carboxylic acid react with p2o5
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P2O5 acts as a dehydrating agent, and results in formation of acid anhydride of carboxylic acid. For instance if we take formic acid, HC(O) OH, it forms HC(O) - O - C(O)H, where the O in brackets is Double bonded.
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hi frnd
here is ur answer Here is a mechanism for the dehydration of an acid to an anhydride using phosphorus pentoxide.
The OHOH group is not a very good leaving group. Even in simpler reactions like the dehydration of an alcohol to an olefin we often first convert the hydroxyl group into a better leaving group by protonation with acid or conversion to an inorganic ester (for example using thionyl chloride or phosphorus pentoxide). The same thing takes place here - we are converting the acid's hydroxyl group into a better leaving group.
Why is HPO3HPOX3 such a good leaving group? Look at all the resonance structures you can draw for the anion PO3−POX3X−. It's stability makes the reaction exothermic and strongly drives the dehydration process to the product side.
For completeness, here is a link to a drawing and discussion of the mechanism for the dehydration of an amide to a nitrile using phosphorus pentoxide. Same mechanism and principles (good leaving group, exothermic) as discussed above.
here is ur answer Here is a mechanism for the dehydration of an acid to an anhydride using phosphorus pentoxide.
The OHOH group is not a very good leaving group. Even in simpler reactions like the dehydration of an alcohol to an olefin we often first convert the hydroxyl group into a better leaving group by protonation with acid or conversion to an inorganic ester (for example using thionyl chloride or phosphorus pentoxide). The same thing takes place here - we are converting the acid's hydroxyl group into a better leaving group.
Why is HPO3HPOX3 such a good leaving group? Look at all the resonance structures you can draw for the anion PO3−POX3X−. It's stability makes the reaction exothermic and strongly drives the dehydration process to the product side.
For completeness, here is a link to a drawing and discussion of the mechanism for the dehydration of an amide to a nitrile using phosphorus pentoxide. Same mechanism and principles (good leaving group, exothermic) as discussed above.
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