G. Jalsovszky

Comparison of ab initio, CNDO/2 and experimental dipole moment derivatives for C2 hydrocarbons and formaldehyde

Abstract Dipole moment derivatives determined by ab initio and CNDO/2 calculations are compared with the corresponding data obtained from infrared intensities. For ethane, ethylene and formaldehyde, the recent results of quadratic force field calculations have been used to calculate experimental derivatives; for the latter two molecules, the individual intensities of certain overlapping bands were determined from the results of rovibrational analysis. The experimental dipole moment derivative with respect to the rocking symmetry coordinate, S 10 , of ethylene has been found to be 0.03 D, as opposed to the value of ca. 0.4 D reported previously. CNDO results agree both in sign and magnitude with ab initio dipole moment derivatives.

Solvent dependence of intramolecular hydrogen-bonds in ethylene glycol derivatives: an FT-IR study

Abstract A number of mono-methyl ethers of (poly) ethylene glycols have been investigated by FT-IR in the gas phase as well as in dilute solutions of CCl 4 , CS 2 , CHCl 3 and CH 3 I. It appears that both nucleophilic and electrophilic solvent interaction causes a decrease in the stretching frequency of an OH-donor. The behaviour of an OH-donor in a 5-RH-bond is similar to that of a monohydroxy-OH as both types of hydroxyl groups have an “open” character towards the solvent. As the OH-proton is strongly shielded in the 8-R and 11-R conformations, the frequencies in CCl 4 , CS 2 and CH 3 I are mainly determined by the positions of the acceptors and the bulk effect of the solvents. In solution, conformations are preferred in which the OH-proton exhibits a large accessibility to the solvent.

Pattern recognition applied to vapour-phase infrared spectra: characteristics of νOH bands

Abstract With the commercial availability of infrared spectrum libraries in computer accessible form, a new application of these libraries, the investigation of structure-spectrum correlations, has become possible in addition to the conventional application, the identification of unknown substances on the basis of spectral search in the library. This paper deals with the νOH bands of alcohols, also including diols and diol monoether type compounds, investigating correlations between chemical structure and the features of spectra. For monoalcohols, the frequencies measured in dilute solution and vapour phase, respectively, are correlated; the former were taken from literature, the latter from the vapour phase spectrum library of EPA. For the other types of compound, vapour phase νOH frequencies of free and hydrogen bonded hydroxy groups were studied, and the differences correlated with the hydrogen bonded structures. Peak maxima were determined by a peak picking program; in the case of overlapping bands Fourier self-deconvolution was applied prior to peak picking. For more seriously overlapping bands least-squares curve fitting was applied. In studying correlations, a cluster analysis method (KMEANS) was also used.

Identification of amide bands in the FTIR spectra of protected amino acids and dipeptides. II. Solution spectra

Abstract Protected amino acids and dipeptides of the type Boc-X-NHCH 3 and Boc-X-Y-NHCH 3 (where XPro, Val, YThr and Boc=t-butyloxycarbonyl) have been investigated by infrared spectroscopy in solution phase. The NH sretching and CO stretching regions of the spectra were studied by means of Fourier self-deconvolution and curve fitting to determine the number, frequency and intensity of band components. The results were interpreted by taking into account the effects of all possible intramolecular hydrogen bonds, including a perturbation effect of a CO…HN bond on the CO group adjacent to the NH.

Some applications of computer enhanced Raman spectroscopy

Abstract Intensity and wavenumber signals were transferred from a Cary 82 laser-Raman spectrometer to a Nicolet 1180 computer, enabling Raman spectra to be acquired in digital form. This has made it possible to store and process Raman spectra by means of computer. The paper discusses the hardware and software aspects of data collection, and briefly mentions some applications.

Infrared and Raman studies of cyclohexane, chlorocyclohexane and bromocyclohexane

Abstract On the basis of the ir vapour spectrum of cyclohexane, the assignment of a weak band at 947 cm−1 to the v15 fundamental is probable. We discovered the completely forbidden v11 fundamental /a2g/ of cyclohexane in the vapour spectrum at 1110.7 cm−1, which has been observed so far in liquid phase only. On the basis of the liquid and solid phase ir and the liquid phase Raman spectra of bromocyclohexane, the vibrational frequencies are given between 1500 and 100 cm−1, along with their distribution among the equatorial and axial conformers between 1500 and 400 cm−1. In addition to C-Br and C-Cl stretching and bending of halocyclohexanes, the breathing modes of the cyclohexane skeleton are also assigned.

Metabolism of flumecinol in humans

1. The metabolism of 14C-flumecinol (3-trifluoromethyl-alpha-ethyl-benzhydrol) was studied in volunteers after a single oral dose of 100 mg (11.1 MBq; 300 microCi). Radioactivity excreted in urine was 78.8 +/- 6.0% of dose and in faeces was 12.0 +/- 5.3% dose in 120 h. 2. Unchanged flumecinol was not excreted in urine, but was present in faeces unconjugated (1.2% dose) and as conjugates of glucuronic and sulphuric acids (10.8% dose). 3. Enzymic hydrolysis showed that all urinary metabolites were conjugated with glucuronic and/or sulphuric acids (77.8% dose). Unconjugated urinary metabolites were not found. 4. The major route of flumecinol metabolism was hydroxylation of the alkyl side chain and/or the phenyl group followed by conjugation. 5. Both the CF3-group and the skeleton of the original compound remained intact during metabolism.

Conformational Effect on CNDO Force Field of Furan-2-Aldehyde

Abstract The complete sets of force constants for both O, O-cis and O,O-trans furand-2-aldehyde conformers were calculated using the CNDO force method. The force constants were corrected by ten empirical scaling factors. The calculated and observed frequencies agree well in most cases. Comparing the force constants of the two conformers, the largest deviations can be found in the interaction terms belonging to the aldehyde group.

Infrared intensities of pregn-4-ene-3,2o-dione derivatives

Abstract The IR absorption intensities of C=O stretching bands of pregn-4-ene-3,2O-dione derivatives have been determined. The individual intensities of overlapping bands were calculated by fitting Gauss-Cauchy sum or product functions to the measured spectrum, and numerically integrating the band components obtained. The C=O stretching intensity of the 2O-oxo group was found to change considerably upon acylation in position 17 or 21, and characteristically different intensities were obtained for the C=O stretching bands of primary, secondary and tertiary acetoxy groups. The results can be utilized in structure elucidation.

GC-IR study of trimethylsilyl ethers

Abstract The gas phase infrared spectra of the trimethylsilyl ethers of 1-decanol, 2-heptanol, cyclohexanol, α-phenylethanol, 3-trifluoromethyl-benzhydrol and 3-trifluoromethyl-α-ethyl benzhydrol (I) were studied by means of GC-IR technique in order to determine characteristic absorption frequencies of the COSi(CH 3 ) 3 moiety. Some metabolites of I, containing further hydroxy groups, as well as their partly or complete trimethylsilylated derivatives, were also studied. Various intramolecular hydrogen bonds were found to exist in the gas phase.