why formic acid is more acidic than benzoic acid?

why formic acid is more acidic than benzoic acid?


Grade:12th Pass

5 Answers

krishna sanapala
33 Points
11 years ago

If electron desity is more than the basic character is more. so in given formic acid and benzoic acid in benzoic acid electron density is more so benzoic acid is less acidic character so formic acid is more acidic character than the benzoic acid.

akshay akshay
17 Points
11 years ago

Bennzoic acid can act as both weak electron donating and electron withdrawing group. As carboxylate has two oxygen atoms benzene acts as weak electron donating group. Therefore acidity of benzoic acid is less than formic acid.

yours katarnak Suresh
43 Points
11 years ago

The pKa value of formic acid is 3.77 while that of benzoic acid is 4.202. This clearly indicates that formic acid is a stronger acid than benzoic acid. We know that the acidity in carboxylic acids is basically due to the resonance stabilised carboxylate group in which the negative charge is well accommodated between the two electronegative oxygen atoms. However, in case of benzoic acid, the benzene ring is attached directly to the carbonyl group. Thus there is additional resonance between the carbonyl group and the benzene ring, which disturbs the resonance in the carboxylate ion. In other words, the negative charge in the carboxylate group of formic acid is accommodated in a much better manner than in carboxylate group of benzoic acid. Hence formic acid furnishes H+ ions more easily than benzoic acid.

13 Points
7 years ago
in formic acid no me gp is present ..whil is is also not present in formc acid .but in formic acid the carbony carbon is e deficient ..that takes the e densiy from H making it acidic..while on the other hand in benzoic acid the electrophilic character is some what ful fil by aromatic ring ..due to which the actual acidic proton becomes less acidic.
Subhankar Pramanik
32 Points
6 years ago
Now acidic strength of formic acid is greater than benzoic acid (it`s clear from pka values of the two acids) . The reason can be explained as follows....... (I) In C6H5-COOH, due to the polarity of C=O grp the π bond shifts towards the o atom and a +ve chrge is developed over the c atom. Now to neutralise this chrge,the O atom of the -OH grp as well as the c atom of phenyl grp can donate it`s lone pair and π bond respectively to the c atom of the C=O grp ..But the donation if π bond from the phenyl grp is preferred due to resonance the o atom of the -OH grp fails to donate it`s lone pair and consequently doesn`t acquire any +be charge over it....(Ii) In formic acid there is only 1 corbon atom ..thus when chrge separation takes place between the C=O grp the only possibility is the donation of lone pair from the neighbouring O atom of -OH grp. This gives the o atom a +ve chrge and the H atom bonded to it can be easily released as H+.Thus formic acid is more acidic than benzoic acid Hope this answer is helpful

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