THE THEORY OR RESONANCE AND ITS APPLICATIONS TO ORGANIC CHEMISTRY
By George W. Wheland '28. JohnWiley & Sons, 1944, 316 pp. $4.50.
This excellent textbook grew out of a course of lectures presented by Professor Wheland during the last few years to advanced undergraduates and graduate students at the University of Chicago. It is "for readers who have a sound knowledge of elementary organic chemistry and some acquaintance with physical chemistry." Although it is written in terms familiar to the organic chemist, "its basis lies in the mathematical depths of quantum mechanics." The author has reached a good compromise between highly mathematical language and the descriptive approach most useful to the organic chemist.
The author states that the theory of resonance is the most important addition to chemical structural theory that has been made since the concept of the shared-electron bond was introduced by G. N. Lewis. Friends of Dr. Wheland who may lack the background necessary to enable them to assimilate everything in the text can perhaps enjoy the method by which he explains to the old-fashioned organic chemist that tautomerism and resonance hybrids are quite different. He makes the distinction between tautomerism and the newer concepts clear by the following analogy.
"A mule is a hybrid between a horse and a donkey. This does not mean that some mules are horses and the rest are donkeys, nor does it mean that a given mule is a horse part of the time and a donkey the rest of the time. Instead, it means that a mule is a new kind of animal, neither horse nor donkey but intermediate between the two and partaking to some extent of the character of each."
One can appreciate the above paragraph without understanding how it applies to molecular structure; but the analogy illustrates how interestingly Dr. Wheland elucidates the difficult subject. The result is a textbook which should be in the library of every chemist, and one which is rapidly being adopted by teachers of university classes in physico-organic chemistry.
