The spectroscopic value for the heat of formation of free CH and Herzberg's value for the heat of sublimation of graphite lead to a value of ∼137.9 kcal. for the C&trpbnd;C bond strength in acetylene. This value is employed in a study of the potential energy levels of that compound and is shown to be the only one consistent with the most recent studies of its absorption spectrum. The fact that the known energy levels of free CH fit into the scheme is further evidence for the 125.1 kcal. value for the heat of sublimation of graphite.
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