1983
DOI: 10.1039/p29830000345
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Infrared and 1H nuclear magnetic resonance studies of hydrogen bonds in some pyridine trifluoroacetates and their deuteriated analogues in dichloromethane

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Cited by 27 publications
(13 citation statements)
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“…The almost identical chemical shifts observed for hydrogen bonds formed to these acceptors (Figure 6) indicate that di- ortho -halo substitution per se does not perturb the length of a hydrogen bond or prevent it from shortening. These results are consistent with previous solution studies of intermolecular hydrogen bond formation between trifluoroacetic acid and substituted pyridines88 in which di- ortho- and non- ortho -substituted pyridines fell on the same trend line of 1 H chemical shift versus p K a . This identical behavior between di- ortho and non- ortho -substituted hydrogen bond acceptors presumably reflects their ability to rotate in solution to avoid unfavorable interactions between the ortho substituents and the hydrogen bond donor.…”
Section: Resultssupporting
confidence: 92%
“…The almost identical chemical shifts observed for hydrogen bonds formed to these acceptors (Figure 6) indicate that di- ortho -halo substitution per se does not perturb the length of a hydrogen bond or prevent it from shortening. These results are consistent with previous solution studies of intermolecular hydrogen bond formation between trifluoroacetic acid and substituted pyridines88 in which di- ortho- and non- ortho -substituted pyridines fell on the same trend line of 1 H chemical shift versus p K a . This identical behavior between di- ortho and non- ortho -substituted hydrogen bond acceptors presumably reflects their ability to rotate in solution to avoid unfavorable interactions between the ortho substituents and the hydrogen bond donor.…”
Section: Resultssupporting
confidence: 92%
“…These minima can be represented by a tautomeric equilibrium involving the hydrogen-bonded complex (HBC), OH...N, and the ion-pair proton transfer complex (FTC), 0-. . .H+N (Scheme 1) (20)(21)(22)(23)(24)(25). The continuum absorption in the middle region of the IR spectra of the HN-TFE mixtures supports the existence of the proposed tautomeric HBC G PTC equilibrium.…”
Section: Discussionmentioning
confidence: 60%
“…The loss of conjugation will increase the pK a to a value slightly lower than the 9.5 that is typical of tertiary alkylamines, slightly lower because of the nitrogen being bonded to an sp 2 -hybridized carbon and two methyl groups rather than the three sp 3 hybridized carbons in tertiary alkylamines. 5 The observed pK a is significantly higher, 12.1, and this higher value must be explained by the relief of electronic repulsion by intramolecular hydrogen bonding in the protonated diamine. The pK a value of 12.1. indicates significantly greater stabilization of protonated 8 through internal hydrogen bonding than of protonated 9 by hydrogen bonds to water.…”
Section: The Basicities Of Proton Spongesmentioning
confidence: 93%
“…Moderately strong hydrogen bonds display deuterium isotope effects on infrared stretching frequencies, the downfield NMR chemical shifts, and low H 2 O/D 2 O fractionation factors (3). In addition, the carbonyl stretching frequencies for species like CuO----H-O are decreased by hydrogen bonding, and the magnitude of this effect is regarded as a measure of the strength of the interaction (5,6).…”
Section: Characterization Of Strong Hydrogen Bondsmentioning
confidence: 98%