Chain association equilibriums. Nuclear magnetic resonance study of the hydrogen bonding of N-monosubstituted amines. III. In dioxane

Graham, Laurine L.; Chang, Chang Y.

doi:10.1021/j100676a010

Cited by 21 publications

(9 citation statements)

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“…Since the absorbance for pure N -methylacetamide was too large to carry out experiments in the neat liquid, we recorded the FT-IR spectra of solutions of NMA. Carbon tetrachloride was chosen as the solvent since it interacts only very weakly with NMA and similar compounds. , In contrast to hydrogen-bonding solvents such as dioxane and water, CCl 4 does not disrupt intermolecular amide−amide hydrogen bonding. − For neat NMA, a low-resolution IR spectrum is available in the Merck FT-IR atlas. Here one observes IR stretch frequencies for both hydrogen-bonded and terminal NH groups in neat, liquid NMA…”

Section: Resultsmentioning

confidence: 99%

“…66,67 In contrast to hydrogen-bonding solvents such as dioxane and water, CCl 4 does not disrupt intermolecular amide-amide hydrogen bonding. [68][69][70] For neat a For comparison with the experimental vibration spectra as well as for the use in the QCE model all frequencies are scaled by a factor of 0.89. The average values for each cluster are obtained by weighting the frequencies with the appropriate calculated absorbance A. NMA, a low-resolution IR spectrum is available in the Merck FT-IR atlas.…”

Section: Resultsmentioning

confidence: 99%

“…66,67 In contrast to hydrogen-bonding solvents such as dioxane and water, CCl 4 does not disrupt intermolecular amide-amide hydrogen bonding. [68][69][70] For neat Harmonic Frequencies ν j in cm -1 for N-H, CdO, and C-N NMA, a low-resolution IR spectrum is available in the Merck FT-IR atlas. Here one observes IR stretch frequencies for both hydrogen-bonded and terminal NH groups in neat, liquid NMA.…”

Section: Experimental Ir Frequenciesmentioning

confidence: 99%

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Quantum Cluster Equilibrium Theory of Liquids: Temperature Dependence of Hydrogen Bonding in LiquidN-Methylacetamide Studied by IR Spectra

Ludwig¹,

Reis²,

Winter³

et al. 1998

J. Phys. Chem. B

111

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Temperature-dependent infrared spectra for liquid N-methylacetamide are calculated by the ab initio quantum cluster equilibrium (QCE) and Gaussian-94 methods and compared with experimental measurements. The calculations are based on standard ab initio self-consistent-field (SCF) methods at the 3-21G levels for five different molecular clusters. The cluster sizes vary from the monomer up to a five-membered linear structure. Strong cooperative effects are found in the molecular clusters and are reflected in the geometries and vibrational spectra for each species. The equilibrium populations of the clusters were calculated for the entire liquid range. At low temperatures the linear pentamer is the dominant species. At higher temperatures these clusters are replaced, primarily, by linear dimers and monomers. The calculated frequencies are in excellent agreement with the temperature behavior found in FT-IR experiments.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Experimental Ir Frequenciesmentioning

confidence: 99%

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Quantum Cluster Equilibrium Theory of Liquids: Temperature Dependence of Hydrogen Bonding in LiquidN-Methylacetamide Studied by IR Spectra

Ludwig¹,

Reis²,

Winter³

et al. 1998

J. Phys. Chem. B

111

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“…4, using the values of d bond d free , X B and X A . The d bond d free value is available from references (25,26). X B and X A values are also available from the mean aggregation number, <n>, for L-LVA in 1,2-dichloroethane.…”

Section: Chiral Aggregates Of L-lva In 12-mentioning

confidence: 99%

“…Consequently, we can evaluate X A and X B by assuming n value and using the <n> value at an arbitrary total concentration. Graham and Chang (25,26) reported that the difference in chemical shift, d bond d free , for N-monosubstituted amide in CCl 4 is 2.4-2.8 ppm and that in 1,4-dioxane is 0.79-1.42 ppm, respectively. For L-LVA in relatively non-polar 1,2-dichloroethane, we assumed therefore 2.0 ppm for the d bond d free value.…”

Section: (9)mentioning

confidence: 99%

Solvent Effect on Chiral Aggregate Formation of Acylamino Acids.

et al. 2002

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We studied formation of chiral aggregates of optical active N-lauroyl-L-valine (L-LVA), N-lauroyl-L-glutamic acid (L-LGA) and methylester of L-LVA (L-LVMe) in various solvents such as acetonitrile, 1,4-dioxane, tetrahydrofuran and 1,2-dichloroethane through the measurements of circular dichroism (CD), NMR chemical shift of N-H proton and vaporpressure osmometry (VPO). The above acylamino acids and L-LVMe showed CD bands at 212-215 nm, whose intensities depended on temperature. The CD bands have been believed to come from the formation of chiral aggregates. However, by means of NMR and VPO analyses, the acylamino acids and L-LVMe were found to be present mostly as monomers in relatively polar solvents such as acetonitrile, 1,4-dioxane and tetrahydrofuran. On the other hand, L-LVA in 1,2dichloroethane forms chiral aggregates; the mean aggregation number of L-LVA increases with increasing in its concentration.

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Study of hydrogen bonding interactions relevant to biomolecular structure and function

1992

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A h initio molecular orbital calculations were used to study hydrogen bonding interactions and interatomic distances of a number of hydrogen bonded complexes that are germane to biomolecular structure and function. The calculations were carried out at the STO-3G, 3-21G, 6-31G*, and MP2/6-31G* levels (geometries were fully optimized at each level). For anionic species, 6-31 + G* and MP2/6-31+ G* were also used. In some cases, more sophisticated calculations were also carried out. Whenever possible, the corresponding enthalpy, entropy, and free energy of complexation were calculated. The agreement with the limited quantity of experimental data is good. For comparison, we also carried out semiempirical molecular orbital calculations. In general, AM1 and PM3 give lower interaction enthalpies than the best ah initio results. With regard to structural results, AM1 tends to favor bifurcated structures for 0-H-0 and N-HO types of hydrogen bonds, but not for hydrogen bonds involving 0-H-S and S-H-0, where the usual hydrogen bond patterns are observed. Overall, AM1 geometries are in general in poor agreement with ab initio structural results. On the other hand, PM3 gives geometries similar to the ab initio ones. Hence, from the structural point of view PM3 does show some improvement over AMl. Finally, insights into the formation of cyclic or open formate-water hydrogen bonded complexes are presented.

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Chain association equilibriums. Nuclear magnetic resonance study of the hydrogen bonding of N-monosubstituted amines. III. In dioxane

Cited by 21 publications

References 0 publications

Quantum Cluster Equilibrium Theory of Liquids: Temperature Dependence of Hydrogen Bonding in LiquidN-Methylacetamide Studied by IR Spectra

Quantum Cluster Equilibrium Theory of Liquids: Temperature Dependence of Hydrogen Bonding in LiquidN-Methylacetamide Studied by IR Spectra

Solvent Effect on Chiral Aggregate Formation of Acylamino Acids.

Study of hydrogen bonding interactions relevant to biomolecular structure and function

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