Tautomerism and the spectroscopic properties of some 4,6-disubstituted pyrimedines

Tautomerism of some 4,6-disubstituted pyrimidines (with the electron-donor groups such as OH, SH and NH₂) is discussed with regard to their electronic absorption spectra. The spectra of different tautomeric forms of the molecules are satisfactorily interpreted by means of the Pariser—Parr—Pople type of calculations.     

Anordnung und Orientierung kationischer Tenside auf ebenen Silicatoberflächen

Zusammenfassung Die n-Alkylammoniumderivate der glimmerartigen Schichtsilicate können als Modellsubstanzen für die Anordnung kationischer Tenside an Festkörpergrenzflächen herangezogen werden. Im ersten Teil der Arbeit wird die Darstellung durch Kationenaustausch aus den natürlichen Schichtsilicaten beschrieben. Es wird ausführlich auf die Fehlerquellen hingewiesen, die reproduzierbare Messungen erschweren.

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Summary The n-alkylammonium derivatives of mica-type layer silicates are suitable models for studies about the arrangement of cationic tensides at solid interfaces. Part I of the paper deals with the preparation of these compounds by a simple cation exchange reaction. Sources for errors in obtaining reproducible data are discussed in detail.

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Mit 1 Abbildung in 3 Einzeldarstellungen und 3 Tabellen     

The Interaction of Walsh-Orbitols in Diademane and Related Hydrocarbons

To obtain further information concerning the interaction between Walsh-orbitols of ‘conjugated’ cyclopropane rings, the photoelectron spectra of the following compounds have been recorded: bicyclo[4.1.0]heptane 1 , cis- and trans-tricyclo[5.1.0^{3, 5}]octane 2, 3 , diademane 4 , trans-pentacyclo[3.3.2.0^{2, 9}.0^{4, 10}, 0^{6, 8}]decan 5 and bicyclo[4.1.0]heptene-2 6 . The first bands in the PE.-spectra of these compounds have been assigned on the basis of a ZDO HMO-approximation. For 2 and 4 the value for resonance integral between linked 2p atomic orbitals of two adjacent eclipsed cyclopropane rings is found to be ?1.73 eV.     

The infinite time limit for the time-dependent Born-Oppenheimer approximation

We analyze the Schrödinger equation , whereH() is the hamiltonian of the molecular system consisting of nuclei with masses proportional to ^–4 and electrons with masses of order 1. Using the Born-Oppenheimer method we construct the leading order asymptotic expansion to the exact solutions of the equation. We show that if the particles interact through smooth potentials decaying suitably as the distance between particles tends to , then the expansion holds uniformly for all timest[0,). By similar analysis one can show validity of the expansion fort(–,0], thus our results hold for scattering theory.The material in this paper is contained in a dissertation submitted to the faculty of VPI & SU in partial fulfillment of the requirements for the Ph.D. degree.     

Carboxamides of Dihydropyridin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones

Summary. 3-Carboxamides and 3-carboxanilides of 6-alkyl and 6-aryldihydropyridin-2(1H)-ones have been prepared via different reaction pathways. All synthesized amides show hydrogen bonds in their NMR spectra. The 4-hydroxy compounds were obtained as a mixture of tautomers. Their configurations were elucidated by NMR experiments.Received December 16, 2002; accepted December 20, 2002 Published online June 2, 2003     

High-performance flow atomic spectrometry: New nebulization techniques,on-line speciation and on-line sample pretreatment

An interface-free combination of HPLC separation techniques and methods for element determination by atomic spectrometry can be achieved by hydraulic high-pressure nebulization (HHPN). With high-temperature HHPN (300 ( degrees )C) super heated liquids can be nebulized providing aerosol yields of up to 90% in flame AAS. This new nebulization method combines the advantages of HHPN and thermospray techniques (very small aerosol droplets, high aerosol yield, nebulization of saturated salt solutions).     

Photoelectron spectroscopy of isolated multiply negatively charged oligonucleotides

Ultraviolet photoelectron spectroscopy in an ion beam was used to investigate the electronic properties of isolated DNA oligonucleotides [dA(5)-4H](4-) and [dT(5)-4H](4-), carrying four excess negative charges. We find the fourth adiabatic electron affinity to be slightly negative for [dA(5)-4H](4-), while it is positive for [dT(5)-4H](4-). This implies a significant influence of the base composition on energetics, which is in turn relevant for analytic applications and also for charge transport properties.