203

to explain in a more convincing fashion the. fact that the N-N bond in NzO is somewhat longer than a triple bond, while the N-O bond length resembles that of a double bond. This point of view is essentially a reinterpretation of the “classical” VB explanation which involves resonance amongst such struc- tures as

_--.

N&O- -N=N+=O NiN;

etc. That is, the “three-electron bond” concept succeeds in avoiding mention of just the kind of thing which makes VB theory so hard to swallow.

I am not quite sure precisely at whom this book is aimed. Parts of it pro- vide very elementary descriptions of MO and VB theory, yet the arguments underlying the basic message are rather subtle. Experimentalists interested in structural problems will find much of this hard going, and theoreticians will also demand more detailed explanations.

I doubt whether Harcourt will convince the community of his viewpoint. His ideas are not straightforward. People like simple explanations: MO theory was basically accepted because of 0 2, and (simple) VB theory because of Hz. Nevertheless the problems attacked in this book will not go away. Most of us do not believe that MO theory in such situations is anything more than a game of noughts and crosses, and an alternative view presented by Harcourt deserves serious consideration.

J. G.

Studies in Physical and Theoretical Chemistry, Vol. 28, Chemical Applica- tions of Topology and Graph Theory, edited by R. B. King, Elsevier Science Publishing Co., Amsterdam, 1983, pp. xii + 494, price Dfl275.

It seems only yesterday that chemists were introduced to the power of group theory and matrix algebra. From the tremendous progress already made it is clear that theoretical chemists must now take aboard the language and techniques of graph theory in order to stay ahead in the relentless race to harness mathematics to chemical use.

This book contains the papers presented by some of the leading workers in this field held at the University of Georgia in April, 1983. A wide range of topics is covered including stereochemistry, inorganic cluster compounds, dynamic systems, reaction networks, polymers, liquia structure, biochem- istry and quantum chemistry.

N. Trinajstic has recently published an excellent text on “Chemical Graph Theory” (CRC Press, Boca Raton, Florida, 1983).

Having mastered this the general reader will be in a good position to appreciate the power of this increasingly successful approach as indicated in the more specialized volume reviewed here.

W. J. O.-T.