Anharmonicity, solvent effects, and hydrogen bonding: NH stretching vibrations

1970 ◽  
Vol 48 (14) ◽  
pp. 2197-2203 ◽  
Author(s):  
A. Foldes ◽  
C. Sandorfy
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Solvent Effects ◽  
Bond Formation ◽  
Hydrogen Bond Formation ◽  
Stretching Vibration ◽  
Solvent Shifts ◽  
Stretching Vibrations ◽  
Secondary Amides ◽  
Influence Of Solvent

The influence of solvent effects and hydrogen bond formation on the anharmonicity of the NH stretching vibration of simple secondary amides, lactams, anilides, indole, pyrrole, and imidazole have been studied; and the frequencies of the first and second overtones, their half widths and solvent shifts measured. The validity of Buckingham's theory is established in the case of inert solvents; whereas the second order perturbation treatments are shown to be inapplicable to the case of hydrogen bonding solvents. All NH stretching modes seem to exhibit the same anharmonic behavior which is very different from that of OH vibrations.

A Low Temperature Infrared Study of Hydrogen Bonding in N-Alkylacetamides

1973 ◽  
Vol 51 (21) ◽  
pp. 3640-3646 ◽  
Author(s):  
Marie-Claude Bernard-Houplain ◽  
C. Sandorfy
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Low Temperature ◽  
Infrared Spectra ◽  
Bond Formation ◽  
Coupling Constant ◽  
Infrared Study ◽  
Hydrogen Bond Formation ◽  
Stretching Vibration ◽  
Secondary Amides

The infrared spectra of N-methylacetamide and two other secondary amides were measured in solution at temperatures ranging from 22 to −190 °C in both the fundamental and the overtone regions. At least two hydrogen bonded species are found as association increases with decreasing temperature. The effect of hydrogen bond formation on the anharmonicity of the NH stretching vibration and on the NH stretching – NH bending coupling constant is examined.

Enthalpies of hydrogen bond formation of 1-octanol with aprotic organic solvents. A comparison of the solvation enthalpy, pure base, and non-hydrogen-bonding baseline methods

1985 ◽  
Vol 63 (2) ◽  
pp. 342-348 ◽  
Author(s):  
W. Kirk Stephenson ◽  
Richard Fuchs
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Bond Formation ◽  
Enthalpies Of Solution ◽  
Dispersion Interactions ◽  
Butyl Ether ◽  
Hydrogen Bond Formation ◽  
Solvation Enthalpy ◽  
Benzene Toluene ◽  
Good Agreement

Enthalpies of solution (ΔHs) of 1-octanol and five model compounds (di-n-butyl ether, n-heptyl methyl ether, 1-fluoro-octane, 1-chlorooctane, and n-octane) have been determined in 13 solvents (heptane, cyclohexane, CCl4, 1,1,1-trichloro-ethane, 1,2-dichloroethane, triethylamine, butyl ether, ethyl acetate, DMF, DMSO, benzene, toluene, mesitylene), and combined with heats of vaporization to give enthalpies of transfer from vapor to solvent (ΔH(v → S)). These values have been used to calculate the enthalpy of hydrogen bond formation (ΔHh) of 1-octanol with each solvent, using the pure base (PB), solvation enthalpy (SE), and non-hydrogen-bonding baseline (NHBB) methods. Evidence is presented suggesting that (a) the SE method is susceptible to mismatches of the 1-octanol vs. model polar and dispersion interactions, (b) the PB method is sensitive to polar interaction mismatches, whereas (c) the NHBB method compensates for both polar and dispersion interactions mismatches. The (apparent) ΔHh values determined by the SE and PB methods may be as much as several kcal/mol (nearly 50%) too large, because of the inclusion of other polar and dispersion interactions. The NHBB method is therefore preferred for determining enthalpies of H-bond formation from calorimetric data. However, apparent ΔHh values from the SE and PB methods can be incorporated into total solvatochromic equations using Taft–Kamiet π*, β, and ξ parameters, to provide enthalpies of H-bond formation in good agreement with ΔHh (NHBB).

Hydrogen bonding of n-alcohols of different chain lengths

1985 ◽  
Vol 63 (1) ◽  
pp. 40-45 ◽  
Author(s):  
Lucie Wilson ◽  
R. Bicca de Alencastro ◽  
C. Sandorfy
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Chain Length ◽  
Bond Formation ◽  
Hydrocarbon Chain ◽  
Hydrogen Bond Formation ◽  
Degree Of Association ◽  
Chain Lengths ◽  
Anesthetic Potency

The anesthetic potency of n-alcohols exhibits a somewhat irregular dependence on the length of the hydrocarbon chain. An attempt has therefore been made to ascertain if this is related to the relative tendency for hydrogen bond formation by these alcohols. No such relationship was found. The result was rather that the degree of association by hydrogen bond formation of dissolved alcohols appears to be independent of the chain length, that is of the extent of other interactions that exist in these solutions.

Solvent effects on hydrogen-bond formation

1985 ◽  
Vol 89 (10) ◽  
pp. 1888-1891 ◽  
Author(s):  
J. N. Spencer ◽  
C. L. Campanella ◽  
E. M. Harris ◽  
W. S. Wolbach
Keyword(s):  
Hydrogen Bond ◽  
Solvent Effects ◽  
Bond Formation ◽  
Hydrogen Bond Formation

A nuclear magnetic resonance study of hydrogen bonding of δ-valerolactam

1969 ◽  
Vol 47 (19) ◽  
pp. 3655-3660 ◽  
Author(s):  
J. M. Purcell ◽  
H. Susi ◽  
J. R. Cavanaugh
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Bond Formation ◽  
Resonance Spectroscopy ◽  
Hydrogen Bond Formation ◽  
Wide Range ◽  
Nuclear Magnetic

The association of amide groups of δ-valerolactam through hydrogen bonding has been investigated by means of high resolution nuclear magnetic resonance spectroscopy in CCl4 and CDCl3 solutions. Chemical shifts of the NH proton signal were measured over a wide range of temperatures and concentrations. Thermodynamic properties associated with the [Formula: see text] hydrogen bond formation were evaluated from a least squares analysis by a direct search procedure with a digital computer. The obtained enthalpy values for hydrogen bond formation are in general agreement with results obtained by other methods.

N-Chlorination of secondary amides. II. Effects of substituents on rates of N-chlorination

1969 ◽  
Vol 47 (18) ◽  
pp. 3289-3297 ◽  
Author(s):  
E. W. C. W. Thomm ◽  
M. Wayman
Keyword(s):  
Hydrogen Bond ◽  
Oxygen Atom ◽  
Reaction Mechanisms ◽  
Bond Formation ◽  
Low Ph ◽  
Reverse Order ◽  
Primary Reaction ◽  
Hydrogen Bond Formation ◽  
Cl Atom ◽  
Secondary Amides

Various secondary amides have been N-chlorinated, at high and at low pH. The reactivity of the chlorinating reagents with all the amides investigated was found to have the sequence[Formula: see text]The substituent groups R1 and R2 of the amide [Formula: see text] were found to have large effects on the rate of chlorination. With the three molecular chlorinating agents, the reactivity of the amides was found to be in the order[Formula: see text]With hypochlorite ion the reverse order of reactivity was observed. These results are discussed and reaction mechanisms proposed. It is proposed that, when a hypochlorite ion is a chlorinating agent, the primary reaction is hydrogen bond formation between the amido hydrogen and the hypochlorite oxygen atom, but that the donation of electrons from the amido N to the Cl atom is the primary reaction with the molecular chlorinating agents.

Resonance-Induced Hydrogen Bonding at Sulfur Acceptors in R 1 R 2C=S and R 1CS2 − Systems

1997 ◽  
Vol 53 (4) ◽  
pp. 680-695 ◽  
Author(s):  
F. H. Allen ◽  
C. M. Bird ◽  
R. S. Rowland ◽  
P. R. Raithby
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Bond Formation ◽  
Lone Pair ◽  
Molecular Orbital Calculations ◽  
Hydrogen Bond Acceptor ◽  
Hydrogen Bond Formation ◽  
Coordination Numbers ◽  
Wide Range

The hydrogen-bond acceptor ability of sulfur in C=S systems has been investigated using crystallographic data retrieved from the Cambridge Structural Database and via ab initio molecular orbital calculations. The R1R2C=S bond lengths span a wide range, from 1.58 Å in pure thiones (R 1 = R 2 = Csp 3) to 1.75 Å in thioureido species (R 1 = R 2 = N) and in dithioates —CS^{-}_2. The frequency of hydrogen-bond formation at =S increases from 4.8% for C=S > 1.63 Å to more than 70% for C=S > 1.70 Å in uncharged species. The effective electronegativity of S is increased by conjugative interactions between C=S and the lone pairs of one or more N substituents (R 1 R 2): a clear example of resonance-induced hydrogen bonding. More than 80% of S in —CS^{-}_2 accept hydrogen bonds. C=S...H—N,O bonds are shown to be significantly weaker than their C=O...H—N,O analogues by (a) comparing mean S...H and O...H distances (taking account of the differing non-bonded sizes of S and O and using neutron-normalized H positions) and (b) comparing frequencies of hydrogen-bond formation in `competitive' environments, i.e. in structures containing both C=S and C=O acceptors. The directional properties and hydrogen-bond coordination numbers of C=S and C=O acceptors have also been compared. There is evidence for lone-pair directionality in both systems, but =S is more likely (17% of cases) than =O (4%) to accept more than two hydrogen bonds. Ab initio calculations of residual atomic charges and electrostatic potentials reinforce the crystallographic observations.

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