George Olah, 1994 Nobelist in chemistry, has passed away. Yet another of the extremely distinguished list of Hungarian-born scientists of the 20th century, Olah is remembered for (among other things) his pioneering work with “superacid” solutions as a means of studying carbocations directly. This led him, famously, into a long-running dispute with H. C. Brown on the structure of the norbornyl cation, a controversy that was still reverberating a bit even when I was in school (and whose final shot was fired just recently). Suffice it to say that Olah and his camp were correct – the structure first proposed by Saul Winstein back in the 1940s is the real one, although Winstein himself did not live to see his idea completely vindicated.
He was correct about a lot of other things as well, and he had a long and productive career in both the chemical industry and at USC. His work provided new reagents, new synthetic methods, and above all a wealth of insights into chemical reactions in general. Fewer and fewer chemists of his era are left.
Update: added some more history to the post, of which there is a lot.