The Microwave Spectrum of Oxazole I. The Complete Structure by DRM Microwave Spectroscopy

Abstract

Double resonance modulation (DRM) microwave spectroscopy has been used to determine the complete substitution structure of oxazole. Isotopic species spectra associated withWith uncertainties below 0.002 Å and 0.1° for distances and angles, respectively, the structure parameters of oxazole are as follows:0(1)-C(2) = 1.357C(2)-N(3) = 1.291N(3)-C(4) = 1.395C(4)-C(5) = 1.352C(5)-O(1) = 1.369C(2)-H(2) = 1.075C(4)-H(4) = 1.075C(5)-H(5) = 1.073The geometry of oxazole is compared with that of isoxazole and with the structures of the closely related compounds furan and 1,3,4-oxadiazole.

The Scent of Maibowle – π Electron Localization in Coumarin from Its Microwave‐Determined Structure

“…With all atoms located on the ab-plane, we expected an inertial defect very close to zero, as observed for e.g. pyrrole (0.017 uÅ 2 ) [36], oxazole (0.056 uÅ 2 ) [37], 2TPC (0.008 uÅ 2 ) [28], and fluorobenzene (0.033 uÅ 2 ), but surprisingly found c = Ic -Ia -Ib = -0.294 uÅ 2 . Such negative, large values have been observed for many molecules related to coumarin such as the PAHs [3] and PANHs [4] mentioned in Section 2, as well as 9cyanoanthracene [38], quinolone [19], and isoquinoline [19], which could be traced back to significant out-of-plane vibrations of the rings [39].…”

Unraveling the protonation site of oxazole and solvation with hydrophobic ligands by infrared photodissociation spectroscopy

“…2 and Table S1 in the ESI †). 38,44 Protonation of Ox may occur at any of the aromatic ring atoms, and their structures are shown in Fig. 3 and Fig.…”

“…[32][33][34][35][36] The geometric and spectroscopic properties of the planar Ox molecule have extensively been studied in its neutral S 0 state ( 1 A 0 ). [37][38][39][40][41][42][43][44][45][46] However, no experimental information is available for any neutral Ox-L n clusters, probably because the broad absorption spectrum prevents the application of convenient size-selective resonant ionization techniques. 47,48 Photoelectron spectra of Ox reveal that ionization into the planar ground electronic state ( 2 A 00 ) occurs by removal of an electron from a bonding p-orbital localized on the C4-C5 and O1-C2-N3 bonds.…”

14N Nuclear quadrupole coupling and methyl internal rotation in the microwave spectrum of 2-methylpyrrole

“…In the case of the non-methylated systems inertial defects of 0.017, 0.074, 0.056, and 0.076 uÅ 2 are found for pyrrole(1) [26], thiazole (2)[27], oxazole (3)[28], and isothiazole (4) [29], respectively. The deviation from zero can be explained by the zero point vibrations of the rings.…”