Question

This is for Organic II. Thank you!

obwodobo Rank each set of compounds in order of increasing acidity and explain the trend. Rank each set of compounds in order of increasing basicity and explain the trend.

Answer 1

1) Withdrawing groups (-NO₂, Br) increases the acidity of carboxylic acids by stabilizing their conjugate base. On the other hand, donating groups such as -OCH₃, -CH₃ destabilize conjugate base of carboxylic acids hence they decrease their acidity.

Here NO2 with drawing effect is greater than -Br and also -OCH3 donation ability is greater compared to -CH3. Considering these factors, acidity order increases in the following series.

III < IV < V < I < II

2) Withdrawing groups decrease the acidity of amines as they decrease overall electron density on the nitrogen(which acts as Lewis base). Similarly, donating groups increases the Lewis basic character amines by increasing the electron density on nitrogen. So, basic nature increases as follows

II< I < V< IV < III