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Topic: Condensation reactions  (Read 5470 times)

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Offline prncess23

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Condensation reactions
« on: April 23, 2009, 05:49:54 AM »
please help me.
i dont even know how to do any of these...much less even where to being.

Give the products of the following condensations:
a.


b.


c.


d.


e.


f.



thanks.

Offline Dolphinsiu

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Re: Condensation reactions
« Reply #1 on: April 23, 2009, 05:55:14 AM »
Please search Aldol condensation in yahoo or google, and then try to work out the answers.

Offline AWK

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Offline prncess23

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Re: Condensation reactions
« Reply #3 on: April 24, 2009, 01:14:16 AM »
meaning a-c,e are aldol whereas d and f are claisen and dieckmann?

Offline AWK

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Re: Condensation reactions
« Reply #4 on: April 24, 2009, 02:45:48 AM »
e is not the aldol condensation (ester + active methylene group)

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Offline prncess23

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Re: Condensation reactions
« Reply #5 on: April 24, 2009, 09:00:33 PM »
okay so.

a. claisen
b. henry
c. henry
d. claisen
e. claisen
f. dieckman

right?

Offline prncess23

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Re: Condensation reactions
« Reply #6 on: April 24, 2009, 09:09:13 PM »
oh yea.. so for example in a...what are alpha carbons...im having a hard time determining them...

Offline Squirmy

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Re: Condensation reactions
« Reply #7 on: April 24, 2009, 10:58:59 PM »
For carbonyl compounds, alpha carbons are the ones directly attached to the carbonyl (C=O) carbon. It goes on beta, gamma, delta...omega.

so for 2-pentanone, you have:

CH3-CO-CH2-CH2-CH3
 a             a      b      g

(a=alpha, b=beta, g=gamma).

Offline prncess23

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Re: Condensation reactions
« Reply #8 on: April 25, 2009, 02:17:28 AM »
okay so.

a. claisen
b. henry
c. henry
d. claisen
e. claisen
f. dieckman

right?

is that correct?

thanks for explaining the alpha carbon.

Offline sjb

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Re: Condensation reactions
« Reply #9 on: April 25, 2009, 04:23:47 AM »
okay so.

a. claisen
b. henry
c. henry
d. claisen
e. claisen
f. dieckman

right?

I'd class a as a classical aldol, not sure about b , but the others seem fine. They're all variations on a theme though, don't necessarily get hung up on names, just concentrate on the essentials of the reaction

Offline Squirmy

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Re: Condensation reactions
« Reply #10 on: April 25, 2009, 02:10:48 PM »
B is correct as a Henry reaction.  C isn't, though, because there's no nitro compound.

With the alpha carbon of a nitrile acting as the nucleophile, I'd consider B a Knoevenagel condensation, which is a more general class...B & C are both Knoevenagel condensations, but only B is also a Henry. Perhaps there is also a special name when a nitrile is used, but I'm not familiar with one.

I like named reactions...they're very useful and convenient. When someone says they used the Huang-Minlon modification of the Wolff-Kishner reaction, I get a very good idea of what they did.

That said, I hope you also recognize the similarities between the reactions in your list. Try not to lose sight of the forest for the trees. ;)

Offline prncess23

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Re: Condensation reactions
« Reply #11 on: April 29, 2009, 04:58:27 AM »
this is driving me nuts. i got the answers to a few of them but none of the henry reactions.

what did u guys get?

Offline sjb

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Re: Condensation reactions
« Reply #12 on: April 29, 2009, 05:40:07 AM »
Here's the first step for reaction b. Any ideas now?

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