I would like to know if whom can be used in this sentence:
I commend the authors for discussing the discrepancy between minority medical students and the disproportionate percentage of whom apply to plastic surgery.
Your sentence does not make sense. For the word "whom" to be used correctly, the word "and" should not be there. But if we remove the "and", the sentence is still wrong:
I commend the authors for discussing the discrepancy between minority medical students, a disproportionate percentage of whom apply to plastic surgery. ❌
The part after the comma is now providing non-essential information and can be dropped, and you're left with an incomplete sentence:
I commend the authors for discussing the discrepancy between minority medical students ... [and what?]
Many people seem to be under the impression that "whom" is just a universal way to refer to a person mentioned earlier in the sentence. This is not the case. Here is a site that summarizes the usage of "of whom" and "of which": https://www.grammarbank.com/whose-of-which-of-whom.html. I'm sure there are many others.
You can remove the misused "whom" from your sentence and rewrite it correctly as:
I commend the authors for discussing the discrepancy between minority medical students and the disproportionate percentage of them who apply to plastic surgery.
The problem now is with the meaning. How can you have a "discrepancy" between one group and another?
I would rewrite your sentence as:
I commend the authors for discussing the disproportionate percentage of minority medical students who wish to specialize in plastic surgery.
I have changed "apply to", which is misused in your original sentence. (Medical students may colloquially say "I applied to plastic surgery", but this is short for something like "I applied for admission into the plastic surgery department".) I still don't like the verb "discuss". It would be better to explain what specifically the authors did that was so commendable; e.g, "drawing attention to", "studying".
No. It almost works, similar to
We received many cancellations today, the majority of which were weather related.
We saw all our neighbors today at the grocery store, many of whom were preparing for tomorrow's expected snow storm.
But you have to make sure that when you use "discrepancy" you are comparing one kind of apple to another kind of apple.
You'll get into less trouble if you try to use simple sentences (i.e. not compound) as much as possible. The easy way to do this is by reading a few pages of Hemingway every day before you write.
I commend the authors for pointing out the disproportionate percentage of minority medical students who apply to plastic surgery.
Extra bonus: you may want to consider using a more old-fashioned style that shifts the focus away from the author (you):
The authors must be commended for etc.