Microwave spectrum of benzoic acid

A broadband Fourier-transform microwave spectrometer with laser ablation source: The rotational spectrum of nicotinic acid

“…The values of the inertial defect given in Table 1 for nicotinic acid can be attributed to the contribution of the large amplitude out of plane vibrations of the carboxyl group, especially the torsional vibration. In fact, the values in Table 1 are almost equal to that found for benzoic acid (D = À0.366(2) uÅ 2 ) [23] and similar to the value for salicylic acid (D = À0.254(2) uÅ 2 ) [24]. Both molecules have been reported to be planar.…”

Unveiling the Shape of Aspirin in the Gas Phase

“…The planar moment of inertia P cc =( I a + I b − I c )/2=∑ i m i c i 2 , where m i and c i are, respectively, the mass and c coordinate of atom i , gives the mass extension out from the ab inertial plane. For example, salicylic17 and benzoic acids18 were reported to be planar and show P cc values of 0.127 and 0.183 uÅ 2 , respectively. For a planar skeleton of aspirin only the methylic hydrogen atoms would contribute to the planar moment as in methylsalicylate19 and this would give a value of P cc close to ${I_{{\rm{CH}}_{\rm{3}} } /2}$ as determined from the internal rotation analysis.…”

Theoretical quantum chemical study of benzoic acid: Geometrical parameters and vibrational wavenumbers

“…It is the simplest aromatic carboxylic acid, and it is also one of the most important acids in chemistry. Therefore, it has been the subject of several studies during the last two decades 1–4. However, its structure has been reported only theoretically 2 at HF and MP2 levels with the 6‐31G* basis set, and experimentally in the solid state by x‐ray crystallography 5.…”