Infrared study of some 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids: Correlation with MO-calculations

The IR spectra of a series of 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids (substituent = OH, SH, CH3, CH3S and NH2) were studied from the aspect of the influence of the subsitutent on the polarizability of some bonds, keto-enol tautomerism and hydrogen bond formation. The spectra were taken using solids due to the low solubility of the acids. Theoretical calculations were done using the MNDO-AM1 semiempirical molecular-orbital method. The stabilities of various tautomers were calculated simulating the dielectric continuum using the COSMO facility of the MOPAC program package. Theoretical calculations were made for all the possible tautomers of the 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids. For the most stable isomers, the vibrational spectra were calculated. For the majority of the compounds the most stable isomer was identified having the structure 2-Y-6-oxo-4-carboxy-3H-pyrimidine. Besides this structure, for the 2-amino-, and 2-methyl- derivatives the zwitterionic forms have very similar stability. The 2-hydroxy compound is most stable as the 2,6-dioxo-1H, 3H isomer. The calculated vibrations for the compounds with a single stable structure correlate very well with the experimental frequencies. For the 2-methyl- and 2-amino- compounds the correlation is considerably less satisfactory. The most probable reason for this deviation is the existence of two or more tautomets in equilibrium. The correlation of the measured frequencies and the pKa values of the acids, indicate that the same tautomers exist in the solid state and in the solution.

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Hydration of Simple Carboxylic Acids from Infrared Spectra of HDO and Theoretical Calculations

The Journal of Physical Chemistry B ◽

10.1021/jp200748u ◽

2011 ◽

Vol 115 (16) ◽

pp. 4834-4842 ◽

Cited By ~ 15

Author(s):

Maciej Śmiechowski ◽

Emilia Gojło ◽

Janusz Stangret

Keyword(s):

Carboxylic Acids ◽

Infrared Spectra ◽

Theoretical Calculations

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pH Behavior of Polymer Complexes between Poly(carboxylic acids) and Poly(acrylamide derivatives) Using a Fluorescence Label Technique

Polymers ◽

10.3390/polym11071196 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1196 ◽

Cited By ~ 1

Author(s):

Yuriko Matsumura ◽

Kaoru Iwai

Keyword(s):

Hydrogen Bond ◽

Carboxylic Acids ◽

Interpolymer Complex ◽

Interpolymer Complexes ◽

Hydrogen Bond Formation ◽

Label Technique ◽

Fluorescence Label ◽

Subsequent Decrease ◽

Mixed Systems ◽

Poly Acrylamide

In order to clarify the local environment during interpolymer complex formation between poly(carboxylic acids) and poly(acrylamide derivatives) with different N-substitutions, a fluorescence label technique was used. 3-(2-propenyl)-9-(4-N,N-dimethylaminophenyl) phenanthrene (VDP) was used as an intramolecular fluorescence probe. All polymers were synthesized by free radical polymerization. Interpolymer complexation was monitored by charge transfer emission from the VDP unit. Both of the poly(carboxylic acids) formed interpolymer complexes with poly(N,N-dimethylacrylamide) (polyDMAM). The micro-environments around the VDP unit in the acidic pH region for the poly(methacrylic acid) (polyMAAc) and polyDMAM mixed systems were more hydrophobic than those of the poly(acrylic acid) (polyAAc) and polyDMAM mixed systems, as the α-methyl group of the MAAc unit contributed to hydrophobicity around the polymer chain during hydrogen bond formation. This suggests that, when the poly(carboxylic acids) and poly(acrylamide derivatives) were mixed, with a subsequent decrease in the solution pH, a hydrogen bond was partially formed, following which the hydrophobicity of the micro-environment around the polymer chains was changed, resulting in the formation of interpolymer complexes. Moreover, the electron-donating ability of the carbonyl group in the poly(acrylamide derivatives) had an effect on complexation with poly(carboxylic acids).

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An infrared study of the interaction between ethyl N-(diphenylmethylene)glycinate with proton donors: comparison with N-benzylidenemethylamine

Canadian Journal of Chemistry ◽

10.1139/v86-378 ◽

1986 ◽

Vol 64 (12) ◽

pp. 2305-2309 ◽

Cited By ~ 6

Author(s):

Marleen Ruysen ◽

Thérèse Zeegers-Huyskens

Keyword(s):

Hydrogen Bond ◽

Ir Spectra ◽

Equilibrium Constants ◽

Lone Pair ◽

Imino Group ◽

Infrared Study ◽

Hydrogen Bond Formation ◽

Hydroxy Proton ◽

Proton Donors ◽

Intramolecular Hydrogen

The interaction between ethyl N-(diphenylmethylene)glycinate (DPG) and hydroxy proton donors or pyrrole has been investigated by ir spectrometry. The equilibrium constants, enthalpies, and entropies of complex formation have been determined in carbon tetrachloride solution and compared with the data obtained for the complexes involving N-benzylidene-methylamine and the same proton donors. The ir spectra studied mainly in the νOH, νC=N, νC=O, and νC—O regions suggest that hydrogen bond formation occurs at the N atom of the imino group and at the O atom of the carbonyl group. The results are discussed in terms of the basicity at the two acceptor sites and of the accessibility of the lone pair of electrons. The ir spectra of the solid adduct of DPG with HCl show that protonation takes place on the N atom. The protonated structure is possibly stabilized by an intramolecular hydrogen bond.

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Amino acid/zwitterion equilibria II: vibrational and NMR studies of substituted thiazolidine-4-carboxylic acids

Canadian Journal of Chemistry ◽

10.1139/v91-252 ◽

1991 ◽

Vol 69 (11) ◽

pp. 1721-1727 ◽

Cited By ~ 4

Author(s):

H. E. Howard-Lock ◽

C. J. L. Lock ◽

M. L. Martins

Keyword(s):

Nuclear Magnetic Resonance ◽

Amino Acid ◽

Carboxylic Acids ◽

Infrared And Raman Spectra ◽

Solid Samples ◽

Nmr Studies ◽

Nuclear Magnetic Resonance Spectra ◽

Key Words Amino Acid ◽

Methyl Derivatives ◽

Derivatives Of

Infrared and Raman spectra (4000–100 cm) of solid samples of seven different 2-phenyl-, N-benzoyl-, and 2-ethyl-2 methyl derivatives of L-cysteine and D-penicillamine have been observed and assigned. Proton and 13C nuclear magnetic resonance spectra for the compounds have also been measured. Amino acid/zwitterion equilibria are discussed with reference to pK values and the vibrational spectra. Key words: amino acid/zwitterion equilibria, thiazolidine carboxylic acids.

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Theoretical study of point defects in GaN and AlN; lattice relaxations and pressure effects

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s1092578300001447 ◽

1997 ◽

Vol 2 ◽

Cited By ~ 13

Author(s):

I. Gorczyca ◽

A. Svane ◽

N. E. Christensen

Keyword(s):

Theoretical Calculations ◽

Pressure Effects ◽

Function Technique ◽

Orbital Method ◽

Full Potential ◽

Cation Site ◽

Carbon Impurity ◽

Atomic Displacements ◽

Cubic Gan ◽

Linear Muffin Tin Orbital

Native defects and some common dopants (Mg, Zn, and C) in cubic GaN and AlN are examined by means of ab initio theoretical calculations using two methods: i) the Green's function technique based on the linear muffin-tin orbital method in the atomic-spheres approximation; ii) a supercell approach in connection with the full-potential linear muffin-tin-orbital method. We apply the first method to look mainly at the energetic positions of the defect and impurity states in different charge states and their dependence on hydrostatic pressure. The second method allows us to study lattice relaxations. Whereas small relaxations are found near vacancies and substitutional Mg and Zn, the calculations predict large atomic displacements around antisite defects and the substitutional carbon impurity on the cation site.

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An infrared study of selective hydrogenation of carboxylic acids to corresponding aldehydes over a ZrO2 catalyst: pivalic acid to 2,2-dimethylpropanal

Catalysis Letters ◽

10.1007/bf00766153 ◽

1993 ◽

Vol 17 (3-4) ◽

pp. 309-317 ◽

Cited By ~ 12

Author(s):

Nan Ding ◽

Junko Kondo ◽

Ken ichi Maruya ◽

Kazunari Domen ◽

Toshiharu Yokoyama ◽

...

Keyword(s):

Carboxylic Acids ◽

Selective Hydrogenation ◽

Pivalic Acid ◽

Infrared Study ◽

Zro2 Catalyst

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Theoretical studies of model compounds of lathyrane-type diterpenes

Canadian Journal of Chemistry ◽

10.1139/v03-171 ◽

2004 ◽

Vol 82 (1) ◽

pp. 11-18 ◽

Cited By ~ 1

Author(s):

Yukimasa Terada ◽

Tomoo Matsuura ◽

Yukari Mori ◽

Shosuke Yamamura

Keyword(s):

Ab Initio ◽

Molecular Mechanics ◽

Molecular Orbital ◽

Theoretical Calculations ◽

Membered Ring ◽

Orbital Method ◽

Methyl Groups ◽

Molecular Orbital Method ◽

Stable Conformation ◽

Semi Empirical

The conformation of the 11-membered ring of the lathyrane skeleton has been investigated using NMR spectra and theoretical calculations. Some other skeletons, such as jatrophane, jatrapholane, and tigliane, seem to be derived from this framework, and the conformation is important in connection with the configuration of the resultant diterpenes. The conformation of lathyrane is principally defined by the orientation of the two methyl groups; namely, the methyl groups on C1 and C6 directed above or below the ring plane. Theoretical calculations revealed that the predominant conformation is altered depending on the oxygen functional groups on the ring. As far as the bond lengths, bond angles, and dihedral angles are concerned, all calculation methods afforded reasonable results. In contrast, as regards conformational stability, only the ab initio molecular orbital method (RHF/6-31G*) predicted the most stable conformation, consistent with NOE experiments. On the other hand, the stable conformations predicted by the ab initio method (RHF/STO-3G), the semi-empirical molecular orbital method (MOPAC(PM3)), and the molecular mechanics calculations (MM3) did not necessarily agree with the conformers suggested by the NOE experiments.Key words: ab initio MO, semi-empirical MO, molecular mechanics, 11-membered ring conformation, NOE.

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Photochemical reactions of azo compounds. X. Photochemical properties of azobenzene-2-carboxylic acids

Australian Journal of Chemistry ◽

10.1071/ch9670929 ◽

1967 ◽

Vol 20 (5) ◽

pp. 929 ◽

Cited By ~ 2

Author(s):

CP Joshua ◽

GE Lewis

Keyword(s):

Hydrogen Bonding ◽

Carboxylic Acid ◽

Carboxylic Acids ◽

Intramolecular Hydrogen Bonding ◽

Photochemical Reactions ◽

Azo Compounds ◽

Neutral Compounds ◽

Methyl Derivatives ◽

Intramolecular Hydrogen ◽

Derivatives Of

Two chloro and two methyl derivatives of azobenzene-2-carboxylic acid have been found to yield the corresponding derivatives of benzo[c]cinnoline-4- carboxylic acid in good yields when irradiated in 98% sulphuric acid. The question of intramolecular hydrogen bonding in relation to the properties of azobenzene-2-carboxylic acids is discussed. Infrared absorption spectra of the neutral compounds have provided confirmation of internal hydrogen bonding. Attempts to prepare the cis isomers of these azo compounds have been unsuccessful.

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