Question

Which of the following modifications would make the hydroxyl substituent of an alcohol a better leaving group?

1) Deprotonation
2) Addition of an acid
3) Addition of a strong base
4) Conversion to an acetal

Answer 1

To make the hydroxyl substituent of an alcohol a better leaving group, the addition of an acid is the most effective method. Protonating the hydroxyl group converts it to water, a better leaving group. Therefore, the answer is 2) Addition of an acid.

Step-by-step explanation:

To determine which modification would make the hydroxyl substituent of an alcohol a better leaving group, it's important to understand the properties of good leaving groups in chemical reactions. Strong bases are poor leaving groups because they tend to hold onto protons, whereas weak bases are good leaving groups as they easily depart. Considering this, we can evaluate the options presented:

1. Deprotonation would increase the basicity of the hydroxyl group, making it worse as a leaving group.
2. Addition of an acid would protonate the hydroxyl group converting it from -OH to -OH2+, enhancing its ability as a leaving group because it leaves behind water, a weak base.
3. Addition of a strong base would not help in making the hydroxyl group a better leaving group.
4. Conversion to an acetal also would not improve the leaving group ability of the hydroxyl group in an alcohol.

Therefore, the answer is 2) Addition of an acid.