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.

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.

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.

2-Substituted and 2,6-disubstituted 1,4-benzoquinone 4-oximes ('p-nitrosophenols')

1969 ◽  
Vol 22 (5) ◽  
pp. 935 ◽  
Author(s):  
RK Norris ◽  
S Sternhell
Keyword(s):  
Hydrogen Bonding ◽  
Physical Properties ◽  
Intramolecular Hydrogen Bonding ◽  
Tautomeric Equilibrium ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Electronic Effects ◽  
Intramolecular Hydrogen

The preparation and physical properties of 27 compounds in the title series are described. Tautomerism, syn-anti isomerism, N.M.R. parameters, and the mechanism of isomerization are discussed. In this series of derivatives, the tautomeric equilibrium in dioxan solutions lies heavily towards the oxime form unless intramolecular hydrogen bonding between the substituent at C2 (or C6) and the phenolic hydroxyl group of the nitroso form is possible. The substituents at C2 (and C6) influence the position of the syn-anti equilibrium in the quinone monoxime forms through electronic effects.

Aromatic amides. V. Intramolecular hydrogen bonding in ortho-substituted anilides

1970 ◽  
Vol 23 (8) ◽  
pp. 1667 ◽  
Author(s):  
JM Appleton ◽  
BD Andrews ◽  
ID Rae ◽  
BE Reichert
Keyword(s):  
Hydrogen Bonding ◽  
Molecular Geometry ◽  
Intramolecular Hydrogen Bonding ◽  
Amide Group ◽  
Amide Proton ◽  
Substituted Anilines ◽  
Real Value ◽  
Intramolecular Hydrogen ◽  
Acyl Derivatives ◽  
Ortho Substituent

The proton magnetic resonance spectra of deuterochloroform solutions of a number of ortho-substituted anilines and their S-acyl derivatives have been measured. Variations in the acylation shifts of the ring protons are explained in terms of intramolecular hydrogen bonding between the amide proton and the ortho-substituent. Calculations of the contribution made to the acylation shifts by the anisotropy of the amide group were found to be too sensitive to the molecular geometry to be of any real value. Acylation shifts for a series of 4'-substituted 2'-nitroacetanilides correlate well with the σp values of the 4'-substituents.

The assessment of intramolecular hydrogen bonding in ortho-substituted anilines by an NMR method

2020 ◽  
Vol 315 ◽  
pp. 113730
Author(s):  
Michael H. Abraham ◽  
Raymond J. Abraham ◽  
Amin Aghamohammadi ◽  
Kamyar Afarinkia ◽  
Xiangli Liu
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Substituted Anilines ◽  
Nmr Method ◽  
Intramolecular Hydrogen

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.

DOUBLE-MINIMUM POTENTIAL FOR INTRAMOLECULARLY HYDROGEN-BONDED PROTONS IN ORTHO-SUBSTITUTED ANILINES

1964 ◽  
Vol 42 (2) ◽  
pp. 201-211 ◽  
Author(s):  
P. J. Krueger
Keyword(s):  
Hydrogen Bonding ◽  
Vibrational Level ◽  
Fundamental Mode ◽  
Intramolecular Hydrogen Bonding ◽  
Antisymmetric Mode ◽  
Substituted Anilines ◽  
Minimum Potential ◽  
Intramolecular Hydrogen ◽  
Ortho Substituent ◽  
Hydrogen Bonded

The concentration and temperature-independent splitting of the first overtone NH2 symmetric stretching band in 31 ortho-substituted anilines in which intramolecular hydrogen bonding is possible is interpreted in terms of a double-minimum potential for the hydrogen bonded proton. The intensity ratio of the doublet and the extent of the splitting is related to the basicity of the ortho-substituent, modified by the rigid geometrical restrictions of the intramolecular system. The absence of band splitting in the corresponding fundamental mode suggests that the secondary minimum lies in the vicinity of the v = 2 vibrational level. The antisymmetric mode appears to be less sensitive to perturbations.Deuteration studies, the spectra of some o-substituted N-methyl anilines, and the first over-tone bands of N-methyl aniline in very basic solvents support these views.

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