What makes dimethyl compounds so extreme? I've noticed that dimethyl compounds tend to have extreme reactive, including bioreactive, characteristics.

Am I being misled by anecdotal selection bias, or is this generally true.  And if generally true, are there clear theoretical explanations as to why?

Examples that come to mind:


Dimethyl sulfoxide (DMSO) readily penetrates skin, and can carry lots of things across the skin barrier along with itself.
Miniscule amounts of dimethyl mercury will not only penetrate skin and many common PPE but are also irreversibly lethal.
Many dimethyl-metals are pyrophoric (i.e., they auto-ignite in a standard atmosphere).
This is because of two trivial facts, one from chemistry and another from math: (1) methyl is the smallest organic radical, and (2) it is not uncommon for a function to reach an extremum at the border of its domain.

Arguably, this is not even true in any significant way. Not sure about DMSO, but I firmly believe that organic compounds of mercury are all about as deadly as dimethylmercury. Well, those with bigger organic radicals might be slightly less dangerous because they are not quite as good at penetrating the cell barriers, or lower solubility, or because they contain less mercury per gram. The maximum is probably reached at methyl; but the maximum is not sharp.

All that applies to pyrophoric metalorganics as well.

So it goes.