231468
Arrange the following in decreasing order of acidic strength. (i) Benzoic acid (ii) 4-nitrobenzoic acid (iii) 3, 4-dinitrobenzoic acid (iv) 4-methoxy benzoic acid
1 III $>$ II $>$ I $>$ IV
2 III $>$ II $>$ IV $>$ I
3 II $>$ III $>$ IV $>$ I
4 I $>$ II $>$ III $>$ IV
Explanation:
Since, electron donating groups decrease the acid strength, therefore, 4-methoxy benzoic acid is a weaker acid than benzoic acid. Further, since electronwithdrawing groups increase the acid strength, therefore, both 4-nitrobenzoic acid and 3, 4dinitrobenzoic acid are stronger acid than benzoic acid. Further, due to presence of an additional $\mathrm{NO}_{2}$ at $\mathrm{m}$ position with respect to $\mathrm{COOH}$ group, 3, 4dinitrobenzoic acid is a little stronger acid than 4- nitrobenzoic acid thus the overall acid strength increase in the order: 4-methoxy benzoic acid $<$ benzoic acid $<$ 4 - nitrobenzoic acid $<3$, 4-dinitrobenzoic acid.
JCECE - 2016
GENERAL ORGANIC CHEMISTRY
231470
Among the following which is least acidic?
1 Phenol
2 o-cresol
3 p-nitrophenol
4 p-chlorophenol
Explanation:
Nitro $\left(-\mathrm{NO}_{2}\right)$ and chloro $(-\mathrm{Cl})$ group has negative inductive effect $\left(-\mathrm{NO}_{2}\right.$ having more than $\left.-\mathrm{Cl}\right)$ and thus they pull electron density from phenolate ring making release of proton easier and the compound more acidic. On the other hand methyl $\left(-\mathrm{CH}_{3}\right)$ group has positive inductive effect making cresol less acidic. Their order of acidity is
JCECE - 2017
GENERAL ORGANIC CHEMISTRY
231471
Some meta-directing substituents in aromatic substituation are given. Which one is most deactivating?
1 $-\mathrm{SO}_{3} \mathrm{H}$
2 $-\mathrm{CN}$
3 $-\mathrm{COOH}$
4 $-\mathrm{NO}_{2}$
Explanation:
Deactivating strength of meta-directing substituents (or electron with drawing group -EWG) decreases with decrease in $-\mathrm{I}$ effect, which follows the order as $\mathrm{R}_{4} \mathrm{~N}^{\oplus}>-\mathrm{NO}_{2}>-\mathrm{CN}>-\mathrm{SO}_{3} \mathrm{H}>-\mathrm{COOH}>-\mathrm{F}>-\mathrm{Cl}$ $>-\mathrm{I}>-\mathrm{OR}>-\mathrm{OH}>-\mathrm{NH}_{2}>-\mathrm{C}_{6} \mathrm{H}_{5}$
JCECE - 2017
GENERAL ORGANIC CHEMISTRY
231473
The most stable carbonium ion among the following is
Delocalization and $+\mathrm{I}$ effect increase the stability of $+\mathrm{I}$ effect. Delocalization is dominating factor. Hence, the most stable carbocation or carbonium is- $\mathrm{C}_{6} \mathrm{H}_{5}-\stackrel{+}{\mathrm{C}}-\mathrm{C}_{6} \mathrm{H}_{5}$. Hence, (c) option is correct. The order of stability is-
231468
Arrange the following in decreasing order of acidic strength. (i) Benzoic acid (ii) 4-nitrobenzoic acid (iii) 3, 4-dinitrobenzoic acid (iv) 4-methoxy benzoic acid
1 III $>$ II $>$ I $>$ IV
2 III $>$ II $>$ IV $>$ I
3 II $>$ III $>$ IV $>$ I
4 I $>$ II $>$ III $>$ IV
Explanation:
Since, electron donating groups decrease the acid strength, therefore, 4-methoxy benzoic acid is a weaker acid than benzoic acid. Further, since electronwithdrawing groups increase the acid strength, therefore, both 4-nitrobenzoic acid and 3, 4dinitrobenzoic acid are stronger acid than benzoic acid. Further, due to presence of an additional $\mathrm{NO}_{2}$ at $\mathrm{m}$ position with respect to $\mathrm{COOH}$ group, 3, 4dinitrobenzoic acid is a little stronger acid than 4- nitrobenzoic acid thus the overall acid strength increase in the order: 4-methoxy benzoic acid $<$ benzoic acid $<$ 4 - nitrobenzoic acid $<3$, 4-dinitrobenzoic acid.
JCECE - 2016
GENERAL ORGANIC CHEMISTRY
231470
Among the following which is least acidic?
1 Phenol
2 o-cresol
3 p-nitrophenol
4 p-chlorophenol
Explanation:
Nitro $\left(-\mathrm{NO}_{2}\right)$ and chloro $(-\mathrm{Cl})$ group has negative inductive effect $\left(-\mathrm{NO}_{2}\right.$ having more than $\left.-\mathrm{Cl}\right)$ and thus they pull electron density from phenolate ring making release of proton easier and the compound more acidic. On the other hand methyl $\left(-\mathrm{CH}_{3}\right)$ group has positive inductive effect making cresol less acidic. Their order of acidity is
JCECE - 2017
GENERAL ORGANIC CHEMISTRY
231471
Some meta-directing substituents in aromatic substituation are given. Which one is most deactivating?
1 $-\mathrm{SO}_{3} \mathrm{H}$
2 $-\mathrm{CN}$
3 $-\mathrm{COOH}$
4 $-\mathrm{NO}_{2}$
Explanation:
Deactivating strength of meta-directing substituents (or electron with drawing group -EWG) decreases with decrease in $-\mathrm{I}$ effect, which follows the order as $\mathrm{R}_{4} \mathrm{~N}^{\oplus}>-\mathrm{NO}_{2}>-\mathrm{CN}>-\mathrm{SO}_{3} \mathrm{H}>-\mathrm{COOH}>-\mathrm{F}>-\mathrm{Cl}$ $>-\mathrm{I}>-\mathrm{OR}>-\mathrm{OH}>-\mathrm{NH}_{2}>-\mathrm{C}_{6} \mathrm{H}_{5}$
JCECE - 2017
GENERAL ORGANIC CHEMISTRY
231473
The most stable carbonium ion among the following is
Delocalization and $+\mathrm{I}$ effect increase the stability of $+\mathrm{I}$ effect. Delocalization is dominating factor. Hence, the most stable carbocation or carbonium is- $\mathrm{C}_{6} \mathrm{H}_{5}-\stackrel{+}{\mathrm{C}}-\mathrm{C}_{6} \mathrm{H}_{5}$. Hence, (c) option is correct. The order of stability is-
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GENERAL ORGANIC CHEMISTRY
231468
Arrange the following in decreasing order of acidic strength. (i) Benzoic acid (ii) 4-nitrobenzoic acid (iii) 3, 4-dinitrobenzoic acid (iv) 4-methoxy benzoic acid
1 III $>$ II $>$ I $>$ IV
2 III $>$ II $>$ IV $>$ I
3 II $>$ III $>$ IV $>$ I
4 I $>$ II $>$ III $>$ IV
Explanation:
Since, electron donating groups decrease the acid strength, therefore, 4-methoxy benzoic acid is a weaker acid than benzoic acid. Further, since electronwithdrawing groups increase the acid strength, therefore, both 4-nitrobenzoic acid and 3, 4dinitrobenzoic acid are stronger acid than benzoic acid. Further, due to presence of an additional $\mathrm{NO}_{2}$ at $\mathrm{m}$ position with respect to $\mathrm{COOH}$ group, 3, 4dinitrobenzoic acid is a little stronger acid than 4- nitrobenzoic acid thus the overall acid strength increase in the order: 4-methoxy benzoic acid $<$ benzoic acid $<$ 4 - nitrobenzoic acid $<3$, 4-dinitrobenzoic acid.
JCECE - 2016
GENERAL ORGANIC CHEMISTRY
231470
Among the following which is least acidic?
1 Phenol
2 o-cresol
3 p-nitrophenol
4 p-chlorophenol
Explanation:
Nitro $\left(-\mathrm{NO}_{2}\right)$ and chloro $(-\mathrm{Cl})$ group has negative inductive effect $\left(-\mathrm{NO}_{2}\right.$ having more than $\left.-\mathrm{Cl}\right)$ and thus they pull electron density from phenolate ring making release of proton easier and the compound more acidic. On the other hand methyl $\left(-\mathrm{CH}_{3}\right)$ group has positive inductive effect making cresol less acidic. Their order of acidity is
JCECE - 2017
GENERAL ORGANIC CHEMISTRY
231471
Some meta-directing substituents in aromatic substituation are given. Which one is most deactivating?
1 $-\mathrm{SO}_{3} \mathrm{H}$
2 $-\mathrm{CN}$
3 $-\mathrm{COOH}$
4 $-\mathrm{NO}_{2}$
Explanation:
Deactivating strength of meta-directing substituents (or electron with drawing group -EWG) decreases with decrease in $-\mathrm{I}$ effect, which follows the order as $\mathrm{R}_{4} \mathrm{~N}^{\oplus}>-\mathrm{NO}_{2}>-\mathrm{CN}>-\mathrm{SO}_{3} \mathrm{H}>-\mathrm{COOH}>-\mathrm{F}>-\mathrm{Cl}$ $>-\mathrm{I}>-\mathrm{OR}>-\mathrm{OH}>-\mathrm{NH}_{2}>-\mathrm{C}_{6} \mathrm{H}_{5}$
JCECE - 2017
GENERAL ORGANIC CHEMISTRY
231473
The most stable carbonium ion among the following is
Delocalization and $+\mathrm{I}$ effect increase the stability of $+\mathrm{I}$ effect. Delocalization is dominating factor. Hence, the most stable carbocation or carbonium is- $\mathrm{C}_{6} \mathrm{H}_{5}-\stackrel{+}{\mathrm{C}}-\mathrm{C}_{6} \mathrm{H}_{5}$. Hence, (c) option is correct. The order of stability is-
231468
Arrange the following in decreasing order of acidic strength. (i) Benzoic acid (ii) 4-nitrobenzoic acid (iii) 3, 4-dinitrobenzoic acid (iv) 4-methoxy benzoic acid
1 III $>$ II $>$ I $>$ IV
2 III $>$ II $>$ IV $>$ I
3 II $>$ III $>$ IV $>$ I
4 I $>$ II $>$ III $>$ IV
Explanation:
Since, electron donating groups decrease the acid strength, therefore, 4-methoxy benzoic acid is a weaker acid than benzoic acid. Further, since electronwithdrawing groups increase the acid strength, therefore, both 4-nitrobenzoic acid and 3, 4dinitrobenzoic acid are stronger acid than benzoic acid. Further, due to presence of an additional $\mathrm{NO}_{2}$ at $\mathrm{m}$ position with respect to $\mathrm{COOH}$ group, 3, 4dinitrobenzoic acid is a little stronger acid than 4- nitrobenzoic acid thus the overall acid strength increase in the order: 4-methoxy benzoic acid $<$ benzoic acid $<$ 4 - nitrobenzoic acid $<3$, 4-dinitrobenzoic acid.
JCECE - 2016
GENERAL ORGANIC CHEMISTRY
231470
Among the following which is least acidic?
1 Phenol
2 o-cresol
3 p-nitrophenol
4 p-chlorophenol
Explanation:
Nitro $\left(-\mathrm{NO}_{2}\right)$ and chloro $(-\mathrm{Cl})$ group has negative inductive effect $\left(-\mathrm{NO}_{2}\right.$ having more than $\left.-\mathrm{Cl}\right)$ and thus they pull electron density from phenolate ring making release of proton easier and the compound more acidic. On the other hand methyl $\left(-\mathrm{CH}_{3}\right)$ group has positive inductive effect making cresol less acidic. Their order of acidity is
JCECE - 2017
GENERAL ORGANIC CHEMISTRY
231471
Some meta-directing substituents in aromatic substituation are given. Which one is most deactivating?
1 $-\mathrm{SO}_{3} \mathrm{H}$
2 $-\mathrm{CN}$
3 $-\mathrm{COOH}$
4 $-\mathrm{NO}_{2}$
Explanation:
Deactivating strength of meta-directing substituents (or electron with drawing group -EWG) decreases with decrease in $-\mathrm{I}$ effect, which follows the order as $\mathrm{R}_{4} \mathrm{~N}^{\oplus}>-\mathrm{NO}_{2}>-\mathrm{CN}>-\mathrm{SO}_{3} \mathrm{H}>-\mathrm{COOH}>-\mathrm{F}>-\mathrm{Cl}$ $>-\mathrm{I}>-\mathrm{OR}>-\mathrm{OH}>-\mathrm{NH}_{2}>-\mathrm{C}_{6} \mathrm{H}_{5}$
JCECE - 2017
GENERAL ORGANIC CHEMISTRY
231473
The most stable carbonium ion among the following is
Delocalization and $+\mathrm{I}$ effect increase the stability of $+\mathrm{I}$ effect. Delocalization is dominating factor. Hence, the most stable carbocation or carbonium is- $\mathrm{C}_{6} \mathrm{H}_{5}-\stackrel{+}{\mathrm{C}}-\mathrm{C}_{6} \mathrm{H}_{5}$. Hence, (c) option is correct. The order of stability is-
ring making release of proton easier and the compound more acidic. On the other hand methyl $\left(-\mathrm{CH}_{3}\right)$ group has positive inductive effect making cresol less acidic. Their order of acidity is
