OH Frequency Research Articles

A comparative study of donor properties of sulphoxides and phosphine oxides in solvent extraction

A comparative study of the donor properties of sulphoxides and phosphine oxides in solvent extraction is reported. It was believed earlier that the stretching frequency of the phosphoryl group could serve as a measure of its basicity. In sulphoxides, however, the S → O frequency in different sulphoxides is nearly constant and cannot be a guide to their donor properties. A new method of assessing the relative donor strengths of both phosphine oxides and sulphoxides is described, based on the shift of the symmetric stretching frequency of OH of water on coordination with the donor. It is found that both phosphine oxides and sulphoxides form a single group, whose solvent extraction properties are determined by their relative donor strengths, as determined by this procedure. The extractions of water, perchloric acid, hydrochloric acid and pertechnic acid by dibutyl sulphoxide (DBSO) are reported. The extracted species are H 2O·2DBSO and H 2O·HClO 4.

Spectroscopic studies of hydrogen bonding: Hexafluoroisopropanol

The shifts of the OH stretching frequency and OH proton shielding constant of 1,1,1,3,3,3-hexafluoro-2-propanol upon hydrogen bond formation are reported. Oxygen, nitrogen, and sulfur donors of various types were used as Lewis electron pair donors. A correlation between the frequency and shielding constant changes is found and compared with those for phenol and 2,2,2-trifluoro-ethanol. The use of this data to index the acidities of these alcohols and the magnitides of the acid-base interactions is discussed. The influence of the substituent on the nature of chemical shift, frequency correlations is examined. The nonzero intercepts of the chemical shift, frequency shift correlations are discussed in terms of the generalized Lippincott-Schroeder one dimensional model for hydrogen bonded adducts, from which the importance of donor to hydrogen charge transfer is inferred. The data also appear to require a correction of about 0.5 ppm to the proton chemical shift when the donor atom is sulfur. The diethylsulfide, hexafluoro-2-propanol OH frequency shift appears to be anomolously low by about 75 cm −1 and results in a spectroscopic reversal of base strength.

Intramolecular Hydrogen Bonds. XIV. Correlation of the Hydroxyl and the Carbonyl Frequencies of Methyl Salicylates with Hammett’s Substituent Constants

Abstract The infrared OH and C=O stretching spectra of methyl 4- or 5-substituted salicylates have been measured in dilute carbon tetrachloride solutions, and the respective peak-frequencies have been correlated with ordinary Hammett’s σ-constants. The best linear relationship has been established between the γOH and the (σOH−0.38σCOOMe) values and between the γC=O and the (σCOOMe−0.49σOH) values, where σOH and σCOOMe are the σ-constants of a substituent with respect to the OH and the COOMe group respectively. Besides, in other internally-bonded phenol systems, including o-bromophenols, o,o′-dihalophenols, and salicylic acids, the plotting of the OH frequencies against the (σOH−AσX) values gave the best linear relationship, where A is a constant depending on the kind of proton acceptor, X. The value of A can be a measure of the electronic effects of the substituent, influencing the bonded OH frequency through X.

The effects of solvents on the hydrogen bonded OH stretching frequency

From measurements of the bonded OH frequencies of phenol—ether and π-base complexes in a range of solvents, it is deduced that the solvation to the hydrogen bonded system increases with the strength of the hydrogen bond. This result supports Bellamy's modified specific interaction theory of solvation [3]. A close correlation between the solvent constant G [1] and σ* X of the solvent HX was found, which suggests that the solvent effect on the hydrogen bonded system will be mainly due to lone-pair dipole the H-bond system-bond dipole (solvent) interaction. Temperature effects on the frequency of ν OH⋯B stretching absorption agree with the dipolar association theory, although not without some reservations.

Interferometric Study of Cosmic Line Emission at OH Frequencies

Interferometric observation of cosmic emission at OH frequency, noting emission source dimensions

The average XH stretching frequency as a measure of XH bond properties

The extent to which an XH stretching mode is decoupled from the rest of the vibrational modes in a molecule has been investigated quantitatively by means of second-order perturbation theory. The average of the XH frequencies from a set of equivalent XH bonds in a molecule can be shown to be an accurate measure of the XH force constant. Other bond properties such as internuclear distance and bond dissociation energy which are believed to be very nearly single-valued functions of the force constant are expected to correlate with the average XH frequency. Such correlations for the average frequencies of CH, NH and OH, groups in a variety of molecules have been made with bond distance and bond strength. It seems likely that the XH bond distance may be evaluated from vibrational frequencies with about the same over-all accuracy as from high resolution spectroscopic structure determinations. It is possible also to evaluate radical stabilization energies as well as XH bond dissociation energies from the average XH stretching frequency.

The average XH stretching frequency as a measure of XH bond properties

The extent to which an XH stretching mode is decoupled from the rest of the vibrational modes in a molecule has been investigated quantitatively by means of second-order perturbation theory. The average of the XH frequencies from a set of equivalent XH bonds in a molecule can be shown to be an accurate measure of the XH force constant. Other bond properties such as internuclear distance and bond dissociation energy which are believed to be very nearly single-valued functions of the force constant are expected to correlate with the average XH frequency. Such correlations for the average frequencies of CH, NH and OH, groups in a variety of molecules have been made with bond distance and bond strength. It seems likely that the XH bond distance may be evaluated from vibrational frequencies with about the same over-all accuracy as from high resolution spectroscopic structure determinations. It is possible also to evaluate radical stabilization energies as well as XH bond dissociation energies from the average XH stretching frequency.

Interpretation of the Infrared Spectra of the Solid Hydroxylammonium Halides

Infrared spectra of sublimed films of hydroxylammonium and deuterohydroxylammonium chlorides, bromides, and iodides have been obtained at 25°, —78°, and —180°C from 4000 to 400 cm—1. Satisfactory vibrational assignments for the hydroxylammonium ion can be made on the basis of an ionic model in which one end of the ion (H3NO) is axially summetric (C3v) and the other end (OH) is of Cs symmetry. A normal coordinate treatment based on a simplified valence force potential with ten constants reproduces 13 of the 18 frequencies of the hydroxylammonium and deuterohydroxylammonium ions to better than 2% and all 18 frequencies to better than 5%. The low NH and OH frequencies are believed to be due to the formal positive charge being distributed over all the atoms in the ion thereby weakening the covalently bonded H atoms and increasing the strengths of the electrostatic hydrogen bonds.

Studies on the Infrared Spectra of Heterocyclic Compounds. VII. Hydrogen-Bond Effect on Pyridine 1-Oxide and its Derivatives

Infrared investigations were made on the hydrogen-bond effect of pyridine 1-oxide and its derivatives with some proton donors. The assignment for N-O stretching frequency (strong absorption in the region of 1190 and 1320 cm-1) was further confirmed by observing the spectral change of N-oxide compounds following hydrogen-bond formation with methanol in non-polar solvent. The hydrogen-bonding ability of various derivatives was estimated in terms of the magnitude of shift in bonded OH frequency of methanol and an excellent linear relation was found by plotting these frequencies against the σ-values of the substituents. Anomalous behavior in 2-methyl derivatives was also pointed out and discussed. From a comparison of the frequency shift of the carbonyl stretching absorption in methanol and water, it was found that the electron-releasing ability of the N-oxide function towards 4-position of the ring is largely decreased in polar solvent with active hydrogen.

Hydrogen Bond Systems. Temperature Dependence of OH Frequency Shifts and OH Band Intensities

Hydrogen Bond Systems. Temperature Dependence of OH Frequency Shifts and OH Band Intensities

Hydrogen Bond Systems: Temperature Dependence of OH Frequency Shifts and OH Band Intensities

Hydrogen Bond Systems: Temperature Dependence of OH Frequency Shifts and OH Band Intensities

One-Dimensional Model of the Hydrogen Bond

A one-dimensional model for hydrogen bonding is proposed based on the potential function V = D[1—exp(—nΔr2/2r)]. The energy associated with both the weak and strong bonds of the configuration RO – H – – – OR2 is obtained through application of this function. A repulsive Van der Waals potential and an attractive electrostatic potential are also assumed to exist between the two electronegative atoms of the hydrogen bond. Through application of the conditions describing a stable equilibrium, relations are obtained which permit a calculation of OH frequency shifts, OH bonded distances, hydrogen bond energies and ko — — — o force constants, all as a function of the O – – – O distance R. The calculated quantities agree well with those obtained from neutron diffraction, infrared, and other experimental studies. Because of the assumptions involved, this model is best used to describe the properties of hydrogen bonds in crystals. The model is also capable of extention to describe the properties of other types of hydrogen bonds such as HFH, NHN, NHO, OHN, etc.

Infrared Study of the Effect of Solvent upon ν(NH) in Pyrrole

New data are presented on the NH group stretching frequency of pyrrole in dilute and concentrated solutions in fourteen different solvents and in several solvent mixtures. It is shown that in nonpolar solvents ν(NH) of pyrrole obeys the Kirkwood-Bauer relationship, δν/ν=C(D—1)/(2D+1), where C is a constant, and D is the solvent dielectric constant. Furthermore, it is shown that C is only slightly affected as ν(HCl) of hydrochloric acid, ν(OD) of methanol-d, or ν(OH) of methanol, ethanol, propanol, or phenol is substituted for the ν(NH) of pyrrole. The deviations from the Kirkwood-Bauer relationship produced by polar solvents and aromatic hydrocarbon solvents are analyzed in terms of hydrogen bonding and the formation of molecular complexes. The effect of solvent upon band intensity is also briefly examined. A classification of types of OH and NH solution frequencies is suggested.

The Infrared Spectra and Structure of LiOH, LiOH·H2O and the Deuterium Species. Remark on Fundamental Frequency of OH-

The infrared spectrum of a thin path of solid LiOH and LiOH·H2O (undeuterated, partially deuterated, and completely deuterated) has been observed. The spectra indicate that both hydrogens from each water molecule are used to form strong hydrogen bonds in the hydrate. The results serve to substantiate the crystal structures previously determined by x-ray diffraction. For LiOH the absorption maximum occurs at 3678±1 cm-1; the fundamental frequency of OH- in LiOH is 3839±10 cm-1. The spectrum of LiOH·HDO exhibits an anomaly in the bending frequency of HDO.

The Frequency of the Third Harmonic O—H Band of Methanol in Various Solvents, and the Hydrogen Bonding of Methanol with Aromatic Hydrocarbons

The absorption spectra of dilute solutions of methanol in several solvents have been observed in the region of the third harmonic of the OH band. In non-polar solvents the OH frequency is shifted from its position in the vapor by an amount proportional to (D - 1)/(2D + 1) where D is the static dielectric constant of the medium. In certain polar chlorinated solvents the frequency shift is less, but in aromatic solvents the large shift is taken as an indication of hydrogen bond formation.