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Author: Subject: ACID-CATALYZED ESTER FORMATION
ANDLOS
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[*] posted on 18-12-2009 at 12:10
ACID-CATALYZED ESTER FORMATION


I want to ask about the ideal method for ester formation from benzoic acid

the problem that I use abolute ethanol and sulfuric acid and make reflux for 7 hr but only small amount of acid converted to ester i leave reaction for secod day crystals formed perhaps it is of ester

i do not know whether to continue reflux or make separation between acid and ester and how i will make such separation and how to deal with acid after that
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bbartlog
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[*] posted on 18-12-2009 at 12:38


Ethyl benzoate ester is liquid at room temperature. Whatever your crystals are, they aren't the ester you're after. BTW, how do you know that only a small amount of acid was converted to the ester?
More generally, it would be nice to know things like the temperature you tried to do this at, the concentration of your sulfuric acid, and the amounts of the reagents.
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[*] posted on 18-12-2009 at 12:43


What were your proportions? I usually use about 5g of carboxylic acid, 50ml of alcohol and 6ml of sulfuric acid, plus a few boiling stones and a water cooled reflux cndesor. Then I just let it reflux occasionally adding ice cubes to keep the water cool. For Fischer esterfication I find near 100% conversion in 4 hours.



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ANDLOS
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[*] posted on 18-12-2009 at 12:43


Sorry dr BTW---what does it mean

I use 1ml conc sulfuric acid and 24 ml absolute ethanol for esterificaiton of 4 gm of 4-chloro-3-nitro benzoic acid
but i want to ask can i use methanol and is it nessecary to be absolute thanks alot
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[*] posted on 18-12-2009 at 15:22


It means By The Way(BTW).

What do you mean can you use MeOH? If thats the Ester you want then you can. You do understand how this reaction takes place don't you? The mechanics of the reaction are fairly simple.





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medchem
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[*] posted on 18-12-2009 at 21:45


@andlos, electron-withdrawing groups, like nitro group, on the aromatic ring of benzoic acid hinder esterification. May be because of that you are getting low yield while putting for short time. (though for nonsubstituted it will be completed within few hr). So its better you put more time.
You can get precipitate on cooling which can be separated by filtration.
Reference below has done the esterification of the compound you have mentioned. Please refer the following article.

http://pubs.acs.org/doi/abs/10.1021/cc0499486 (for method)

http://www2.heidelberg.edu/depts/chm/fischer.html (good for general understanding)




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Nicodem
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[*] posted on 19-12-2009 at 05:42


ANDLOS, please learn to UTFSE. There are some examples of methyl and ethyl benzoate synthesis on this forum, as well as many more in the literature. Fischer esterification in general is often discussed here.
Also, you seem to have not even bothered to read anything about what you are doing. Such an attitude can be dangerous when what you are doing is chemistry related. At least read the Esterification chapter in Kirk-Othmer. That is a good review on the subject for a beginner.
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ANDLOS
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[*] posted on 19-12-2009 at 07:23


Quote: Originally posted by Nicodem  
ANDLOS, please learn to UTFSE. There are some examples of methyl and ethyl benzoate synthesis on this forum, as well as many more in the literature. Fischer esterification in general is often discussed here.
Also, you seem to have not even bothered to read anything about what you are doing. Such an attitude can be dangerous when what you are doing is chemistry related. At least read the Esterification chapter in Kirk-Othmer. That is a good review on the subject for a beginner.


why dr you say that i didnot read thing i read too much but i am realy beginnter and try to learn ,
hope not to bother you

and realy i need help from you and all member

sorry dr what is meant by UTFSE
thanks dr
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ANDLOS
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[*] posted on 19-12-2009 at 07:24


Quote: Originally posted by crazyboy  
What were your proportions? I usually use about 5g of carboxylic acid, 50ml of alcohol and 6ml of sulfuric acid, plus a few boiling stones and a water cooled reflux cndesor. Then I just let it reflux occasionally adding ice cubes to keep the water cool. For Fischer esterfication I find near 100% conversion in 4 hours.


thanks alot dr
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medchem
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[*] posted on 19-12-2009 at 08:33


this shows you are not a search engine-philic. Just type the word in google, bing or yahoo search engine, you will get the meaning.;)



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ANDLOS
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[*] posted on 19-12-2009 at 09:01


Quote: Originally posted by medchem  
this shows you are not a search engine-philic. Just type the word in google, bing or yahoo search engine, you will get the meaning.;)


UTFSE = using the freeking search engine

is that right:D
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ANDLOS
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[*] posted on 19-12-2009 at 09:10


Quote: Originally posted by Nicodem  
ANDLOS, please learn to UTFSE. There are some examples of methyl and ethyl benzoate synthesis on this forum, as well as many more in the literature. Fischer esterification in general is often discussed here.
Also, you seem to have not even bothered to read anything about what you are doing. Such an attitude can be dangerous when what you are doing is chemistry related. At least read the Esterification chapter in Kirk-Othmer. That is a good review on the subject for a beginner.


please dr I try to search Esterification chapter Kirk-Othmer

but i dont have access to wiley if you can help me and give me this chapter certainley

realy thanks alot
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hissingnoise
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[*] posted on 19-12-2009 at 09:14


Just to be clear---it means Use the Forum (Fucking) Search Engine.
'Freaking' or 'freeking' is for wimin when they're shoppin'. . .




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Nicodem
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[*] posted on 19-12-2009 at 15:42


Quote: Originally posted by ANDLOS  

please dr I try to search Esterification chapter Kirk-Othmer

but i dont have access to wiley if you can help me and give me this chapter certainley

I thought you said you read too much?

Attachment: Esterification & Esters (Kirk-Othmer).pdf (767kB)
This file has been downloaded 11069 times

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ANDLOS
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[*] posted on 20-12-2009 at 10:57


Quote: Originally posted by Nicodem  
Quote: Originally posted by ANDLOS  

please dr I try to search Esterification chapter Kirk-Othmer

but i dont have access to wiley if you can help me and give me this chapter certainley

I thought you said you read too much?

Realy I am so thankful to you
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[*] posted on 20-12-2009 at 13:57


This might work if you substituted benzoic acid for acetic acid. Click to enlarge picture.

http://www.sciencemadness.org/talk/viewthread.php?tid=11828#...
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