VIBRATIONAL ANALYSIS, CONFORMATIONAL STABILITY, FORCE CONSTANTS, INTERNAL ROTATION BARRIERS, MP2=FULL AND DFT CALCULATIONS OF 1,3-DIMETHYLURACIL TAUTOMERS

1 3-dimethyluracil normal coordinate analysis vibrational frequencies ab initio calculation internal rotation barriers.

СТРУКТУРНАЯ ОБУСЛОВЛЕННОСТЬ ФРАГМЕНТАЦИИ МОЛЕКУЛ НАФТЛЛИНСУЛЬФОНИЛГАЛОГЕНИДОВ И НАФТАЛИНСУЛЬФОНАМИДОВ ПРИ ИОНИЗАЦИИ ЭЛЕКТРОНАМИ, ПЕГОКСИНИТРИТ В СОСТАВЕ ГЕММА, ...

The molecular structure of 1,3-dimcthyluracil (С6Н8N2O2; 1,3-DMU) is studied theoretically and experimentally using Gaussian 98 calculations and different spectroscopic techniques. <...> The vibrational spectrum for 1,3-DMU in the solid phase is recorded in the IR range 4000-400 cm '. <...> Initially, in order to get the most stable structure, twelve structures were proposed for the titled compound as a result of the internal rotation of CH3 around С—N bonds and kcto-cnol tautomcrism. <...> The single point energy and frequency calculations arc obtained by MP2 (Full) and DFT/B3LYP methods with the 6-3lG(d) basis set using the Gaussian 98 computation package. <...> After the complete relaxation of twelve isolated isomers, the (diketo) tautomcr was the only favored structure owing to its low energy relative to the other isomers and the prediction of real frequencies. <...> This interpretation is supported by the recorded infrared spectrum that shows the presence of only the diketo tautomer. <...> Aided by the normal coordinate analysis and potential energy distributions, a confident vibrational assignment of the fundamental frequencies is calculated. <...> The results are discussed herein and compared with similar molecules whenever possible. ! <...> The molecular structure of 1,3-dimcthyluracil (С6Н8N2O2; 1,3-DMU) is studied theoretically and experimentally using Gaussian 98 calculations and different spectroscopic techniques. <...> The vibrational spectrum for 1,3-DMU in the solid phase is recorded in the IR range 4000-400 cm '. <...> Initially, in order to get the most stable structure, twelve structures were proposed for the titled compound as a result of the internal rotation of CH3 around С—N bonds and kcto-cnol tautomcrism. <...> The single point energy and frequency calculations arc obtained by MP2 (Full) and DFT/B3LYP methods with the 6-3lG(d) basis set using the Gaussian 98 computation package. <...> After the complete relaxation of twelve isolated isomers, the (diketo) tautomcr was the only favored structure owing to its low energy relative to the other isomers and the prediction of real frequencies. <...> This interpretation is supported by the recorded infrared spectrum that shows the presence of only the diketo tautomer. <...> Aided by the normal coordinate analysis and potential energy distributions, a confident vibrational assignment of the fundamental frequencies is calculated. <...> The results are discussed herein and compared with similar molecules whenever possible. ! <...>

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