FT-IR spectroscopic study of uracil derivatives and their hydrogen-bonded complexes with model proton donors. Part 6. Proton transfer in uracil. HCl complexes isolated in concentrated or strongly annealed argon matrices

Graindourze, M; Smets, Johan; Zeegers‐Huyskens, Th.; Maes, Guido

doi:10.1016/0022-2860(93)07902-9

Cited by 7 publications

(3 citation statements)

References 26 publications

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“…These bands can be interpreted as the shifted HCl stretching modes in the CO···H- -Cl and N···H- -Cl complexes, respectively. The location of these typical ν s bands suggests H-bonds of the intermediate I → II type, which is similar to the results earlier obtained for the uracil/HCl/Ar system. , A further argument in favor of this assignment is the proton affinity value of the 2OP tautomer (898 kJ·mol -1 ), which is close to the proton affinity of uracil (870 kJ·mol -1 ). Other characteristic bands for the CO···H- -Cl complex are the decrease of the ν(CO) mode (−46 cm -1 ), the increase of the out-of-plane γ(CO) mode (+14 cm -1 ), and the frequency decrease of the ν(NH) mode by 14 cm -1 .…”

Section: Resultssupporting

confidence: 88%

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Matrix-Isolation FT-IR Studies and Theoretical Calculations of Different Types of Hydrogen-Bonding: 2-Hydroxypyridine/2-Oxopyridine Complexed with HCl

et al. 1999

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The H-bond interaction of the cytosine model compound 2-hydroxypyridine and its tautomer 2-oxopyridine with HCl is investigated using the combined matrix-isolation FT-IR and theoretical density functional and ab initio methods. The theoretical calculations have been carried out at the B3-LYP/6-31++G** and RHF/6-31++G** levels of theory. Different types of hydrogen-bonding have been found: two closed complexes of the proton transfer type, each containing two hydrogen bonds, i.e., N+H···Cl-···HO and CO+ H···Cl-···HN; two open complexes of intermediate strength, N···H- -Cl and CO···H- -Cl; and one weak complex, HO···HCl. The theoretical results indicate that the closed H-bonded complexes are the most stable systems for both the hydroxy and the oxo tautomers. The increased stability of these complexes is due to a cooperative H-bonding effect. The experimental spectra are consistent with this prediction, but the weaker complexes are also identified. A comparison of the experimental and calculated IR frequencies demonstrates that the frequency shifts of the vibrational modes directly involved in the H-bond interactions, especially the X−H stretching modes, are better predicted by the DFT method than by the RHF method. For the other vibrational modes not directly involved in the H-bonds, the RHF methodology has a similar accuracy compared to the DFT method.

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Section: Resultssupporting

confidence: 88%

“…In our formerly published results for complexes of different bases with HCl in Ar matrices, − the complexes appeared to be of type II and intermediate type I → II. Furthermore, it was observed that these systems give rise to proton transfer at higher HCl concentration or after the matrix samples are annealed.…”

Section: Introductionmentioning

confidence: 80%

Matrix-Isolation FT-IR Studies and Theoretical Calculations of Different Types of Hydrogen-Bonding: 2-Hydroxypyridine/2-Oxopyridine Complexed with HCl

et al. 1999

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“…The calculations and experimental data are in agreement, within experimental error. B3LYP/6-31ϩG* therefore appears to be a reasonable method and level at which to calculate gas-phase enthalpies of deprotonation of nucleobases [1,2,14,81,[83][84][85].…”

Section: Discussionmentioning

confidence: 99%

The acidity of uracil and uracil analogs in the gas phase: Four surprisingly acidic sites and biological implications

Kurinovich

Lee

2002

J. Am. Soc. Mass Spectrom.

160

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The gas phase acidities of a series of uracil derivatives (1-methyluracil, 3-methyluracil, 6-methyluracil, 5,6-dimethyluracil, and 1,3-dimethyluracil) have been bracketed to provide an understanding of the intrinsic reactivity of uracil. The experiments indicate that in the gas phase, uracil has four sites more acidic than water. Among the uracil analogs, the N1-H sites have ⌬H acid values of 331-333 kcal mol Ϫ1 ; the acidity of the N3 sites fall between 347-352 kcal mol Ϫ1 . The vinylic C6 in 1-methyluracil and 3-methyluracil brackets to 363 kcal mol Ϫ1 , and 369 kcal mol Ϫ1 in 1,3-dimethyluracil; the C5 of 1,3-dimethyluracil brackets to 384 kcal mol Ϫ1 . Calculations conducted at B3LYP/6-31ϩG* are in agreement with the experimental values. The bracketing of several of these sites involved utilization of an FTMS protocol to measure the less acidic site in a molecule that has more than one acidic site, establishing the generality of this method. In molecules with multiple acidic sites, only the two most acidic sites were bracketable, which is attributable to a kinetic effect. The measured acidities are in direct contrast to in solution, where the two most acidic sites of uracil (N1 and N3) are indifferentiable. The vinylic C6 site is also particularly acidic, compared to acrolein and pyridine. The biological implications of these results, particularly with respect to enzymes for which uracil is a substrate, are discussed. (J Am Soc Mass Spectrom 2002, 13, 985-995)

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ChemInform Abstract: FT‐IR Spectroscopic Study of Uracil Derivatives and Their Hydrogen‐ Bonded Complexes with Model Proton Donors. Part 6. Proton Transfer in Uracil. HCl Complexes Isolated in Concentrated or Strongly Annealed Argon Matrices.

et al. 1994

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FT-IR spectroscopic study of uracil derivatives and their hydrogen-bonded complexes with model proton donors. Part 6. Proton transfer in uracil. HCl complexes isolated in concentrated or strongly annealed argon matrices

Cited by 7 publications

References 26 publications

Matrix-Isolation FT-IR Studies and Theoretical Calculations of Different Types of Hydrogen-Bonding: 2-Hydroxypyridine/2-Oxopyridine Complexed with HCl

Matrix-Isolation FT-IR Studies and Theoretical Calculations of Different Types of Hydrogen-Bonding: 2-Hydroxypyridine/2-Oxopyridine Complexed with HCl

The acidity of uracil and uracil analogs in the gas phase: Four surprisingly acidic sites and biological implications

ChemInform Abstract: FT‐IR Spectroscopic Study of Uracil Derivatives and Their Hydrogen‐ Bonded Complexes with Model Proton Donors. Part 6. Proton Transfer in Uracil. HCl Complexes Isolated in Concentrated or Strongly Annealed Argon Matrices.

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