The study of Pharmaceutical Organic Chemistry is a cornerstone of the pharmaceutical sciences, providing a critical understanding of the chemical foundations that underpin drug design, synthesis, and action. This textbook, "Pharmaceutical Organic Chemistry – I," is designed to serve as an introductory guide for students, educators, and professionals who are beginning their journey into this fascinating field. The content of this book is meticulously structured to provide a comprehensive yet accessible exploration of the fundamental concepts of organic chemistry as they relate to pharmaceuticals. Starting with the basics of chemical reactions, molecular structure, and functional groups, the text gradually progresses to more complex topics such as reaction mechanisms, stereochemistry, and the synthesis of various organic compounds used in the pharmaceutical industry. The aim is to build a solid foundation that will support further study and application in the field. In crafting this book, special attention has been given to aligning the material with the needs of students. Each chapter is designed to not only impart theoretical knowledge but also to encourage practical understanding through examples, exercises, and real-world applications. The integration of qualitative tests, structure elucidation, and discussions on the uses of specific compounds provides a holistic view that bridges the gap between theory and practice. The importance of this subject in the broader context of pharmaceutical sciences cannot be overstated. A deep understanding of organic chemistry is essential for anyone involved in the development of new drugs, the improvement of existing therapies, or the advancement of medicinal chemistry. By mastering the concepts presented in this book, students will be well-equipped to tackle the challenges of drug discovery and development. I hope that this book will serve as a valuable resource for those studying Pharmaceutical Organic Chemistry, helping them to gain the knowledge and confidence needed to excel in their academic and professional endeavors. It is my sincere hope that the readers find this text not only informative but also inspiring, as they embark on their journey to contribute to the vital field of pharmaceutical sciences. I extend my best wishes to all the readers and students who will use this book as a tool to further their understanding of organic chemistry and its applications in the pharmaceutical world. May it serve as a stepping stone toward greater achievements in your academic and professional careers.