About the Book: For a very long time the need was felt by graduate and postgraduate students of Chemistry of almost all colleges and of Indian Universities for a book dealing with advanced mechanistic organic chemistry written in understandable language and with suitable examples which can be easily grasped to make their concept clear. Besides students, this has also been the requirement of teachers teaching advanced mechanistic organic chemistry. Till about 1959 there appears to be the only book by E.S. Gould (Structure and Mechanism of Organic Chemistry) but the examples mentioned in it are so difficult at several places that they elude the comprehension of even teachers, not to talk of students. Around sixties appeared the book by Jerry March (Advanced Organic Chemistry, Reactions, Mechanism and Structure). It was definitely a much better advance than that of Gould, but it has been made so bulky that its cost has become prohibitive. It adores the racks and shelves of libraries. In view of the above difficulties of teacher and students, the present book has been brought out. Some of its special chapters are the Pericyclic Reactions, which includes Cheletropic, Electrocyclic, sigmatropic and cycloaddition reactions. The concept of stereochemistry and conformation deserve special attention not because they cater to the needs of higher students, but they are immensely useful for candidates trying for UGC and CSIR sponsored competitive examinations, but also those preparing for Union Public Service Commission and State Public Service Commission Exams. The candidates will find the chapters immensely useful and is sure to rouse interest in them in knowing more about mechanistic chemistry. Spectroscopy is another topic, a good knowledge of which is expected from any good chemist. The spectroscopy finds immense applications in the identification of several unknown compounds in the field of research and medicine. Here one has to be very careful in elucidating the correct structure of entities. Moreover, in every examination (Competitive or regular) one has to show his skill in the area of spectroscopy and therefore chapters on spectroscopy giving a clear and lucid account is also noteworthy. About the Author: After taking the M.Sc. degree from the Allahabad University, the author started his teaching career in 1951 from the St. Andrew`s College, Gorakhpur when he was appointed a lecturer in Organic Chemistry there. While teaching-chemistry at this college, he developed interest in mechanistic Organic Chemistry. His interest in organic reaction mechanism become deeper when he started research work under the supervision of noted Prof. R.C. Mehrotra and under whose guidance he obtained his Ph.D. degree. The author joined the Gorakhpur University as a lecturer in the department of Chemistry in 1967. His close contact with Prof. R.P. Rastogi there initiated and stimulated him to undertake deeper studies of Organic Reaction Mechanism. He has brought out several research papers on Organosilicon and Organophosphorus Compounds. Several scholars have obtained the Ph.D. degree under his supervision. The author has attended National and International Symposia in Chemistry. He is the author of several books and articles and has published a large number of research papers in several journals of international repute.