Since the knowledge of Organic reaction mechanism is essential for understanding the course of Organic chemistry, a study of Organic reaction mechanism now forms an essential part of the Organic chemistry courses in all the Universities. This book is intended for students at the graduate and postgraduate level. Due to wide coverage and simple style, students at all levels can get benefited from this book All topics have been selected with great care keeping in mind the needs of the students. Certain topics which are generally discussed in introductory books are excluded. Each chapter concludes with a set of review questions.