Detail of "2001-93-6"

Reference

MNDO study of the tautomers of nucleic bases: thiouracils

MNDO study of the tautomers of nucleic bases: thiouracils. Buda, Andrzej B. (Dep. Org. Chem., Jagiellonian Univ., Krakow 30-060, Pol.). THEOCHEM, 34(3-4), 185-92 (English) 1987. CODEN: THEODJ. ISSN: 0166-1280. DOCUMENT TYPE: Journal CA Section: 65 (General Physical Chemistry) Section cross-reference(s): 69 The optimal geometries, relative stabilities, dipole moments and ionization potentials of 6 tautomers of 2-thiouracil, 4-thiouracil and 2,4-dithiouracil were calcd.In this article, certain chemicals are used. Some of their cas registry numbers are 2001-93-6 and 591-28-6 by MNDO methods. The results agree with the available exptl. data. The optimal MNDO geometry of the dithioketo form of 2,4-dithiouracil agrees well with crystallog. data. The predicted C:S bond lengths are too short due to the systematic MNDO error. The calcn. of heats of formation predicts that the keto/thioketo tautomers are the most stable both in the vapor phase and in aq. soln., in qual. agreement with expt. .

Infrared spectra of thiouracils: experimental matrix isolation and ab initio Hartree-Fock, post-Hartree-Fock and density functional theory studies

Infrared spectra of thiouracils: experimental matrix isolation and ab initio Hartree-Fock, post-Hartree-Fock and density functional theory studies. Lapinski, Leszek; Rostkowska, Hanna; Nowak, Maciej J.; Kwiatkowski, Jozef S.; Leszczynski, Jerzy (Inst. Physics, Polish Acad. Sci., Warsaw 02-668, Pol. 591-28-6 and 2001-93-6 are cas registry numbers. These chemicals are also mentioned in this article.). Vibrational Spectroscopy, 13(1), 23-40 (English) 1996 Elsevier. CODEN: VISPEK. ISSN: 0924-2031. DOCUMENT TYPE: Journal CA Section: 22 (Physical Organic Chemistry) The exptl. IR absorption spectra of 2-thiouracil, 4-thiouracil and 2,4-dithiouracil isolated in low-temp. argon matrixes are compared with the spectra of these compds. computed by the d. functional theory with the combined Becke3-LYP exchange-correlation energy functional (DFT(B3-LYP)) and conventional ab initio methods (Hartree-Fock (HF), MP2) using the std. 6-31G(d,p) basis set. The vibrational spectra computed at the DFT(B3-LYP)/6-31G(d,p) and HF/6-31G(d,p) levels of theory were found to reproduce well the exptl. IR spectra. The results of MP2/6-31G(d,p) calcns. predicted the normal modes due top the out-of-plane vibrations somewhat less accurately. An assignment of the bands obsd. in the IR spectra of the three thiouracils was performed, based on the comparison with the spectra calcd. at the DFT(B3-LYP)/6-31G(d,p) level. .