This book explores the fate of H isotopes in organic molecules from the perspective of equilibrium isotope fractionation. Using a novel combination of theoretical and experimental methods, it quantitatively investigates the magnitude of equilibrium H isotope fractionation and its temperature dependence, as well as the underlying chemistry, for various organic H sites common to sedimentary organic matter. The results serve as building blocks to calculate accurate fractionation factors for geo-relevant organic molecules without resorting to further molecular modeling. This knowledge has broad impacts on paleoclimate reconstructions, ecological studies, petroleum generation processes, and studies in biochemistry and astrobiology. This book also contributes to the methodology of compound-specific H isotope analysis by quantitatively evaluating the isotopic memory effects. Data has been organized in comprehensive tables and figures to facilitate use. Geochemistry, geobiology and environmental science researchers and students will find this book a valuable source of information.