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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: Tonychet2 on May 28, 2012, 08:30:46 pm

Title: why is ethanoic anhydride preffered?
Post by: Tonychet2 on May 28, 2012, 08:30:46 pm

why is ethanoic anhydride preffered instead of ethanoic acid to produce aspirin?

Title: Re: why is ethanoic anhydride preffered?
Post by: iirene on May 28, 2012, 08:43:33 pm

If ethanoic acid was used, then it would create water (ethanoic acid + salicylic acid --> acetylsalicylic acid + water). Therefore, the reaction will also drive backwards (aspirin could undergo hydrolysis and make salicylic acid + ethanoic acid). This means that the reaction will be slow and have a low yield.

Using ethanoic anhydride will increase the yield and reaction rate
ethanoic acid + ethanoic acid --> ethanoic anhydride + water
ethanoic anhydride + salicylic acid --(concentrated H2SO4)--> acetylsalicylic acid + ethanoic acid
then we can use this ethanoic acid to make more ethanoic anhydride! :)

Title: Re: why is ethanoic anhydride preffered?
Post by: Tonychet2 on May 28, 2012, 08:44:41 pm

ahhhhhhh thanks alot... makes total sense