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Shweta Thakur posted an Question

August 03, 2020 • 23:06 pm

30 points

IIT JAM
Chemistry (CY)

Why methanoic acid is more acidic than benzoic acid .....as both conjugate base dtabilize by resonance so how

why methanoic acid is more acidic than benzoic acid b

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Dinesh khalmaniya 1 Best Answer

A molecule which can release a proton easily is more acidic. In other words, if the anion that is formed after removal of proton is more stable than that molecule will be more acidic. Now, take the case of formic and benzoic acid. In benzoic acid the benzoate anion formed is destabilized by the +R effect (though -I effect is also there which will try to somewhat stabilize the anion but its effect is less as compared to +R) whereas there is no such effect in case of formic acid. So formate ion is more stable than benzoate ion. Therefore, formic acid is more acidic than benzoic acid. Also now consider ethanoic acid and benzoic acid. In this case benzoic acid is more acidic than ethanoic acid. Because in benzoic both effect +R (try to destablize anion) and -I (try to stablize anion) are operating. One is donating other is withdrawing. But in ethanoic acid two effects are there and both are donating i.e +I and hyperconjugation effect which will destablize the anion and therefore less acidic than benzoic acid.
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got it Shweta??
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Shweta please respond
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sry sir actually I donot get any notification
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thanku so much sir
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for answer
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so c6h5 is electron releasing as well as acceptor
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yes
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i explained both the case why methanoic acid is more acidic and why acetic acid is less Acidic than benzoic acid
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yes, i know reason given by other facilities that due to equivalent RS , methanoic acid is more acidic than benzoic acid so you should cross question because acetic acid also have equivalent RS so why not more Acidic than Benzoic acid
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Priyanshu kumar

Shweta in methanoic acid equivalent resonating structure is formed...so thats why it is most stable
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When resonating structure is equivalent then it becomes most stable
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equivalent ?
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wait i m drawing
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check this
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got this shweta??
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ok sir
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👍😊
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