The first ionization constants (pK_a values) | vedclass

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(A) The acidic strength of dicarboxylic acids depends on the distance between the two carboxylic acid groups.As the number of carbon atoms between the

Vedclass · Accepted Answer

$pK_1 > pK_2 > pK_3$

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(A) The acidic strength of dicarboxylic acids depends on the distance between the two carboxylic acid groups.As the number of carbon atoms between the two $-COOH$ groups increases,the electron-withdrawing inductive effect ($-I$ effect) of one $-COOH$ group on the other decreases.Oxalic acid $(HOOC-COOH)$ has $0$ carbon atoms between the groups.Malonic acid $(HOOC-CH_2-COOH)$ has $1$ carbon atom between the groups.Heptanedioic acid $(HOOC-(CH_2)_5-COOH)$ has $5$ carbon atoms between the groups.Acidic strength decreases as the distance increases: $	ext{Oxalic} > 	ext{Malonic} > 	ext{Heptanedioic}$.Since $pK_a = -\log(K_a)$,a higher $K_a$ corresponds to a lower $pK_a$.Therefore,the order of $pK_a$ values is $pK_1 Option $(a)$ states $pK_1 > pK_2 > pK_3$,which is the incorrect order.

The first ionization constants ($pK_a$ values) for the following dicarboxylic acids are given:
Oxalic acid: $pK_1$
Malonic acid: $pK_2$
Heptanedioic acid: $pK_3$
Which of the following represents the incorrect order of their $pK_a$ values?

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The first ionization constants ($pK_a$ values) for the following dicarboxylic acids are given:Oxalic acid: $pK_1$Malonic acid: $pK_2$Heptanedioic acid: $pK_3$Which of the following represents the incorrect order of their $pK_a$ values?