Bond Enthalpies
One way to estimate the enthalpy of a reaction is through the various bond enthalpies. Bond enthalpies are the various energies that different bonds between different molecules have. Bonds between different atoms will have different bond energies, so a single bond between carbon and fluorine will have a different bond enthalpy than a single bond between carbon and hydrogen. Also, single, double, and triple bonds will have different bond enthalpies. Note that the enthalpy of a double bond is not just double that of a single bond, and is different from the single bond all together.