Chemistry Class 12 NCERT Solutions: Chapter 12 Aldehydes Ketones and Carboxylic Acids Part 18

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Q: 8. Which acid of each pair shown here would you expect to be stronger?

(i)

(ii)

(iii)

(iv)

Q 8 iv Acid of each Pair

Q 8 Iv Acid of Each Pair

Q 8 iv Acid of each Pair

Answer:

(i)

Q 8 i The Electron Density on the O - H Bond

Q 8 I the Electron Density on the O - H Bond

Q 8 i The Electron Density on the O - H Bond

The effect of group increases the electron density on the bond. Therefore, release of proton becomes difficult. On the other hand, the effect of F decreases the electron density on the bond. Therefore, proton can be released easily. Hence, is a stronger acid than .

(ii)

Q 8 ii F has stronger -I effect than Cl

Q 8 Ii F Has Stronger -I Effect Than Cl

Q 8 ii F has stronger -I effect than Cl

F has stronger effect than . Therefore, can release proton more easily than . Hence, is stronger acid than .

(iii)

Q 8 iii 1 Inductive Effect Decreases with Increase in Distance

Q 8 Iii 1 Inductive Effect Decreases With Distance

Q 8 iii 1 Inductive Effect Decreases with Increase in Distance

Q 8 iii 2 Inductive Effect Decreases with Increase in Distance

Q 8 Iii 2 Inductive Effect Decreases With Distance

Q 8 iii 2 Inductive Effect Decreases with Increase in Distance

Inductive effect decreases with increase in distance. Hence, the +I effect of F in is more than it is in . Hence, is stronger acid than .

(iv)

(A)

Q 8 iv A Due to the −I Effect of F, it is Easier to Release Proton in the case of Compound A

Q 8 Iv a Due to the -I Effect of F, Easier to Release Proton

Q 8 iv A Due to the −I Effect of F, it is Easier to Release Proton in the case of Compound A

(B)

Q 8 iv B Release of Proton is Difficult due to the +I Effect of -CH 3 Group

Q 8 Iv B Release of Proton Difficult +I Effect of -CH 3 Group

Q 8 iv B Release of Proton is Difficult due to the +I Effect of -CH 3 Group

Due to the −I effect of F, it is easier to release proton in the case of compound (A). However, in the case of compound (B), release of proton is difficult due to the +I effect of group. Hence, (A) is a stronger acid than (B).