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Liquids for electronic cigarettes and the vapor generated from them were examined by chemical and biological methods in order to reveal potential risk factors and their acceptability for consumers. Although the majority of the liquids on the market appear to be safe, some aroma compositions have been identified as possibly toxic for human vein epithelial cells, similar to tobacco smoke, thus indicating potential health risks and suggesting suitable test procedures before marketing the liquids.

Numerous hypotheses about how life on earth could have started can be found in the literature. In this article, we give an overview about the most widespread ones and try to point out which of them might have occurred on the primordial earth with highest probability from a chemical point of view. The idea that a very early stage of life was the "RNA world" encounters crucial problems concerning the formation of its building blocks and their stability in a prebiotic environment. Instead, it seems much more likely that a "peptide world" originated first and that RNA and DNA took up their part at a much later stage. It is shown that amino acids and peptides can be easily formed in a realistic primordial scenario and that these biomolecules can start chemical evolution without the help of RNA. The origin of biohomochirality seems strongly related to the most probable formation of the first peptides via the salt-induced peptide formation (SIPF) reaction.

The progress of computational chemistry in the treatment of liquid systems is outlined, and the combination of the statistical methods (Monte Carlo, MC, and molecular dynamics, MD) with quantum mechanics as the main foundation of this progress is emphasized. The difficulties of experimental studies of liquid systems without having obtained sophisticated theoretical models describing the structural entities and the dynamical behavior of these liquids demonstrate that chemistry research is in a transition phase, where theory and high-performance computing have not only become a valuable supplement, but an essential and almost indispensable component to secure a correct interpretation of measured data.

The comparison of two different combined quantum mechanical (QM)/molecular mechanical (MM) simulations treating the quantum mechanical region at Hartree-Fock (HF) and B3-LYP density functional theory (DFT) level allowed us to determine structural and dynamical properties of the hydrated calcium ion. The structure is discussed in terms of radial distribution functions, coordination number distributions, and various angular distributions and the dynamical properties, as librations and vibrations, reorientational times and mean residence times were evaluated by means of velocity autocorrelation functions. The QM/MM molecular dynamics (MD) simulation results prove an eightfold-coordinated complex to be the dominant species, yielding average coordination numbers of 7.9 in the HF and 8.0 in the DFT case. Structural and dynamical results show higher rigidity of the hydrate complex using DFT. The high instability of calcium ion's hydration shell allows the observation of water-exchange processes between first and second hydration shell and shows that the mean lifetimes of water molecules in this first shell (

Monte Carlo simulations have been carried our for 5, 25, 50, and 75 weight% aqueous solutions of hydroxylamine. Changes in the microstructure of the solutions have been evaluated by means of radial and angular distribution functions, coordination number distributions and pair energy anal­ysis. The structure of liquid hydroxylamine is strongly altered by even small amounts of water, whereas water clusters similar to the pure water are maintained up to higher NH2OH concentra­tions. The structural entities in the mixtures are determined by hydrogen bonding and electrostatic arrangement of ligands.

An analytical pair potential function for the Cl--NH2OH interaction energy surface has been constructed based on basis set superposition error corrected ECP/DZP ab initio calculations. The potential has been tested by Monte Carlo simulation of a solution of one chloride ion in liquid hydroxylamine at 32 °C, leading to the conclusion that under these conditions Cl-forms a solvation shell of eight solvent molecules, coordinated via OH hydrogens.

Monte Carlo simulations of a system of 200 water and 24 NaCl molecules at 6 different densities in the range from 0.003 g/cm3 to 0.999 g,/cm3 and T = 125 °C and 225 CC were performed to obtain some insight into cluster formation which should precede and determine the formation of aerosol structures and has possibly played some role in prebiotic atmosphere chemistry. Solute hydration occurs already at very low concentrations mainly in the form of hydrated molecules ("contact ion pairs"). At higher densities larger cluster structures are observed, leading rather continuously to the structure of the supersaturated 7.1 M NaCl solution at the same temperature. Radial distribution functions, coordination numbers and particle interaction energies are discussed with respect to the simulation parameters density and temperature

Monte Carlo simulations for a Cu2+ ion in infinitely dilute aqueous solution were performed on the basis of a simple pair potential function leading to a first-shell coordination number of 8, in contrast to experimental data. A simple method was introduced therefore, which allows the direct construction of a pair potential containing the most relevant 3-body interactions by means of a correction for the nearest neighbour ligands in the ion's first hydration shell. This procedure leads to much improved results, without significant increase in computational effort during potential construction and simulation

A Monte Carlo simulation has been performed for a magnesium ion in 18.45 mol% aqueous ammonia solution at 20 °C, using additive pairwise potential functions obtained from ab-initio calculations. The structural arrangement of the solvent molecules in the vicinity of the ion is discussed in terms of radial distribution functions and average molecular orientations. It was found that the first solvation shell of the ion consists of four water and three ammonia molecules, and the second shell of nine water and five ammonia molecules.

The derivation of an intermolecular potential function for the interaction of two hydroxylamine molecules, based on ab initio SCF-ECP calculations is reported. Ab initio values were compared for selected geometries with those obtained from calculations with much larger basis sets, inluding electron correlation effects by the CEPA method. A total 658 energy values were then fitted to an analytic sum of atom-atom isotropic pair potential functions, whose functional form was given a simple electrostatic interpretation. The major difficulties, arising from the relatively low values of the stabilisation energies of the system and the numerous possibilities to form hydrogen bonds, were overcome by a careful selection of sufficient points on the potential hypersurface, introduction of cut-offs and weight factors. The obtained function was seen to be able to give a good reproduction of the interaction energies and proved suitable in a preliminary MC simulation

The rapid development of computer speed and capacities has given access to computational research methods in wide areas of solution chemistry. The main methods for such applications are quantum chemical calculations on supermolecular systems and statistical simulations of the Monte Carlo and Molecular Dynamics type. The usage of these research tools is illustrated by an investigation on the structure of one molar zinc chloride and copper chloride solutions. Starting from ab-initio calculations, the construction of suitable intermolecular potential functions with approximate 3-body correction terms is shown, and these functions are then used in Monte Carlo simulations for aqueous solutions of the metal chlorides. The results of these simulations are discussed with respect to experimental data, proving that the computational methods can give very detailed information on structural questions, partly exceeding the limitations of experimental approaches

An intermolecular pair potential function for Cu2+-NH3 has been derived based on ab-initio calculations with a ECP-DZV basis set. For copper the original ECP-DZV basis set was modified in order to avoid unwanted charge-transfer effects. The final potential function including anisotropic terms was constructed from a total of 679 configurations.

An analytical pair potential function for the system Cu(II)-water has been derived by means of ab initio calculation of the corresponding energy surface, using double zeta + polarization basis sets and effective core potentials. Tests on the function show that it should be reliable for use in Monte Carlo or molecular dynamics simulations.

Ab initio MO calculations on solvated NaCl adducts are presented. They provide insight into effects to be expected upon oligomerisation of NaCl in aqueous solution or, vice versa, during the last step of the dissolution/solvation process in water. Extrapolation of the data obtained predict the minimal nucleation size for the formation of NaCl crystals to be represented by a (NaCl)~100 aggregate.

An interaction pair potential function for 1,4,7,10-tetraaza-cyclododecane (cyclen) and water has been derived from ab-initio molecular orbital computations. The 250 computed points of the energy surface for the water-cyclen interaction have been fitted with an analytical potential of the form where A, B. C, and D are constants, and qi, and qj are the atomic charges of the i-th atom of water and the j-th atom of cyclen at infinite separation.

An intermolecular potential function for the magnesium complex of 1,4,7,10-tetraazacyclododecane (cyclen) and water has been derived from ab initio molecular orbital calculations. The form of this interaction function is obtained by fitting 250 points of the calculated energy surface.

The intermolecular interaction for ammonia-lithium ion has been investigated based on the LCAO-MO-SCF method, with double zeta basis set including polarization. The potential functions were constructed firstly from 50 ammonia configuration. Then 50 additional random configurations were added to test the quality of the function. The results show that even 100 configurations are not enough to obtain convergency, but the quality of the function obtained by well-selected points of the surface is already sufficient for simulation purposes.

The influence of small monovalent metal ions on hydrogen bonds of aquo-protein complexes is studied on Li+/HCONH2-OH2 as an example. Using results obtained from ab initio calculations with minimal GLO basis sets, the remarkable changes in the hydrogen bond energy and charge distribution, due to metal ion complex formation, are discussed. The metal ion seems to enhance strongly the donor-acceptor interaction of the O ... H-N-C=0 hydrogen-bonded system.

A Monte Carlo simulation has been performed to study the hydration of the magnesium complex of 1,4,7,10-tetraazacyclododecane (cyclen). An intermolecular potential function for magnesium cyclen complex and water, derived from ab initio calculations was used. The first hydration shell results to consist of 18 water molecules.

The effect of N-substitution on the hydrogen bonds of metal ion/water/amide complexes is studied on Li+/N-methylformamide-water as an example. Using the energies and Mulliken atomic populations derived from ab initio calculations with minimal GLO basis set, the Li+/Nmethyl formamide-water and Li+/formamide-water complexes are compared. The transference of the effect of metal ions along the molecular structure seems to have a profound relationship to the bond polarizabilities of the backbone atoms. This can be discussed qualitatively in terms of changes in the Mulliken atomic publications.

The nonlinearity of the NCO group, as to be calculated after the CNDO method and in agreement with some experimental data, has been investigated systematically. The energy values, calculated for different angles, show the nuclear repulsion energy to be the determining factor for the bent (trans-) configuration of these compounds. The extent of this angle cannot be explained with classical chemical characteristics. A significant correlation is found, however, with the electronic situation at the C-atom, whose net charge and covalent bonding are likewise influenced by the NCO angle.

The quality of wavefunctions for complex systems derived by either “full” ab initio MO-SCF calculations or within the MESQUAC-MO framework [1] is investigated comparing chemically interesting quantities as atomic and overlap populations and the character of the chemical bond. A direct relation between the results of both methods is shown to exist, allowing an extrapolation of the much less time consuming MESQUAC computations to the “full” MO SCF level. Hydrate complexes of main group and transition metal ions have been chosen for some practical applications

The preparation of two new alkaline earth metal complexes with acetylacetone, where the latter acts as a ligand in its diketoform, is described. The solid compounds are characterized by elemental analysis, IR spectra and X-ray diffraction patterns.

The bonding in the F5SO--ion is discussed by comparing the results of CNDO MO calculations on this and some related compounds with data obtained from IR- and RAMAN-spectra. Theoretical and experimental results are found to be in good agreement. The-yet not prepared -acid F5SOH is discussed with respect to its stabilization and acidity.