ochem problem from topscore test#1

[allstardentist]

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In aldol condensation, in order to remove the OH group from the beta-hydroxyaldehyde, don't we need to add heat? However, according to #76 in topscore #1 test, there's no heat required to remove the OH group and form a C-C double bond.

 

[dat_student]

In aldol condensation, in order to remove the OH group from the beta-hydroxyaldehyde, don't we need to add heat? However, according to #76 in topscore #1 test, there's no heat required to remove the OH group and form a C-C double bond.

my chem books also don't say anything about the heat requirement.

 

[allstardentist]

look at princeton review page 556

 

[dat_student]

look at princeton review page 556

I just did. It may be needed. Apparently some books show it; some don't 🙂

 

[DonExodus]

Aye, all my books show it, including the textbook. It shows the condensation product as C=O and -OH. Once you add heat, you get the C=O and C=C .

If the C=O and -OH product is not listed, and neither is heat, I would just assume the answer is C=O and C=C.

 

[dhollings0]

aldol condensation can be accomplished:
1) Thermally (heat)
2) Acid catalyst
3) Base catalyst

Source:
http://www.organic-chemistry.org/namedreactions/aldol-condensation.shtm

"In some cases, the adducts obtained from the Aldol Addition can easily be converted (in situ) to α,β-unsaturated carbonyl compounds, either thermally or under acidic or basic catalysis."

So I guess heat is not always required. My McMurry textbook discusses condensation using the acid/base catalyst, but does not mention heat; however, Kaplan says heat is required, but does not mention a catalyst.

Hope that helps

 

[DonExodus]

aldol condensation can be accomplished:
1) Thermally (heat)
2) Acid catalyst
3) Base catalyst

Source:
http://www.organic-chemistry.org/namedreactions/aldol-condensation.shtm

"In some cases, the adducts obtained from the Aldol Addition can easily be converted (in situ) to α,β-unsaturated carbonyl compounds, either thermally or under acidic or basic catalysis."

So I guess heat is not always required. My McMurry textbook discusses condensation using the acid/base catalyst, but does not mention heat; however, Kaplan says heat is required, but does not mention a catalyst.

Hope that helps

In the link you provided, it also shows the elimination reaction as needing heat.

 

[allstardentist]

Aye, all my books show it, including the textbook. It shows the condensation product as C=O and -OH. Once you add heat, you get the C=O and C=C .

If the C=O and -OH product is not listed, and neither is heat, I would just assume the answer is C=O and C=C.

The thing is one of the choices was none of the above, so i put that and got it wrong.

 

[DonExodus]

The thing is one of the choices was none of the above, so i put that and got it wrong.

Oh thats just ****ed up...

 

[slayerdeus]

From what I can recall aldol condensation can come about a number of ways. Most notably from Claisen condensation (2 equiv. of ether + strong base -> enolate attacks ether + aq. acid -> aldol) is the one that you should be most familiar with I think.