Quantitative model of solvent effects on hydroxypyridine-pyridone and mercaptopyridine-thiopyridone equilibriums: correlation with reaction-field and hydrogen-bonding effects

The preparation and proton resonance spectra of the 1-iodopropenes are reported and solvent effects on the proton spectra of the chloro-, bromo-, and iodo-compounds are measured. The proton coupling constants are discussed in terms of old and new electronegativity correlations. The olefinic cis and trans proton shifts can be attributed mainly to a paramagnetic contribution from the substituent, whereas the gem olefinic proton shifts depend in addition on the electron-withdrawing power of the substituent. The methyl proton shifts in the 1-substituted compound show little dependence on the substituent and this is discussed in relation to the barrier heights to methyl rotation. The solvent shifts in benzene cannot be completely reconciled with a dipole – induced dipole model. They increase with the size of the substituent and are largest for protons farthest from the substituent. The solvent shifts in acetone can be explained as due to weak hydrogen bonding and reaction field effects. The shifts of protons gem to the substituent arise mainly from hydrogen bonding, whereas the shifts of protons cis or trans have significant contributions from both effects. The reaction field effects can also account for the methyl shifts in acetone.

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Solvent and temperature effects on the tautomerization of a carbonitrile molecule: A conductor-like polarizable continuum model (CPCM) study

Main Group Chemistry ◽

10.3233/mgc-210016 ◽

2021 ◽

Vol 20 (1) ◽

pp. 59-68

Author(s):

Zohreh Khanjari ◽

Bita Mohtat ◽

Reza Ghiasi ◽

Hoorieh Djahaniani ◽

Farahnaz Kargar Behbahani

Keyword(s):

Gas Phase ◽

Solvent Effects ◽

Continuum Model ◽

Solvent Polarity ◽

Polarizable Continuum Model ◽

Dielectric Constants ◽

Frontier Orbitals ◽

Reaction Field ◽

Polarizable Continuum ◽

Homo Lumo

This research examined the effects of solvent polarity and temperature on the tautomerization of a carbonitrile molecule at CAM-B3LYP/6-311G (d,p) level of theory. The selected solvents were n-hexane, diethyl ether, pyridine, ethanol, methanol, and water. The solvent effects were examined by the self-consistent reaction field theory (SCRF) based on conductor-like polarizable continuum model (CPCM). The solvent effects were explored on the energy barrier, frontier orbitals energies, and HOMO-LUMO gap. Dependencies of thermodynamic parameters (ΔG and ΔH) on the dielectric constants of solvents were also tested. Specifically, the temperature dependencies of the thermodynamics parameters were studied within 100–1000 K range. The rate constant of the tautomerism reaction was computed from 300 to 1200 K, in the gas phase.

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STRUCTURAL AND SOLVENT EFFECTS ON THE n → π*(′U ← ′A) TRANSITIONS IN ALIPHATIC CARBONYL DERIVATIVES: EVIDENCE FOR HYPERCONJUGATION IN THE ELECTRONICALLY EXCITED STATES OF MOLECULES

Canadian Journal of Chemistry ◽

10.1139/v60-340 ◽

1960 ◽

Vol 38 (12) ◽

pp. 2508-2513 ◽

Cited By ~ 26

Author(s):

C. N. R. Rao ◽

G. K. Goldman ◽

A. Balasubramanian

Keyword(s):

Hydrogen Bonding ◽

Carbonyl Group ◽

Excited States ◽

Solvent Effects ◽

Electronically Excited States ◽

Carbonyl Derivatives ◽

Alkyl Groups ◽

Electronically Excited

The n → π* transition of the carbonyl group has been studied in solvents of varying degree of polarity and hydrogen-bonding ability, in a number of aliphatic carbonyl derivatives. Evidence for hyperconjugation of the alkyl groups in the electronically excited states of molecules has been presented.

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Solvent Effects on the Hydrogen Bonding of N-Phenylurethane

The Journal of the Society of Chemical Industry Japan ◽

10.1246/nikkashi1898.72.11_2430 ◽

1969 ◽

Vol 72 (11) ◽

pp. 2430-2436 ◽

Cited By ~ 3

Author(s):

Takehide TANAKA ◽

Tetsuo YOKOYAMA ◽

Yukio YAMAGUCHI ◽

Seikou NAGANUMA

Keyword(s):

Hydrogen Bonding ◽

Solvent Effects

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Solvent Effects and Hydrogen Bonding

High Resolution NMR ◽

10.1016/b978-0-12-084660-3.50017-3 ◽

1980 ◽

pp. 253-258

Author(s):

EDWIN D. BECKER

Keyword(s):

Hydrogen Bonding ◽

Solvent Effects

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Selective deshielding of aromatic protons in some ortho-substituted acetanilides

Canadian Journal of Chemistry ◽

10.1139/v68-422 ◽

1968 ◽

Vol 46 (15) ◽

pp. 2593-2600 ◽

Cited By ~ 18

Author(s):

James R. Bartels-Keith ◽

Ronald F. W. Cieciuch

Keyword(s):

Hydrogen Bonding ◽

Magnetic Resonance ◽

Solvent Effects ◽

Proton Magnetic Resonance ◽

Aromatic Proton ◽

Intramolecular Hydrogen Bonding ◽

Low Field ◽

Intramolecular Hydrogen

Certain ortho-substituted acetanilides exhibit proton magnetic resonance signals at unusually low field for the amido proton and the aromatic proton adjacent to the acetamido group. This effect, explicable in terms of intramolecular hydrogen-bonding, has been observed for nitro, carbonyl, sulfamoyl, and sulfonyl substituents. Solvent effects are discussed.

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