This got me thinking. Who are the great teachers of chemistry? As in the case of the greatest chemist discussion, the answer seems to be easier to answer in case of physics. A roster of great twentieth-century physicist-teachers immediately brings to mind the names of Arnold Sommerfeld, Niels Bohr, Max Born, Ernest Rutherford, Robert Oppenheimer, Isidor Rabi, Wheeler and many others. What great scientists would populate a similar list of outstanding chemist-teachers?
Fist let's lay out the criteria for being a great teacher. Simply supervising a large number of PhD students may be important but is not enough since PhD students are usually essential for research and are also lamentably often utilized as cheap labor. Undergraduate teaching will definitely count highly on the list since it usually takes a genuine love of teaching to divert precious time toward elementary courses. Then there's the matter of pedagogy, often displayed through first-rate textbooks. Great chemists who made concerted efforts to educate through the writing of timeless textbooks will also count.
But ultimately, nothing counts as much as inspiring students and immersing them in the philosophy of your subject, giving them a sense of the "taste" of the discipline, communicating to them the excitement of doing research and asking questions that will stay with them throughout their careers. A great teacher who may not be ideally suited for classroom teaching will still make the list if he invites his students for long walks and afternoon tea to engage them in informal and intense discussions about science. For instance, Robert Oppenheimer almost never taught an undergraduate class and his lectures were often opaque to everyone but the best students. Yet he managed to create the finest school of modern physics in the United States in the 30s and 40s, largely because of his immense charisma and brilliance and the sense of truly working at the frontier of physics that he communicated to his students. After classes, Oppenheimer would often invite his students out for dinner and spend the evening listening to classical music and discussing physics. As Hans Bethe put it:
Probably the most important ingredient Oppenheimer brought to his teaching was his exquisite taste. He always knew what were the important problems, as shown by his choice of subjects. He truly lived with those problems, struggling for a solution, and he communicated his concern to the group
So who then are the great chemist-teachers? As usual this represents a limited collection of my personal favorites. Incidentally, the greatest chemist of the twentieth century was also one of its greatest teachers. When Linus Pauling was teaching undergraduates at Caltech and could not find a satisfactory textbook, he wrote his own. "General Chemistry" is still in print and still quite readable. With E. Bright Wilson, Pauling also wrote "Introduction to Quantum Mechanics", the first modern quantum chemistry textbook. And then there's of course the momentous "The Nature of the Chemical Bond" which was known not only for its science but for its superb pedagogy. Pauling's lecture demonstrations to undergraduates were also well-known. A student of his described how Pauling would rapidly juggle a lump of sodium in his hands and talk at length about sodium's vigorous reaction with water, all the while warily eyeing a beaker of water on the table. The lump would then "accidentally" fall into the beaker. While everyone including Pauling ducked, nothing would happen, and Pauling would nonchalantly add, "But its reaction with alcohol is much less violent". Another chemist who taught through explosions and colors was Hubert Alyea at Princeton. Sadly, the art of the lecture demonstration seems to be lost to modern chemical education.
Speaking of textbooks, one cannot forget the author as great teacher. Sadly many of them are now forgotten and deserve to be resurrected. For some reason British authors especially stand out as marvelous pedagogical expositors in the classical tradition. A true gem for instance is "Valence" by Oxford theoretical chemist Charles Coulson whose crystal clear treatment of quantum chemistry has stood the test of time. A fair number of students who trained with Coulson later became outstanding theoretical chemists in their own right. I would place him high on the list. Then there's Stuart Warren, coauthor of my favorite organic chemistry textbook who also wrote one of the definitive books on retrosynthetic analysis. And there's the little known and under-appreciated "Guidebook to Mechanism in Organic Chemistry" by Peter Sykes which in my opinion is the most devastatingly concise and clear treatment of the subject ever written. In Sykes's hands, nucleophilic substitution sounds like a well-crafted violin sonata.
Among American authors I would name Morrison and Boyd, not famous scientists but authors of an outstanding organic chemistry text (which unfortunately was not updated). Ernest Eliel's book taught stereochemistry to a generation of organic chemists and I have always had it on my shelf. There's F. Albert Cotton's definitive textbook on inorganic chemistry; Cotton was also known as a prolific trainer of PhDs. And there's biochemistry volumes by Albert Lehninger and Lubert Stryer which are both pillars of authority and clarity in their field.
In the early part of the century the center of scientific excellence was in Europe. The great European chemists Svante Arrhenius and Walther Nernst were both extremely influential as mentors. So were Robert Robinson and Leopold Ruzicka. Harvard chemist Theodore William Richards who won the Nobel Prize for his accurate determination of atomic weights deserves special mention; his students included G N Lewis, Roger Adams and James Bryant Conant. Lewis himself was the most influential chemist of his time and imparted his style of thinking to many outstanding chemists, including Glenn Seaborg.
Let's talk about the latter half of the century. Robert Burns Woodward did not teach undergraduate courses and in fact in his later years was known to be pre-occupied with his own research to the detriment of his students. Yet Woodward's influence was so towering that his students adopted his style merely by being around him. In his earlier years he was known as a great teacher, especially by way of his famous Thursday seminars which used to last into the night. Woodward's students have populated the corridors of organic chemistry and the impact of his way of doing chemistry is undeniable. So is E J Corey's. I don't know if Corey taught undergraduates, but he has trained hundreds of students and postdocs who have carried his science all around the world and the sheer reach of Corey's chemistry and philosophy is probably greater than of any organic chemist in history. A traditional pilgrimage to Corey's lab for a postdoc was like a mandatory pilgrimage to one of the great European centers of physics in the early twentieth century. Corey qualifies as a great guide in spite of some unfortunate stories from his lab.
Caltech chemist Jack Roberts also stands out for two things- training students like George Whitesides, and writing some great books; one of the earliest accounts of MO calculations for American students, a first-rate organic textbook co-authored with Marjorie Caserio and an excellent volume on NMR basics. Another great mentor is Ronald Breslow who has trained three generations of chemists that have filled up the top ranks of academic chemistry; Nobel laureate Robert Grubbs for instance got his PhD with Breslow. Finally I want to note Dudley Herschbach who was also known for teaching introductory chemistry at Harvard and who willingly accepted the responsibility of being the c0-master of a dorm.
We could go on. There are of course many who I have not noted, and I invite others to offer their own examples. Sadly this list is fundamentally unfair since it leaves out outstanding college professors who are not very well-known as scientists. Such a list would be especially valuable.
In an age where universities are increasingly weighing the value of professors based almost exclusively on their grant-winning capabilities, it's worth reminding our institutions that fifty years ago teaching was taken as seriously as research. And as the above examples demonstrate, there is absolutely no discrepancy between being a world-class scientist and a world-class teacher. Teaching introductory chemistry and being a Nobel laureate are not diametrically opposed concepts. In many ways mentorship goes much further than research ideas. It's a lesson worth remembering.