Mechanisms galore

Organic reaction mechanisms 
M. G?mez Gallego and M. A. Sierra, 
Berlin, Germany: Springer-Verlag | 2004 | 290pp | ?35.00 | ISBN 3540003525 
Reviewed by Jim Iley 

What resources do you need to teach mechanistic organic chemistry? More often than not, quick access to appropriate, contemporary examples that can be used to illustrate important learning objectives. For that reason alone I can commend Gomez Gallego and Sierra’s book which has as its by-line ’40 solved cases’. 

The book is well organised. The 40 cases are arranged into three levels according to difficulty. Each case follows a similar, and extremely helpful, learning and teaching format.  

A brief introduction to the problem is followed by the presentation of relevant experimental - or in some cases theoretical - data. A discussion of the observations in terms of the potential, and most consistent, reaction pathways ensues, followed by a summary of the important points. There are sometimes additional questions (and answers), and always appropriate literature references to the papers on which the case was based. The scope of the examples is a real asset. Want an example on pH-rate profiles? It’s here (hydrolysis of 2-aminobenzoates). Want an example of a change in rate limiting step, or a Br?nsted plot? It’s here (sulfamate aminolysis).  

The references are also valuable. They are constrained to a couple, at most, per case study and the majority were published since 2000. But what I liked most were the carefully argued discussions. These continually place emphasis on the experimental observations and lead the reader to understand how certain ones are consistent with some mechanisms but not others. By clearly demonstrating how the observations can be pieced together like a jigsaw, the authors impart the process of establishing the most plausible reaction mechanism. 

But what of the book’s less positive aspects? More careful editing would remove the idiosyncratic grammar, spelling, punctuation and hyphenation that detract from its reading in several places. More worryingly, errors in some mechanisms do not inspire confidence. Take case study 16; the cation radical of a carboxylic acid is shown to transfer a hydrogen, to an alkoxide ion at that, as ’H^-’. Not once, but twice! In a book about how to elucidate and write a reaction mechanism, this sort of error is unforgiveable.  

The structure and organisation of the book as a whole is confusing. Why, for example, is a case study on the sulfenylation of indole, interspersed between three case studies on differing aspects of carbonyl chemistry? And why have these case studies been chosen as opposed to any other. Why not more enolate chemistry? Why not metal-catalysed carbon-carbon bond forming reactions (Heck, Stille and so on)? 

Organic reaction mechanisms  is aimed at ’the advanced undergraduate’. I would be surprised if many such individuals will be keen enough to go out and buy a copy. But, despite the shortcomings, I can see it becoming a very useful resource for educators at advanced undergraduate and postgraduate level.