[alexalexmaiden]

this reaction is used for esterification ... but why do we use DCC DCC is for dehydration...the product is an ester and HCl

[Hunter2]

Check the mechanism

http://www.organic-chemistry.org/namedreactions/steglich-esterification.shtm

[alexalexmaiden]

i dont understand all these mechanisms ... am on the first year in agricultural university of athens ... 

[hypervalent_iodine]

Knowing why we use certain reagents in certain reactions is explained by mechanistic considerations, so your question may be hard for you to answer if you are not able to understand them. Reagents may have multiple uses within synthesis. DCC is used for dehydration reactions, yes, but it is also used to activate carboxylic acids so that they can undergo esterification.

[alexalexmaiden]

thank you , DCC is also used for activating COOH for aminoacids right?

[Babcock_Hall]

DCC can be used to make acids into esters.  DMAP is commonly used as a catalyst.  However, DCC seems redundant if one is starting with an acyl chloride.

[spirochete]

In the most general sense, DCC is used in all these cases to modify the -OH group on the carboxylic acid so that it becomes a better potential leaving group. That is what is uniting all these different mechanisms.

[Altered State]

However, DCC seems redundant if one is starting with an acyl chloride.

This.
I don't see why would you need DCC if you already have an acid chloride and not a carboxilic acid. Maybe for a particular case? Can you post the exact reaction?