The book 'A Textbook of Organic Chemistry' was first published 40 years ago. Over the years it has become students' favourite because it explains the subject in the most student-friendly way and is revised regularly to keep itself updated with the latest in research. This edition presents the modern-day basic principles and concepts of the subject as per the CBCS of UGC guidelines Special emphasis has been laid on the mechanism and electronic interpretation of reactions of the various classes of compounds. It provides a basic foundation of the subject so that based on these, students are able to extrapolate, predict and solve challenging problems.New in this EditionA new chapter 'Energy in Biosystems' explores the fundamentals of biochemical reactions involved in storage as well as continuous usage of energy in biosystems, Structural theories like VB and MO, hybridization and orbital pictures of resonance, andhyperconjugation. ☐ Woodward-Fieser rules for calculating max, and Norrisch type I and II reactions of specialphotochemical C-C cleavage in the chapter on 'Electromagnetic Spectrum'.Polanyi-Hammond postulates and Curtin-Hammett principle, along with several newmechanisms, e.g., Favorskii, Baeyer-Villiger, and Birch, in Chapter 5.McMurry, Wittig, Stobbe, Darzen in Chapter 19. ■ Study of antib,iotics, antacids and antihistamines in the chapter on 'Chemotherapy Biodegradable and conducting plastics in the chapter on 'Synthetic @olymers andPlastics'.Benefits of 'Green Chemistry-the latest trend for sustainable chemistry as Appendix II.For BSc Chemistry (Pass & Honours) in accordance with CBCSKS Tewari is a former Head of the Department of Chemistry, Christ Church College, Kanpur. He taught organic chemistry to undergraduate and postgraduate students for more than three decades. He has been a very popular and devoted teacher due to his command on the subject. He has authored several books on chemistry.N K Vishnoi had relocated to England under HSMP programme of the UK government after serving as Associate Professor in Chemistry at Christ Church College, Kanpur for three decades. On his return, he joined NIIT University, Neemrana, as Professor. He has been associated as content provider in chemistry with egurucool.com, Career Launcher and several other organizations. He has also authored 'Advanced Practical Organic Chemistry.'