Why it is difficult to remove chlorine as nucleophilic from benzene rather than alkyl Halide?

1 Answer
Mar 4, 2018

Consider the cases you describe, respectively,

puu.sh

In most introductory courses, it's satisfactory to remember that nucleophilic attacks generally don't occur at anything with more #"s"# character than an #"sp"^3# orbital.

If that doesn't satisfy you, consider:

In nucleophilic substitution, we want to keep things very lower in energy. The lowest energy unoccupied molecular orbital is generally a #pi# orbital, not a #sigma# orbital.

Attacking the latter will result in a higher energy transition state, which is unlikely given the general theme in chemistry is stability.

For a more detailed explanation, I'd suggest this discussion.