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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: measaint on July 22, 2009, 10:47:50 AM

Title: Acid base wash
Post by: measaint on July 22, 2009, 10:47:50 AM

Why do we wash a product with acid and base afetr sythesis? What chemical recation ensues when do so ?

Thank in advance
Saint

Title: Acid base wash
Post by: measaint on July 22, 2009, 10:49:47 AM

Sorry just rewriting, had a lot of spelling mistakes :)


Why do we wash a product with acid and base after sythesis? What chemical reaction ensues when we do so ?

Thanks in advance
Saint

Title: Re: Acid base wash
Post by: Dan on July 22, 2009, 01:08:50 PM

It depends on what is in the reaction mixture. Generally, washing with acid will protonate any bases and the resulting salt will be more soluble in water (relative to organic layer), on the other hand washing with base will deprotonate any acids, forming salts, which again are more water soluble (relative to organic layer).

So for example, if you have pyridine in your organic layer you can wash with dilute HCl to remove it as the more water soluble pyridinium chloride. If you had acetic acid in your organic layer you could wash with saturated sodium bicarbonate to remove it as the more water soluble sodium acetate.

If your product is an organic acid though, you probably wouldn't want to wash that with base, likewise if your product was, for example, an amine you probably wouldn't want to wash it with acid as you may pull it into the aqueous layer.

Title: Re: Acid base wash
Post by: Captain Sci on July 22, 2009, 01:34:14 PM

After completing the acid and/or base extraction cycles, it is always worth washing your mixture with saturated sodium chloride (i.e. salt) solution. The salt solution will remove any aqueous acid or base droplets and water-soluble salts that you were unable to remove previously.

Title: Acid base wash
Post by: measaint on July 22, 2009, 01:38:58 PM

Thanks a bunch for the reply . Now I have a clearer idea of what I am doing. ;D

Title: Re: Acid base wash
Post by: popo2801 on November 24, 2009, 09:16:48 AM

SO if you want to remove a carboxilic acid from your organic phase you should do a base wash?

Title: Re: Acid base wash
Post by: Dan on November 24, 2009, 01:06:34 PM

Quote from: Dan on July 22, 2009, 01:08:50 PM

If you had acetic acid in your organic layer you could wash with saturated sodium bicarbonate to remove it as the more water soluble sodium acetate.

Title: Re: Acid base wash
Post by: kiranglobal on February 19, 2010, 04:29:37 AM

It depends on wat acid you use . :P