Experimental and theoretical IR and Raman spectra of picolinic, nicotinic and isonicotinic acids

The experimental and theoretical (B3PW91/6-311++G**) vibrational (IR and Raman) spectra of picolinic, nicotinic and isonicotinic acids (pyridine-2-, -3-, and -4-carboxylic acid, respectively) were studied. Three stable calculated structures were found for picolinic acid: the structure with intramolecular hydrogen COOH?N bond, and the two without hydrogen bond. For the nicotinic acid two stable theoretical structures differ in orientation of the COOH group with respect to the nitrogen atom, whereas for the isonicotinic acid only one form was stable. The theoretical vibrational spectra of the three acids were interpreted by means of potential energy distributions (PEDs) using VEDA 3 program. Next, selected experimental bands were assigned based on the scaled theoretical wavenumbers. Finally, the wavenumbers and intensities for the three isomeric acids were compared and discussed in terms of location of the carboxylic group.     

八乙墓卟啉和四苯基卟啉合钌(Ⅱ)及锇(Ⅱ)的二氧加合物的红外光谱

ＯＥＰ（八乙基卟啉阴离子）和ＴＰＰ（四苯基卟啉阴离子）合钌（Ⅱ）和锇（Ⅱ）的二氧加合物由ｍａｔｒｉｘ分离技术得到（Ｔ＝２０－４３Ｋ，Ｐ＝１０＾－５－１０＾－６ｔｏｒｒ）。为了确定ν（Ｏ２）带的归属应用于同位素取代法＾１６Ｏ２／＾１８Ｏ２。ＩＲ谱说明对于钌的两种加合物（指ＯＥＰ和ＴＰＰ）都有两种异构体，其ν（＾１６Ｏ２）频率为：Ｒｕ（ＯＥＰ）Ｏ２，１１４１和１１０３ｃｍ＾－１；Ｒｕ（ＴＰＰ）Ｏ２，１     

The effect of zeolites on copper uptake by plants growing in contaminated soils

Three-year pot experiments were carried out in a greenhouse with the aim of reducing the copper content in the 2nd link of the soil-plant-animal (man) trophic chain. For this purpose, synthetic zeolites of the 3A, 4A, 5A and 13X type were introduced into copper contaminated soils at levels of 1, 2 and 3% by weight in relation to the soil mass. Mono- and dicotyledonous plants were cultivated in mixtures of soils with the zeolites. The copper content in lettuce grown in the contaminated soil decreased in the presence of zeolites by 29–77%, in grass by 41–78%, in oats by 45–64% and in beets by 21–41%, as compared to the control.     

Application of infrared spectrometry to the study of tautomerism and conformational and configurational isomerism in medical and biochemical agents: N,N'-disubstituted amidines.

Infrared investigations on the v(NH) and v(C = N) vibrations of N,N'-disubstituted formamidines, acetamidines and benzamidines, containing the same or different groups at the amino and imino nitrogen atoms, and of some model compounds (N-monosubstituted amides, imidazoles and 2-aminopyridines), carried out in CCl4 at various temperatures and concentrations, and in other solvents, show that all the amidines studied have the E configuration on the C = N double bond and display conformational isomerism on the C-N single bond. Formamidines exist predominantly in the form of a conformer with a hydrogen atom synperiplanar to the imino nitrogen atom, and can form a cyclic dimer. In acetamidines and benzamidines the other conformer, with a hydrogen antiperiplanar to the imino nitrogen, prevails, and hence they can form mainly linear dimers. Different positions of the v(NH) and v(C = N) bands observed for N,N'-diaryl and N,N'-dialkyl derivatives permit determination of the composition of tautomeric mixtures in N-alkyl-N'-arylamidines.     

Determination of specific heats of some edible oils and fats by differential scanning calorimetry

Measurements of specific heat as a function of temperature were carried out with a differential scanning calorimeter on rape-seed, soybean, sunflower and corn oils and on lard.

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Zusammenfassung Es wurden Messungen der spezifischen Wärme als Funktion der Temperatur von Raps-, Soia-, Sommerblumen- und Mais-ölen und von Schmalz mit Hilfe von einem Dynamische-Differenz-Kalorimeter durchgeführt.

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Computer-aided acquisition and processing of data for caloric measurements with isoperibol calorimeters

The undisturbed temperature equilibration of the vessel in an isoperibol calorimeter must follow an exponential time function. Any caloric effect within this vessel must cause a deviation of this function. A mathematical relation has been derived for linking the extent of this caloric effect and the integral of the temperature-time function.This algorithm has been utilized for a computer program capable for an automatic acquisition of the data of an appropriate digital temperature meter and for the automatic calculation of the calorimetric results.In two different calorimetric units these arrangements have been applied for the following determinations: -specific heat capacities of liquid samples -heats of chemical reactions -reaction rates -heats of vaporization of liquid samples.     

The meaning of the very different OH bandshapes in infrared fundamental and overtone regions of H-bonded methanol

Infrared spectra of methanol in solvents were discussed in the fundamental and overtone region in dependence on the temperature. One absorption band is observed in the fundamental region of the OH stretching vibration, however, the overtone band is splitted into two or more bands. The intensity ratio of the overtone bands changes characteristically with the temperature and with the H-bond strength. This behavior will be explained by different OH transitions, taking into account the OO vibration. A modified Lippincott-Schroeder procedure was used for the calculations of energy values. The splitting of the overtone bands could be assigned to the transitions E(v=0,v′) → E(v=2,v′) and E(v=0,v′) » E(v=2,v′+1), with v′ as OO vibrational quantum-number.