Gas-Phase Infrared and NMR Investigation of the Conformers
of Diacetone Diperoxide (DADP)
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Abstract
Gas-phase infrared measurements of
diacetone diperoxide (DADP)
indicate a chair conformation with less than 5% of the predicted twist
conformer. Vibrational frequencies are very similar to those previously
measured in the solid state. Solution NMR measurements using 2D exchange
spectroscopy (EXSY) also set a very low maximum limit on the equilibrium
population of the twist conformer, with a room-temperature free-energy
difference in excess of 14.5 kJ/mol. These experimental results are
in accord with high-level quantum calculations incorporating full
thermochemistry and solvation effects, which indicate a free-energy
difference in the range of 14.7β17.5 kJ/mol in polar solvents