Experimental and ab Initio Equilibrium Structure and Harmonic Force Field of 1,2,5-Oxadiazole

Characterization of the Isothermal Compression Behavior of LLM-172

“…Strong similarities exist between the vibrational patterns of LLM-172 and that of the parent 1,2,5-oxadiazole molecule − and its sulfur analog 1,2,5-thiadiazole . It is worth noting that the vibrational modes associated with the ring vibrations of LLM-172 and 1,2,5-thiadiazole show a closer correspondence than that of 1,2,5,-oxadiazole.…”

“…Under compression, the Raman spectra do not show any evidence of NO 2 detachment, which would be manifested as an abrupt shift in one (or more) of the NO 2 frequencies with pressure. However, the Raman spectra do show some evidence of the formation of a C−O−NO group, with small features 27 The appearance of these modes at pressures near 10 GPa suggests that some degree of decomposition begins at very low pressures, which is supported by the broadening and weakening of the X-ray diffraction features. These observations suggest that under slow compression the C−O−NO formation is favored over the proposed ring cleavage mechanism.…”

Microwave spectrum and structure of furfural

“…This might be the case for furfural which is rather heavy and has a low torsion frequency for the HCO group, namely, 127 cm À1 for cis and 146 cm À1 for trans [11]. Demaison, Rudolph and co-workers [30][31][32][33][34] applied the mass-dependent (r m ) method of Watson et al [35] to a variety of molecules (diatomic, linear, symmetric top Table 5 Rotational parameters of 13 C substituted furfural species Parameter [18]) and apply to the last digits shown. b Number of rotational transitions fit for each isotopolog.…”

Vibrational assignment of isoxazole aided by rovibrational data and density functional theory

“…(27) of [17], and turns out to be negligible (+0.0002 u Å 2 ). D elec for isoxazole is known to be À0.0088 u Å 2 [18]. D vib therefore accounts for +0.0701 u Å 2 , and the B3LYP value of +0.0708 u Å 2 is very close to this.…”

“…The FTIR spectrum is adapted from [5] and reproduced with permission. Table 4 Observed vibration-rotation constants (MHz) and inertial defects (u Å 2 ), with those from the anharmonic B3LYP/6-311+G(d,p) calculation Experimental a B3LYP anharmonic [18], and D cent = +0.0002 u Å 2 (see text).…”