Question

Rank the following compounds in order of their reactivity toward nucleophilic acyl substitution. (Fastest first, slowest last) 2) (10 pts) Rank the following compounds in order of the following sets with respect to increasing acidity. (Least acidic first, most acidic last) b) Benzoic acid, para-nitrobenzoic acid, trinitrobenzoic acid 3) (5 pts) How can you explain the fact that 2-chlorobutanoic acid has a pKa- 2.86,3- chlorobutanoic acid has a pKa 4.05, 4-chlorobutanoic acid has a pKa-4.52, and butanoic acid itself has a pKa 4.82? BRIEFLY EXPLAIN USING NO MORE THEN 3 SENTENCES. DRAWING THE STRUCTURES WHILE EXPLAINING WILL PROBABLY HELP

Answer 1

The compounds can be ranked in order of increasing acidity as follows: benzoic acid < para-nitrobenzoic acid < trinitrobenzoic acid. The pKa values of 2-chlorobutanoic acid, 3-chlorobutanoic acid, 4-chlorobutanoic acid, and butanoic acid can be explained by the electron-withdrawing effect of the chlorine atom.

Step-by-step explanation:

The compounds can be ranked in order of increasing acidity by comparing the strength of their conjugate bases. Here is the ranking: benzoic acid < para-nitrobenzoic acid < trinitrobenzoic acid. This ranking is based on the inductive effects of the substituent groups. The nitro groups (-NO2) are electron-withdrawing groups that destabilize the negative charge on the conjugate base, making it more acidic.

The difference in pKa values between 2-chlorobutanoic acid, 3-chlorobutanoic acid, 4-chlorobutanoic acid, and butanoic acid can be explained by the electron-withdrawing effect of the chlorine atom. The chlorine atom withdraws electron density from the carboxylic acid group, making the conjugate base more stable and the acid more acidic.

Answer 2

Trinitrobenzoic acid > para nitro benzoic acid>benzoic acid

Nulceophilic acyl Substitution increases by electron withdrawing group (NO2) more the no of withdrawing groups more the reactivity

Since withdrawing group increases positive charge hence nucleophilie readily reacts.

Acidity of Carboxylic acid is explained by inductive effect

Withdrawing group (halogen) increases the acidity and acidity decreases with increasing the distance between halogen and COOH group

And lower the acidity higher the pka and Vice-Versa.

Hence 2-Chlorobutanoic acid has lower pka and more acidic than 3-chloro and 4-chlorobutanoic acids