Vibrational spectroscopy and DFT calculations of N,N′-dicyclohexylcarbodiimide

Infrared (IR) and Raman spectra were obtained for N,N′ dicyclohexylcarbodiimide (DCC) in the solid state and in CHCl3 solution. Structures and vibrational spectra of isolated, gas-phase DCC molecules with C2 and Ci symmetries, computed at the B3-LYP/cc-pVTZ level, show that the IR and Raman spectra provide convincing evidence for a C2 structure in both the solid state and in CHCl3 solution. Using a scaled quantum-chemical force field, these density functional theory calculations have provided detailed assignments of the observed IR and Raman bands in terms of potential energy distributions. Comparison of solid-state and solution spectra, together with a Raman study of the melting behaviour of DCC, revealed that no solid-state effects were evident in the spectra.