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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: prncess23 on April 23, 2009, 05:49:54 AM

Title: Condensation reactions
Post by: prncess23 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.
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b.
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c.
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d.
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e.
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f.
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thanks.

Title: Re: Condensation reactions
Post by: Dolphinsiu on April 23, 2009, 05:55:14 AM

Please search Aldol condensation in yahoo or google, and then try to work out the answers.

Title: Re: Condensation reactions
Post by: AWK on April 23, 2009, 06:20:26 AM

d. http://en.wikipedia.org/wiki/Claisen_condensation
f. http://en.wikipedia.org/wiki/Dieckmann_condensation

Title: Re: Condensation reactions
Post by: prncess23 on April 24, 2009, 01:14:16 AM

meaning a-c,e are aldol whereas d and f are claisen and dieckmann?

Title: Re: Condensation reactions
Post by: AWK on April 24, 2009, 02:45:48 AM

e is not the aldol condensation (ester + active methylene group)

Read my links

Title: Re: Condensation reactions
Post by: prncess23 on April 24, 2009, 09:00:33 PM

okay so.

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

right?

Title: Re: Condensation reactions
Post by: prncess23 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...

Title: Re: Condensation reactions
Post by: Squirmy 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).

Title: Re: Condensation reactions
Post by: prncess23 on April 25, 2009, 02:17:28 AM

Quote from: prncess23 on April 24, 2009, 09:00:33 PM

okay so.

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

right?

is that correct?

thanks for explaining the alpha carbon.

Title: Re: Condensation reactions
Post by: sjb on April 25, 2009, 04:23:47 AM

Quote from: prncess23 on April 24, 2009, 09:00:33 PM

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

Title: Re: Condensation reactions
Post by: Squirmy 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. ;)

Title: Re: Condensation reactions
Post by: prncess23 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?

Title: Re: Condensation reactions
Post by: sjb on April 29, 2009, 05:40:07 AM

Here's the first step for reaction b. Any ideas now?