it)?

[billsauce]

heres a picture

[discodermolide]

As far as the Grignard reaction is concerned I don't see much reactivity difference between the two aldehydes.

[billsauce]

it will react with either aldehyde. the question is which one is more likely. aldehydes are pretty reactive

[discodermolide]

As I just said I don't think that either of the aldehydes will be preferred as I don't see a difference between them large enough to enable a differentiation on the basis of reactivity.

[billsauce]

you dont think the extra ch2ch3 group will do anything? i guess thats true since both aldehydes are bonded to 1 carbon

[discodermolide]

As I just said I don't think that either of the aldehydes will be preferred as I don't see a difference between them large enough to enable a differentiation on the basis of reactivity.
Why should the extra CH₂-CH₃ group do anything to the reactivity?

[billsauce]

it might cause a stronger pull on the aldehyde making that carbonyl group less positive?

[OC pro]

Agree with Disco. I would expect a 1:1-mixture. Especially with MeMgBr which is very reactive and small.

[discodermolide]

it might cause a stronger pull on the aldehyde making that carbonyl group less positive?

I don't think that will be significant at all.

[orgopete]

it might cause a stronger pull on the aldehyde making that carbonyl group less positive?

I agree with the poster on this one. The question is not whether the reaction is specific for one carbonyl and no reaction at the other. The question is which carbonyl will react more. Given the large number of molecules, it is virtually impossible to have a 50:50 mixture. One of the isomers must be in greater proportion.

Given that premise, then I also agree with the poster that replacing a H with a CH2CH3 group will increase the electron donation to the carbonyl group and reduce its reactivity, or if one also preferred, increase tge steric hindrance. Granted that the high reactivity of methyl Grignard will also reduce the difference between them, but if greater selectivity were desired, reducing the reaction temperature should slow the reaction and increase selectivity.

[billsauce]

this is why I think the aldehyde bonded to the secondary carbon will react more. The question doesnt give an answer that says it is a 50/50 mixture. There also wouldnt be a CH2CH3 group making the other aldehyde bonded to a tertiary carbon there for no reason.

[sjb]

The only way to be sure is to carry out the experiment, then try to rationalise the answer... Sometimes sterics can say one thing, electronics another...

[billsauce]

i cant carry out the experiment it is just a question on an assignment in class. I know that different R groups on ketones change the reactivity of ketones so wouldnt that effect the aldehyde as well? 1 aldehyde is bonded to a secondary carbon while the other is bonded to a tertiary

[willug]

"The question doesnt give an answer that says it is a 50/50 mixture"

It actually says "none of the above".

"I agree with the poster on this one. The question is not whether the reaction is specific for one carbonyl and no reaction at the other. The question is which carbonyl will react more. Given the large number of molecules, it is virtually impossible to have a 50:50 mixture. One of the isomers must be in greater proportion."

The question in the box was which would be the major product! No doubt there is more of one than the other if you did it on a standard scale say, and could count them all! I mean how many extra molecules (or %) of one isomer do you consider to make something a major product?!