# How to determine if a base is bulky?

I remember my teacher saying that during E2 (elimination bimolecular) reactions of alkanes, if the strong base that is used as a reagent is a bulky one, it has higher probability of giving a Hofmann (less stable) product as the major product even if there are possibilities for a Saytzeff (or Zaitsev) product to form.

How should I find if a base is bulky or not?

Some bases like t-butoxide ion are pretty obvious. I usually just guess it is based on how much steric-clouded it seems when I draw a representation on a paper. Is there any better way to figure this out?

• Related: Is the -OCH3 group bulky? Dec 23 '20 at 22:00
• chemistry.stackexchange.com/questions/104019/… Dec 24 '20 at 1:05
• user55119's answer has the details, but the underlying point is that it's empirical. There isn't some theoretical cutoff where you perform some calculations and then it gives you a bulk coefficient $\xi$ where if $\xi > 4$ it's bulky and if $\xi \leq 4$ it's not. Well, maybe you can calculate the size, but then one should ask, exactly what size is considered "bulky"? which brings us back to square one. Dec 24 '20 at 2:07