Showing papers in "Journal of Physical Organic Chemistry in 1994"

TL;DR: In this paper, the effects of various imperfections such as slow initiation, termination, transfer and slow exchange on kinetics, molecular weights and polydispersities in chain growth polymerizations are simulated.

TL;DR: In this paper, the LFER equation was applied to various C18 stationary phases with methanol-water, acetonitrile-water and tetrahydrofuran-water buffered mobile phases.

TL;DR: The MM3 molecular mechanics program calculates a fair representation of hydrogen bonding interactions, but to improve the MM3 hydrogen bond potential, a directional term has been added to the hydrogen bonding function as discussed by the authors.

TL;DR: In this article, the superbase gas phase scale was further extended up to proton affinities of ca 1080 kJ mol−1 by use of cyclic and acyclic guanidines and vinamidines.

TL;DR: In this paper, the general solvation equation was applied to the partition of solutes between water and isobutanol, pentanol, hexanol, octanol, decanol and oleyl alcohol, showing that the two main factors that influence partitioning are solute hydrogen-bond basicity and solute volume Vx.

TL;DR: In this article, it was suggested that the traditional method of estimating λin by summing bond displacements weighted by force constants produces values which are significantly too low for systems such as phenylenediamines, where pyramidalization changes are important.

TL;DR: In this paper, structural effects on the melting points of substituted alkanes, both branched and unbranched, ranging in length from 1 to 19 carbon atoms, were successfully correlated with a variant of the intermolecular force equation which included a variable capable of accounting for the packing energy contribution of the alkyl group.

TL;DR: In this article, the critical micelle concentration of solutions of cetyltrimethylammonium bromide and of tetradecyltrimethyltrimaine bromides was determined by a kinetic method.

TL;DR: In this article, the solvatochromic hydrogen bond donor acidity parameter (αmix) of aqueous mixtures of methanol, acetonitrile, propan-2-ol and tetrahydrofuran were determined spectrophotometrically.

TL;DR: In this paper, an empirical formula relating directly H... O interatomic distance to H O interaction energy was used to estimate this energy in intramolecular O − H...O hydrogen bonds calculated for systems of known precise geometry.

TL;DR: The evidence for the mechanisms proposed for aromatic nucleophilic substitution reactions by primary and secondary amines in aprotic solvents of low relative permittivity is reviewed in this paper.

TL;DR: In this paper, the relative free ion acidities of a wide range of CH-acids were studied spectrophotometrically and conductimetrically in solvents of low polarity.

TL;DR: In this article, Fourier transform ion cyclotron resonance (FT-ICR) spectrometry was used to study and recheck the proton transfer equilibria for a large number of low-basicity compounds, particularly those which are less basic than H2O.

TL;DR: In this paper, the authors used fundamental chemical structure theory to predict chemical reactivities for a wide range of organic molecules from molecular structure using the chemical reactivity models developed in SPARC (SPARC Performed Automated Reasoning in Chemistry).

TL;DR: In this paper, the transition states for the hetero-Diels-Alder addition of formaldehyde, formaldimine, diazene and nitrosyl hydride to cyclopentadiene were located with ab initio molecular orbital calculations.

TL;DR: In this article, a rigorous procedure was developed for measuring the relative rates of addition of bromine atoms to eleven substituted α-methylstyrenes (1-Y, with Y = CF 3, NO 2, F, CN, Cl, Br, CO 2 Me, Me, COMe, OMe and SMe).

TL;DR: In this paper, the acidities of a representative range of carbon acids were calculated by various levels of ab initio theory and by the semi-empirical methods AM1 and PM3 in order to ascertain what level is necessary in order of obtaining consistently reliable results.

TL;DR: In this article, the substituent effects of acceptor groups were measured for the gas phase basicities of some substituted benzonitriles, methyl benzoates and acetophenones, and for gas-phase acidities of substituted benzoic acids, always in the meta and para positions.

TL;DR: In this article, the relative thermodynamic stabilities of 2-propenylbenzene and the E and Z forms of 1-proplene were determined over the temperature range 50-170°C by chemical equilibration in DMSO solution with t-BuOK as catalyst.

TL;DR: Substrate and positional selectivity in the nitration reactions of benzene and its derivatives (halobenzenes, toluene and o-xylene) by nitric acid and acyl nitrates supported on zeolites H-Y and H-ZSM-11 were studied in this article.

TL;DR: In this paper, the homolytic bond dissociation enthalpies (BDEs) of dialkyl malonates, five alkyl 2-cyanoacetates and nine malononitriles and the oxidation potentials of their conjugate anions, EOX(A−) were measured in dimethyl sulfoxide solution.

TL;DR: In this article, it was shown that the activation process leading to charge transfer (photochemical) nitration is indistinguishable from that leading to electrophilic (thermal) aromatic nitration.

TL;DR: In this paper, the validity of σ-scales for hydrogen abstraction from substituted toluenes by tert-butyl, tertbutyl-peroxyl and tert-Butyl-Peroxyl radicals was investigated using stepwise linear regression.

TL;DR: In this paper, a semi-empirical configuration interaction (CI) algorithm is presented for predicting the ground-state spin multiplicity of open-shell systems, which is qualitatively clearer, facilitating the classification of high and low-spin topologies for isomeric species.

TL;DR: In this article, the nucleophilic substitution reactions of benzoic anhydrides with anilines were investigated in methanol and it was shown that the reaction proceeds by a frontside SN2 attack on either one of the caronyl carbon with a strong interaction between the nucleophile (X) and the leaving group (Z).

TL;DR: In this paper, the conformational properties of diethyl disulphide, a model compound for the disulpide bridges in peptides and proteins, were studied with ab initio methods.

TL;DR: In this article, the gas phase acidity and basicity of thioacetamide and N,N-dimethylthioformamide were measured by Fourier transform ion cyclotron resonance (FT-ICR) mass sectrometry under conditions which minimized the extent of their decomposition.

TL;DR: The gas-phase basicities of eight pyrazoles substituted only at position 4 (R4 = H, NO2, F, Cl, CO2C2H5, CH3, NH2, 1-adamantyl) were measured by Fourier transform ion cyclotron resonance as mentioned in this paper.

TL;DR: In this paper, the absorption spectra of N-methyl-N-(p-nitrophenyl)dimethylenediamine (Ia), N-butyl-p-n-nitroaniline (III), N-(o-nithmyl)trimethylenedienine (IV) were studied at different temperatures.

TL;DR: The structure of PAN in the host was studied by electron paramagnetic resonance spectroscopy as discussed by the authors, and PAN showed a free-radical EPR signal at 2·0035-2·0037 for the hydrogen or 2.0047-2.0049 for the sodium form of the host, similarly to the ermeraldine salt (PAN-2S) or emeraldine base(PAN−2A) form of PAN.