The open source program JChemPaint for drawing 2D chemical structure, its current features, its envisioned further development and the principles enabling researchers and students at places all over the world to collaboratively develop such a program are described

For three series of mono-, di-, and trisubstituted pyridines, respectively, available incremental methods and calculation programs for estimating the corresponding C-13 NMR chemical shifts were employed and compared with the results obtained. The following methods and programs were used for testing them for their accuracy: simple pyridine increments, a simplified increment calculation on the base of benzene increments (program AROSIM(1,2)), the calculation method of Furst and Pretsch(3-6) (Carbon-13 module for ChemWindows), SPECAL from Specinfo(7) (a database founded calculation program), CSPEC2,(8,9) gNMR,(10) CNMR,(11) and HyperNMR,(1,2) respectively.

The tautomerism of triazolopyrimidines in the gas phase as well as in DMSO has been studied with ab inito and semiempirical methods. The self-consistent reaction field method SCI-PCM (self-consistent isodensity polarized continuum model) has been used to represent solvent effects in the ab inito HF/6–31G∗ calculations. Electron correlation was included at the second-order Møller-Plesset perturbation level (MP2). The calculated equilibria of tautomerism, taking solvent effects into account, are in good agreement with the 15N NMR spectroscopy data.

The 13C NMR spectra of a large variety of 7-OH (7-SH, 7-NH2) substituted 1,2,4-triazolo[1,5-a]pyrimidines were studied and assigned by a whole arsenal of 2D NMR methods. The C-7 chemical shifts were not sufficiently characteristic to differentiate the lactim and the three lactam tautomers of the compounds studied. However, the 15N NMR resonances, which were assigned by the various possible N,H coupling constants, proved that the 7-OH- and 7-SH-substituted 1,2,4-triazolo[1,5-a]pyrimidines exist as an equilibrium of the N4H and the N3H tautomers, which is fast on the NMR time scale. PM3 quantum-chemical calculations corroborate this result obtained experimentally.

The Assignment of the 13C-NMR Chemical Shifts of Substituted Naphthalenes from Charge Density with an Artificial Neural Network Neuronal networks are a new possibility to work with blurred data and informations. In this article, the use of a multilayer network with backpropagation of errors for the prediction of the 13C-chemical shifts of a series of substituted naphthalenes from the σ- and π- charge density of the corresponding carbon atoms (calculated by means of the PIMM program) will be described. The average uncertainty for the estimation of the 13C-chemical shifts of monosubstituted naphthalenes is only 2.1 ppm, for naphthalenes with more than one substituent about 4 ppm.

A computer program with many useful functions for the prediction and assignment of the C-13 NMR spectra Of substituted benzenes, naphthalenes, and biphenyls is described. Additionally, for benzenes and naphthalenes, the program proved useful in searching for the types of substituents and their positions on the rings of the studied aromatic compound.

A wide variety of push-pull alkenes were studied by means of variable-temperature H-1 and C-13 NMR spectroscopy with respect to the configuration/conformation and the barriers to rotation about partial C-C and C-N double bonds. For the assignment of the C-13 NMR spectra especially the semi-selective INEPT pulse sequence and an incremental system for estimating the C-13 chemical shift values of aromatic carbon atoms proved useful. The nfluence of thioether, sulphone and sulphoxide moieties in the acceptor part of the push-pull system on the pi-electron distribution is critically considered.