I am considering Jacobs as the main text for the second term of a 2-cycle organic chemistry sequence.

Understanding Organic Reaction Mechanisms provides excellent coverage, at an introductory level, of all the elements of a standard physical organic chemistry course. Jacobs' organizing principle is structure-reactivity relationships. This leads to the drawback (for a book whose title proclaims its dedication to reaction mechanisms) that mechanistic types are not discussed until Chapter 6! This material might better have been covered earlier, to allow students to make more sense of the structure-reactivity relationships presented in Chapters 4 and 5. The first three chapters introduce chemical bonding; the roles of ions as acids, bases, and leaving groups; and the thermodynamic and kinetic aspects of reaction mechanisms.

The three final chapters constitute something I have not seen elsewhere: a primer on how to propose and prove reaction mechanisms, including three case studies taken from the primary literature and beautifully explained. Again, much of the material in these chapters, particularly Chapter 8, would better have been introduced earlier, to allow students to gain practice proposing mechanisms as they learn about the reactions of various classes of organic compounds.

End-of-chapter problems are provided, though not in great number. Most of the problems are at an elementary level, as befits the stated purpose of the text. Answers to problems are provided.

Understanding Organic Reaction Mechanisms is a good buy for any organic chemist, particularly for those teaching organic chemistry, and should be strongly considered as a supplementary text. It is also useful as a main text (supplemented by other material) for an intermediate-to-advanced undergraduate course in organic reaction mechanisms.