The aims of this study is to investigate the effects of functional groups like -C=C- and C-OH on variation of higher heating values (HHV) of organic compounds. HHV of fuel hydrocarbons, gaseous and liquids including single bonded and multiple bonded carbons and green tea polyphenols (GTP) were determined by using Bomb Calorimeter. It was observed that, multiple bonded carbon and oxygen bonded carbon i.e. -C=C- and -C-O- result in less carbon reduced state while, also increase endothermicity of reactants by changing hybridization state with more s-character and hence, contribute to lower level of HHV. Besides, hydrogen bonding was also considered as the major cause of the difference in HHV of fuel hydrocarbons having the same molecular formula but different oxygen-bearing functional groups due to structure stabilization. These statements were further supported by the combination of Fourier transform infra-red spectra (FTIR) and HHV calculation of raw GTP (set as a representative of biomass) and its solid products obtained at 250 degrees C and 350 degrees C by thermal treatment done by using high temperature tube furnace.