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.

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.

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.

Nonbonded and interactions in 2-(4-chlorophenylthio) benzaldehyde in solution. An average skew conformation

1992 ◽  
Vol 70 (9) ◽  
pp. 2375-2380 ◽  
Author(s):  
Ted Schaefer ◽  
Lina B.-L. Lee ◽  
Rudy Sebastian
Keyword(s):  
Title Compound ◽  
Chemical Shifts ◽  
Minimum Energy ◽  
Lone Pair ◽  
Phenyl Group ◽  
Coupling Constants ◽  
Spectral Parameters ◽  
Text Interaction ◽  
The One

The 1H nuclear magnetic resonance spectral parameters are reported for 4.0 mol% solutions of 2-(4-chlorophenylthio) benzaldehyde in CS2/C6D12 and acetone-d6 at 300 K. In CS2 the O-syn conformer is 36% abundant, rising to 50% in acetone-d6. These abundances are compared to those of the O-syn and O-trans conformers of 2-(alkylthio) benzaldehydes in CCl4, solution. On the basis of coupling constants and chemical shifts it is concluded that the skew conformer of the title compound is very likely the one of minimum energy in both solutions. In the skew conformer the plane of the 4-chlorophenyl group lies perpendicular to the CSC plane and also to that of the other aromatic moiety. It is suggested that the [Formula: see text] interaction is rather weak and that the population of the O-syn conformer is controlled by the orientation of the mainly 3p lone-pair orbital on sulfur. At best, the [Formula: see text] interaction is attractive only when the 3p orbital lies perpendicular to the plane of the formyl group. The skew conformation of the title compound is contrasted to the skew conformation of 2-hydroxyphenyl phenyl sulfide in which, however, the role of the two aromatic planes is reversed; the 3p orbital now lies in or near the plane of the phenyl group COH due to an attractive [Formula: see text] interaction.

Electronic spectrum of bibenzimidazole homologue: effects of solvents and acid concentration

1989 ◽  
Vol 67 (7) ◽  
pp. 1200-1205 ◽  
Author(s):  
Awadesh Kumar ◽  
Hemant K. Sinha ◽  
Sneh K. Dogra
Keyword(s):  
Spectral Characteristics ◽  
Solvent Molecule ◽  
Lone Pair ◽  
Direct Interaction ◽  
Blue Shift ◽  
Intramolecular Hydrogen Bonding ◽  
Wavelength Absorption ◽  
Nitrogen Lone Pair ◽  
Intramolecular Hydrogen ◽  
Different Characteristics

The absorption and fluorescence spectra of bibenzimidazole (BBI), N, N′-dimethylbibenzimidazole (MBBI), and methylene, 2,2′-bibenzimidazole (MtBBI) have been recorded in six solvents of different characteristics and at various acid concentrations. This study indicates the presence of intramolecular hydrogen bonding in BBI in both S0 and S1 states, leading to large conjugation of two benzimidazole (BI) rings. The geometry of BBI is the same in the S0 and S1 states. The spectral characteristics of BBI are insensitive to the solvents. The interaction of solvent molecule attached to the nitrogen lone pair and methyl group rotates the benzimidazolyl ring in MBBI around the single bond. This leads to a blue shift in the long wavelength absorption band maximum and a decrease in the intensity of this band. The two MBI rings are coplanar in the S1 state. Presence of methylene group inhibits the direct interaction between the BI groups and these rings behave almost independently, i.e., the spectral characteristics of this molecule nearly resemble those of benzimidazole. Keywords: absorption spectrum, fluorescence spectrum, pKa, bibenzimidazoles, excited state pKa.

Spectroscopic and electrochemical properties of intramolecularly hydrogen-bonded compounds. Ortho-hydroxyazobenzenes

1981 ◽  
Vol 59 (5) ◽  
pp. 821-827 ◽  
Author(s):  
Salvatore Millefiori ◽  
Arcangelo Millefiori
Keyword(s):  
Bond Formation ◽  
Substituent Effects ◽  
Lone Pair ◽  
Intramolecular Hydrogen Bonding ◽  
Photoelectron Spectra ◽  
Polarographic Reduction ◽  
Reduction Potentials ◽  
Half Wave ◽  
Experimental Findings ◽  
Intramolecular Hydrogen

The gas-phase uv photoelectron spectra and the half-wave polarographic reduction potentials in acetonitrile solutions of a series of 2-hydroxy-5-methylazobenzene have been determined. The first three IP's and the E1/2 values were linearly correlated with σ+ and σ constants, respectively. E1/2 can also be linearly related to the energy of the lowest unoccupied molecular orbital. Effects of the intramolecular hydrogen bonding on the pe spectra and on the polarographic reduction of the title compounds were evaluated by comparing the experimental findings in 2-hydroxy-5-methylazobenzene, 2-methoxy-5-methylazobenzene, and p-hydroxyazobenzene. On H-bond formation, the antibonding combination of the two nitrogen lone-pairs, n−, and the oxygen lone-pair is ionized at a slightly higher energy and at a lower energy, respectively, than in the non H-bonded compound. The first π-ionization band is slightly lowered in energy in the non H-bonded structure, probably owing to a normal substituent effect. These features are not maintained in the 4'-nitro derivative, where the band encompassing the n− ionization remains at the same potential in both structures, while the first π band in the non H-bonded compound moves toward higher IP. Spectral differences between the bonded and nonbonded structures are the result of a balance of substituent effects, and of both hydrogen bond and orbital interactions. The solution electron affinity of the studied compounds increases on H-bond formation by an amount comparable with the experimental strength of the H-bonding. INDO/S-CI calculations are in qualitative agreement with the experimental results.

THE VIBRATIONAL MECHANISM OF THE FUNDAMENTAL NH2 STRETCHING VIBRATIONS IN ANILINES

1962 ◽  
Vol 40 (12) ◽  
pp. 2300-2316 ◽  
Author(s):  
Peter J. Krueger
Keyword(s):  
Lone Pair ◽  
Intramolecular Hydrogen Bonding ◽  
Electronic Effects ◽  
Substituted Anilines ◽  
Tetrahedral Configuration ◽  
Nitrogen Lone Pair ◽  
Resultant Increase ◽  
Stretching Vibrations ◽  
Integrated Intensities ◽  
Intramolecular Hydrogen

The integrated intensities, frequencies, and half-band widths of the fundamental symmetric and asymmetric NH2 stretching vibrations in 33 ortho-substituted anilines, measured in dilute carbon tetrachloride solution, have been examined in relation to the corresponding absorption band parameters for 31 meta- and para-substituted anilines, taking into consideration the electronic effects of the substituents. From an almost tetrahedral configuration in p-phenylenediamine, the calculated s-character of the nitrogen atom gradually increases as the substituent groups become more electron withdrawing, with a resultant increase in the apparent HNH angle and the NH force constant. Ortho substitution in general leads to enhanced HNH angle opening, probably because of intramolecular hydrogen bonding. The decrease in half-band width for both vibrational modes in ortho-substituted anilines with respect to corresponding values in meta and para compounds is ascribed to steric hindrance to solvation of the amino group.The asymmetric intensities in ortho-substituted anilines are generally increased over corresponding values in meta and para compounds, unlike the behavior of the symmetric mode. These results are consistent with a vibrational mechanism taking into account the following factors for each mode: (i) the direction of the transition moment, (ii) the extent of nitrogen lone pair and aromatic π-electron participation, and (iii) the direct field effect of the ortho substituent.

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