On the existence of intramolecular hydrogen bonds in methyl o-mercaptobenzoate and 2-methoxymethylbenzenethiol

1981 ◽  
Vol 59 (3) ◽  
pp. 566-571 ◽  
Author(s):  
Ted Schaefer ◽  
David M. McKinnon ◽  
Rudy Sebastian ◽  
Bert Krawchuk
Keyword(s):  
Sulfhydryl Group ◽  
Intramolecular Hydrogen Bonding ◽  
Carbonyl Oxygen ◽  
Spectral Parameters ◽  
H Nmr ◽  
Conformational Freedom ◽  
Text Interaction ◽  
Intramolecular Hydrogen ◽  
Cis And Trans ◽  
Infrared Data

Full analyses of the 1H nmr spectra of methyl o-mercaptobenzoate and of 2-methoxymethylbenzenethiol yield spectral parameters suggesting that the trans conformer of the former is preferred by 1.6 ± 0.7 kJ/mol in free energy in solution at 305 K. Both cis and trans conformers can be reasonably discussed in terms of "planar" conformations. The ether displays nearly equal concentrations of cis and trans conformers. However, these conformers display considerable conformational freedom of the sulfhydryl group. These results are compared to previous infrared data. It is suggested that in the ester the small tendency towards intramolecular hydrogen bonding involves the carbonyl oxygen. Any [Formula: see text] interaction in the ether must surely occur for conformations in which the S—H and C—O bonds are far from the ring plane.

Photoelectron studies on intramolecularly hydrogen-bonded systems. I. The photoelectron spectra of cis- and trans-2-aminocyclopentanol, and cis- and trans-2-(N,N-dimethylamino)cyclopentanol

1976 ◽  
Vol 54 (4) ◽  
pp. 642-646 ◽  
Author(s):  
R. S. Brown
Keyword(s):  
Hydrogen Bonding ◽  
Ionization Energy ◽  
Lone Pair ◽  
Intramolecular Hydrogen Bonding ◽  
Photoelectron Spectra ◽  
Hydrogen Bonded Systems ◽  
Intramolecular Hydrogen ◽  
Cis And Trans ◽  
Infrared Data ◽  
Hydrogen Bonded

The photoelectron spectra of cis- and trans-2-aminocyclopentanol and cis- and trans-2-(N,N,-dimethylamino)cyclopentanol have been recorded and interpreted. The cis isomers exhibit N lone pair ionizations at higher ionization energy, and O lone pair ionizations at lower ionization energy than their trans isomers.The results are most consistent with the existence and observation of intramolecular hydrogen-bonding in the cis isomers. Infrared data on these systems also show that the cis isomers exist in the intramolecularly hydrogen-bonded state.

In-plane and out-of-plane conformational preferences of the sulfhydryl group in some halothiophenol derivatives

1979 ◽  
Vol 57 (12) ◽  
pp. 1421-1425 ◽  
Author(s):  
Ted Schaefer ◽  
William J. E. Parr
Keyword(s):  
Sulfhydryl Group ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Group ◽  
Recent Analysis ◽  
Phenol Derivatives ◽  
Out Of Plane ◽  
Intramolecular Hydrogen ◽  
Cis And Trans ◽  
Spin Spin Coupling

Long-range spin–spin coupling constants between sulfhydryl protons and ring protons in some halothiophenol derivatives in CCl4 solutions are reported. In contrast to the corresponding phenol derivatives, substantial amounts of out-of-plane conformers are present at 305 K for all but 2,6-dichlorothiophenol. The cis and trans conformers differ by only about 0.2 kcal/mol in free energy for 2,4-dibromothiophenol and 2,4-dichlorothiophenol, in good agreement with a recent analysis of the dipole moment observed for the latter compound. The barrier to internal rotation of the sulfhydryl group is considerably smaller than for a hydroxyl group and rough estimates are given for the barrier in a few compounds. For example, the barrier in 2,3,5,6-tetrafluorothiophenol is lower than in 2,6-dichlorothiophenol. STO-3G MO calculations overestimate the internal barrier to rotation of the sulfhydryl group, but yield charge densities for this group which indicate that a major cause of the relative weakness of its intramolecular hydrogen bonds resides in its lack of polarity.

β-Amino ketoximes: a study of basicity, hydrogen bonding and isomerism

1977 ◽  
Vol 30 (7) ◽  
pp. 1467 ◽  
Author(s):  
HK Powell ◽  
JM Russell
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Calorimetric Data ◽  
Amino Groups ◽  
Or Groups ◽  
Inductive Effects ◽  
Methylene Groups ◽  
Secondary Amino ◽  
Intramolecular Hydrogen ◽  
Cis And Trans

The protonation reactions of the diamine dioxime 4,4,9,9-tetramethyl- 5,8-diazadodecane-2,11-dione dioxime and its O-methyl and bis-O-methyl ethers have been studied at 25�, I 0.10 M NaCl. The (substituted) oxime groups cause a marked reduction in the basicity of the secondary amino groups. log K (potentiometric) and ΔH (calorimetric) data are interpreted in terms of inductive effects of the oxime group and possible intramolecular hydrogen bonding, N+-H...N(OR)=, pKa for methoxy-amine, NH2OMe, has been determined (4.62�0.01, I 0.10 M NaCl, 25�). ������ P.m.r. spectra are assigned for β-amino ketoximes having α- methyl and α-methylene groups cis and trans to =N-OR groups. Infrared spectra are reported.

Application of photoelectron spectroscopy to intramolecularly hydrogen-bonded systems. Part III. The photoelectron spectra of cis and trans 2-substituted cyclopentanols and cis and trans 2-substituted cyclohexanols

1976 ◽  
Vol 54 (12) ◽  
pp. 1929-1937 ◽  
Author(s):  
R. S. Brown
Keyword(s):  
Hydrogen Bonding ◽  
Photoelectron Spectroscopy ◽  
Intramolecular Hydrogen Bonding ◽  
Photoelectron Spectra ◽  
Molecular Orbital Calculations ◽  
Cis And Trans Isomers ◽  
Koopmans Theorem ◽  
Hydrogen Bonded Systems ◽  
Intramolecular Hydrogen ◽  
Cis And Trans

The photoelectron spectra of several well defined molecules exhibiting intramolecular hydrogen bonding has been determined and the analysis of the spectra is in accord with recent molecular orbital calculations of related systems. The experimentally determined enthalpies of the hydrogen bonds in cis-2-aminocyclopentanol and cis- and trans-2-aminocyclohexanol do not correlate in any simple fashion with the shifts in the ionization energies of the nO and nN orbitals compared to a model which precludes hydrogen bonding. The spectral differences attributed to hydrogen bonding in the cis and trans 2-substituted cyclanols cannot be attributed to differences in the through-bond interaction of the n orbitals on either atom since the cis and trans isomers of 1,2-dimethoxycyclopentane and 1,2-dimethoxycyclohexane show virtually identical pe spectra. A discussion of the applicability of Koopmans' theorem and the effect of the hydrogen bond in both the ion and ground states is presented.

The planar conformation of 2-methylthiobenzaldehyde in solution

1983 ◽  
Vol 61 (1) ◽  
pp. 26-28
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian
Keyword(s):  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spectral Parameters ◽  
H Nmr ◽  
Heavy Atoms ◽  
Planar Conformation ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Infrared Data

The 1H nmr spectral parameters are extracted for a 4 mol% solution of 2-methylthiobenzaldehyde in CCl4 at 305 K. The long-range spin–spin coupling constants involving the aldehydic and methyl protons are consistent only with a preferred conformation in which all heavy atoms are coplanar, as are the chemical shifts of the ring and methyl protons. This conclusion contradicts previous interpretations of the dipole moment, the nmr parameters, and of the infrared data for CCl4 solutions. The present data show that the O-syn and O-anti forms of the compound are present in roughly equal proportions.

scholarly journals Multicentered hydrogen bonding in 1-[(1-deoxy-β-D-fructopyranos-1-yl)azaniumyl]cyclopentanecarboxylate (`D-fructose-cycloleucine')

2019 ◽  
Vol 75 (8) ◽  
pp. 1096-1101 ◽  
Author(s):  
Valeri V. Mossine ◽  
Charles L. Barnes ◽  
Thomas P. Mawhinney
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Side Chain ◽  
Slow Rotation ◽  
H Nmr ◽  
Compound C ◽  
Nmr Data ◽  
Cyclopentane Ring ◽  
Intramolecular Hydrogen ◽  
Hydroxy Groups

The title compound, C12H21NO7, (I), is conformationally unstable; the predominant form present in its solution is the β-pyranose form (74.3%), followed by the β- and α-furanoses (12.1 and 10.2%, respectively), α-pyranose (3.4%), and traces of the acyclic carbohydrate tautomer. In the crystalline state, the carbohydrate part of (I) adopts the 2 C 5 β-pyranose conformation, and the amino acid portion exists as a zwitterion, with the side chain cyclopentane ring assuming the E 9 envelope conformation. All heteroatoms are involved in hydrogen bonding that forms a system of antiparallel infinite chains of fused R 3 3(6) and R 3 3(8) rings. The molecule features extensive intramolecular hydrogen bonding, which is uniquely multicentered and involves the carboxylate, ammonium and carbohydrate hydroxy groups. In contrast, the contribution of intermolecular O...H/H...O contacts to the Hirshfeld surface is relatively low (38.4%), as compared to structures of other D-fructose-amino acids. The 1H NMR data suggest a slow rotation around the C1—C2 bond in (I), indicating that the intramolecular heteroatom contacts survive in aqueous solution of the molecule as well.

Synthesis and spectroscopic study of aminals derived from 8-aminoquinoline

1982 ◽  
Vol 60 (13) ◽  
pp. 1775-1779 ◽  
Author(s):  
Juana Bellanato ◽  
Enrique Galvez ◽  
Rosario Escobar ◽  
Jose Manuel Cano-Pavon
Keyword(s):  
Hydrogen Bonding ◽  
Schiff Base ◽  
Spectroscopic Study ◽  
Mass Spectra ◽  
Intramolecular Hydrogen Bonding ◽  
H Nmr ◽  
Intramolecular Hydrogen

Treating 8-aminoquinoline with di-2-pyridyl ketone, pyridine-2-carboxaldehyde, or 6-methylpyridine-2-carboxaldehyde leads to the formation of the corresponding aminal instead of the expected Schiff base. The ir, 1H nmr, and mass spectra of these compounds are described and discussed.Infrared and 1H nmr analyses indicate that these aminals enjoy intramolecular hydrogen bonding. This effect is considered to contribute significantly to their unusual stability.

Intramolecular Hydrogen Bonding of vic-Diols in Cyclic Systems. II.1OH...O and OH... π-Electron Bonding in cis- and trans-1,2-Diaryl-1,2-acenaphthenediols2

1959 ◽  
Vol 81 (24) ◽  
pp. 6472-6477 ◽  
Author(s):  
Emil J. Moriconi ◽  
William F. O'Connor ◽  
Lester P. Kuhn ◽  
Elizabeth A. Keneally ◽  
Frederick T. Wallenberger
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Cyclic Systems ◽  
Intramolecular Hydrogen ◽  
Cis And Trans ◽  
In Cis

Conformational consequences of intramolecular hydrogen bonding by OH to the directional lone-pair of sulfur in derivatives of methyl phenyl sulfide, diphenyl sulfide, and diphenyl disulfide

1982 ◽  
Vol 60 (3) ◽  
pp. 342-348 ◽  
Author(s):  
Ted Schaefer ◽  
Salman R. Salman ◽  
Timothy A. Wildman ◽  
Peter D. Clark
Keyword(s):  
Lone Pair ◽  
Phenyl Group ◽  
Intramolecular Hydrogen Bonding ◽  
Spectral Parameters ◽  
Phenyl Sulfide ◽  
Methyl Phenyl Sulfide ◽  
Twist Conformation ◽  
Diphenyl Disulfide ◽  
Conformational Determinant ◽  
Intramolecular Hydrogen

Complete spectral parameters for the 1H nmr spectra of 2-hydroxyphenyl methyl sulfide, 2, 2-hydroxyphenyl phenyl sulfide, 3, bis(2-hydroxy-3-tert-butyl-5-methylphenyl) sulfide, 4, and bis(2-hydroxyphenyl) disulfide, 5, are reported for CCl4 solutions at 305 K. For 2 the parameters are consistent only with a conformation in which the C—S—C plane is roughly perpendicular to the aromatic plane. The conformational determinant is the [Formula: see text] hydrogen bond which forces the mainly 3p orbital on sulfur into the benzene plane. In 3 a similar arrangement is found about the sulfur atom, with the phenyl group lying in the C—S—C plane and therefore perpendicular to the hydroxyphenyl plane (skew conformation). In 4 two [Formula: see text] hydrogen bonds exist, yielding a gable (twist) conformation. Compound 5 exists in the axial conformation with probable C2 symmetry, the CSSC dihedral angle and the CCSS torsion angles all being near 90°. For none of the compounds is there any evidence for [Formula: see text] interactions.

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