The theory of resonance and its application to organic chemistry

BOOK REVIEWS. THE AMERICAN ANNUAL OF PHOTOGRAPHY, Volume 59, 1945. 2oo pages, illustrations, 18 X 25 cms. Boston, American Photographic Publishing Co., I944. Price $.5o (paper). Lovers of the c a m e r a - - a n d their name is Legion--will accord its usualwelcome to the .American Annual of Photography, and this 1945 edition should in no way disappoint them. Even those who are content to admire the work of others may rejoice in the illustrations, and there is an article on "Photographing Dogs and Cats in the Home" with entrancing puppies and kittens to delight them. This is balanced by a discussion of present practice in medk-al photography with instructions in technique, and also by the opening article on "Aspects of Color" by Lloyd E. Varden. For h u m a n interest, there is an account of the life of Edwin Hale Lincoln, who won his national reputation with his marines, turning later to botany and the detailed pictures of wild flowers, while the paper on " P h o t o g r a p h y in the Study of Design" should satisfy the most convinced modernist. The Annual is now in its fifty-nlnth year and its continuing popularity seems richly deserved. E. EWlNG. THE THEORY OF RESONANCE AND ITS APPLICATION TO ORGANIC CHEMISTRY, by George Willard Wheland. 316 pages, tables and illustrations, 14 X 22 cms. New York, John Wiley and Sons, Inc.; London, Chapman and Hall, Ltd., 1944. Price $4.5o. The theory of resonance as applied to chemical structural theory is a man-made concept in a more fundamental sense than most other physical theories. I t does not correspond to any intrinsic property of the molecule itself, b u t instead it is only a mathematical device, deliberately invented by the physicist or chemist for his own convenience. The theory is perhaps the most important addition to chemical structural theory since the concept of the shared electron bond was introduced by G. N. Lewis. The purpose of this book as stated by the author is to provide a comprehensive survey of the subject to satisfy a need due to the scarcity of such in the literature. The procedure followed in this presentation begins with a t r e a t m e n t on the theory of resonance and the nature of valence. Here it is shown how the principle of resonance energy accounts in a qualitative way for the existence of covalent bonds and so, in a certain sense, for the existence of chemistry itself. Later its application to the less fundamental b u t more familiar problem of resonance among ordinary valence bond structures is taken up. Subsequently the steric effects of resonance are discussed and dipole moments, molecular spectra, chemical equilibrium, and chemical reaction. There are a number of useful appendixes and a subject and a u t h o r index. The work is presented from the chemical viewpoint, detailed and rigorous. It should go far toward accomplishing its purpose. R. H. OPPERMANN. ELECTRIC CIRCUITS AND FIELDS, by Harold Pender and S. Reid Warren, Jr. 534 pages, illustrations, 14 X 22 cms. New York and London, McGraw-Hill Book Co., Inc., 1943. This is a textbook on basic topics in electrical engineering for students who have had college courses in differential and integral calculus and in general physics. I t is arranged in two parts, the first being devoted to electric circuit problems, which invoFce the investigation of the measurable effects of electric currents, either constant or varying with time. Beginning with fundamental concepts, the work proceeds through direct current calculations, sources of electromotive force, introduction to transient phenomena, sinusoidal alternating currents, the 153