Microwave Spectrum and Conformational Composition of 1-Vinylimidazole

Abstract

The microwave spectrum of 1-vinylimidazole has been investigated in the 21-80 GHz spectral region. The spectra of two conformers have been assigned. One of these forms is planar, while the other is nonplanar with the imidazole ring and the vinyl group forming an angle of 15(4)° from coplanarity. The planar form is found to be 5.7(7) kJ/mol more stable than the nonplanar rotamer by relative intensity measurements. The spectra of 10 vibrationally excited states of the planar form and one excited-state spectrum of the nonplanar form were assigned. The vibrational frequencies of several of these states were determined by relative intensity measurements. The microwave work has been augmented by quantum chemical calculations at the CCSD/cc-pVTZ, MP2/cc-pVTZ, and B3LYP/cc-pVTZ levels of theory. The B3LYP calculations predict erroneously that both forms of 1-vinylimidazole are planar, whereas the MP2 and CCSD calculations correctly predict the existence of a planar and a nonplanar conformer of this compound.

Microwave spectrum, structure, tautomeric, and conformational composition of 4-vinylimidazole

“…As mentioned previously, a thorough microwave spectroscopic structural investigation of 1-vinylimidazole and associated quantum chemical calculations has been published recently. 3 Two conformers, here designated (i) and (ii), are possible. As illustrated in Figure 5, the shapes and atom dispositions are reminiscent of those of isomers IV and II of 4-vinylimidazole, respectively, differing only in the interchange of C with N between the ring vinyl junction and an adjacent ring atom.…”

“…Gas phase microwave spectroscopy has been reported for unsubstituted imidazole 1 and the substituted variants histamine 2 and 1vinylimidazole. 3 In general, imidazole compounds occurring in biology follow histidine in having ring substituents at the 4-position carbon.…”

Cadmium(II) Chloride Complex Containing 1-Vinylimidazole Ligand: Structural, Spectroscopic and Thermal Properties

“…Imidazole and its derivatives have become an important part of many pharmacological activities such as, analgesic, anti-inflammatory (Suzuki et al, 1992), anti-anthelmintic (Lunt et al, 1987), anti-fungal (Johnson et al, 1999), antitubercular (Pandey et al, 2009), antimicrobial (Vijesh et al, 2013), anticancer (Miyachi et al, 1998) and cardiovascular (Erhardt et al, 1989) activities. Except their pharmacological effects, they also function as catalysts (Jencks, 1970) and polymerizing agents (Samdal and Møllendal, 2011) for example 1vinylimidazole (vim) ( Figure 1) is used as a copolymerization agent in the production of cationic polymers (Ebel et al, 2000). Imidazole and its derivatives are actively used in the synthesis of various coordination compounds.…”

Rotational spectra and nuclear quadrupole coupling constants of 4- and 2-iodoimidazole

“…[8][9][10][11][12] Imidazole-containing compounds including histamine and histidine have also been studied by microwave spectroscopy. [13][14][15][16][17] Each of 4iodoimidazole and 2-iodoimidazole has been used extensively as a synthetic reagent since their first syntheses in 1928 and 1977 respectively. [18][19][20][21][22] It will be shown that 4-iodoimidazole and 2iodoimidazole can each be prepared for spectroscopic study by a method that combines laser vaporisation of the solid precursor with cooling by subsequent supersonic co-expansion with argon.…”