This book is intended for the students of organic chemistry. Our text book can serve as a supplement for Heterocyclic Chemistry lecture text book. It can also be used as a 'stand-alone' text book for undergraduate and postgraduate levels for all Indian universities. This book is written in the form of ''a lecture series'' for easy reading and understanding. Nomenclature of various heterocycles, Mechanisms and Reactions of Pyridines are provided throughout the textbook. I hope that this book will be very helpful for the aspirants of all competitive exams related to chemistry like IIT-JAM, CSIR-UGC (NET/JRF), GATE, SET, TIFR, BARC, IISc, DRDO, ONGC, NPTC etc.