Jimmie W. Brasch

Hydrogen bonding in solid alcohols

Abstract Polarized ir spectra of single crystals of solid alcohols have shown that the OH stretching vibration, v (OH), is always split into two components. Spectra of partially-deuterated solid alcohols have demonstrated that the appearance of two bands is due to crystal splitting. This splitting can be explained by nearest-neighbor or first-order coupling of the vibrations of adjacent OH groups along the hydrogen bond chain. The decoupled OH stretching vibration of these alcohols gives a narrow singlet absorption with a half bandwidth as low as 30 cm −1 . Thus, v (OH) of solid alcohols is not inherently broad, but gains breadth as a result (direct or indirect) of the coupling between OH groups. A study of partially-deuterated liquid alcohols indicates that coupling plays only a small part in the v (OH) bandwidth in liquids. Therefore, different mechanisms control the OH bandwidth in liquid and solid alcohols.

Polarized infrared spectra of single crystals of ethyl alcohol

Abstract Polarized mid-infrared spectra of single crystals of ethyl alcohol and its deuterated derivatives have been obtained using a diamond-window high-pressure cell for both the crystal growing and the spectral measurements. Lattice frequencies have been determined from the infrared spectra of polycrystalline samples at low temperatures. From the dichroic measurements, a crystal structure, C 2 h 6 - A 2/a, is proposed. All of the polarized infrared bands are interpreted on the basis of this structure, including the splitting of the OH stretching vibration into a broad and a sharp component. This latter phenomenon has been interpreted in terms of coupling and a tendency towards a tautomerism for some of the OH stretching vibrations of an infinite zigzag hydrogen-bonded chain.

Micro-Diffuse Reflectance and Matrix Isolation Fourier Transform Infrared Techniques for the Identification of Tetrachlorodibenzodioxins

Micro-diffuse reflectance Fourier transform infrared (DRIFT) and matrix isolation (MI) Fourier transform infrared spectra of the 22 tetrachlorodibenzodioxin (TCDD) isomers have been recorded. The DRIFT and MI techniques required about four minutes and one-half minute, respectively, of signal averaging to produce high signal-to-noise (S/N) spectra on low-nanogram-level samples. Spectral subtraction was employed to remove DRIFT solvent impurity interferences. The validity of the DRIFT subtraction technique was demonstrated by comparison of the corrected DRIFT, with the chromatographically pure, MI spectra. The reproducibility of DRIFT frequencies and intensities was tested by comparison of the 1,3,7,8-TCDD spectra from samples independently prepared by two analysts. The MI technique successfully identified 2,3,7,8 in environmental samples. MI spectral subtraction was applied to one sample to remove a coeluting impurity. The DRIFT and MI spectral techniques, used in conjunction with modern chromatographic separation and spectral subtraction, are very promising for the on-line or off-line differentiation of low-level toxic isomeric compounds.

Polarized ir spectra of single crystals of propanoic acid

Abstract Single Crystals of propanoic acid were grown in a diamond-window Cell under high pressure at room temperature. Polarized ir Spectra of the Single Crystals were investigated and assignments of the Bands were Made taking the Crystal Structure into Consideration. Mid- and far-IR Spectra of the acid and Some deuterated acids in various physical States were also investigated and all of the observed Bands were interpreted in terms of a hydrogen-bonded Cyclic dimer. The only exception was the vapor at about 100° which Showed a Spectrum for Monomeric acid without hydrogen Bonds. A rough Normal-coordinate Calculation was Carried out for the out-of-plane vibrations of the dimers.

Past Results and Future Prospects of the Far-Infrared Studies of Hydrogen Bonding

In the past five years the number of papers concerned with far-ir studies of hydrogen bonding has increased by an order of magnitude. The results of some of these papers are presented in this review. Most of this work is concerned with the assignment of low frequency hydrogen bond vibrations. Since the major problem is reliable assignments, we discuss techniques used in making the assignments and emphasize the past work in which attempts have been made to substantiate those assignments. These assignments are discussed in terms of the different hydrogen bond vibrations associated with various types of hydrogen bonds. The main needs for future far ir hydrogen bond studies are listed.

Far infrared studies of hydrogen bonding in carboxylic acids—II: The n-alkyl acids, propanoic to undecanoic

Abstract Far infrared spectra of the series of n-alkyl acids from propanoic to undecanoic were obtained in both the liquid and solid states. The hydrogen bond stretching vibration of the liquid acids has been observed and assigned. From the solid state spectra it was possible not only to assign the hydrogen bond stretching, and hydrogen bond twisting vibrations, but also to differentiate these vibrations from the C-C torsion frequencies. By use of both mid and far infrared data, these acids were shown to be hydrogen bonded cyclic dimers in both liquid and solid states.

Micro-Diffuse Reflectance And Matrix Isolation Fourier Transform Infrared Techniques For The Identification Of Tetrachlorodibenzodioxins

Diffuse reflectance infrared Fourier transform (DRIFT) and matrix isolation gas chromatography Fourier transform infrared (MI/GC/FT-IR) spectra of the 22 tetrachloro dibenzodioxin (TCDD) isomers have been measured. The spectrum of each TCDD isomer is unique.