Bratislav Ž. Jovanović

Effect of substituents on the 13C chemical shifts of the azomethine carbon atom of N-(phenyl substituted)pyridine-3- and -2-aldimines

Abstract 13 C chemical shifts of the azomethine carbon atom for N-(substituted phenyl)pyridine-4-aldimines, 4-Py–CH N–C 6 H 4 –X, X having a wide range of substituent effects, have been determined in CDCl 3 solution. Exceptionally good Hammett correlations of 13 C NMR chemical shifts of azomethine carbons with electrophilic substituent constants σ + points out to a strong resonance interaction of substituents on the aniline ring with the azomethine carbon atom of the investigated imines. The increased demand for electrons in the investigated system is being compared with that of the N-benzylidenaniline. The mode of transmission of substituent effects, both inductive and resonance, in both systems, is discussed.

13C NMR spectra of pyridine chalcone analogs

Abstract 13 C NMR spectra of two series of pyridine chalcone analogs were determined in deuterated dimethylsulphoxide (DMSO-d 6 ). It was established that these compounds were in more stable E -configurations except for the 4-pyridalacetophenone which was in Z -configuration. On the basis of the Hammett correlations of 13 C NMR chemical shifts of the ethylenic bond carbon atoms and the σ values for the pyridine “aza” groups, the polarization of ethylenic bonds were discussed. It was established that the opposite effect of the pyridine substituents at the electronic density distribution in pyridalacetophenone and cinnamoylpyridines depends on its direct bonding to the ethylenic carbon or the transmission electronic effects via the carbonyl group, respectively.

Effect of Substituteents on the 1H and 13C NMR Chemical Shift of trans-Pyridineacrylic and Substituted trans-Cinnamic Acids

The principles of linear free energy relationships were applied to the 1 H nmr and 13 C nmr chemical shifts induced by substituents in three isomeric trans-pyridineacrylic and substituted trans-cinnamic acids. The data for the carboxy proton chemical shift correlated well with the simple Hammett equation. Tafts dual substituent parameter equation was used for the interpretation of the balance of the inductive and resonance effects through the ethylenic bond for the C α and C β 13 C nmr shift. Using the nuclear Overhauser method, the conformation of the carboxylic group in 2-pyridineacrylic acid was determined, and its unexpected behaviour in both 1 H nmr chemical shifts;and in the previously studied reaction with diazodiphenylmethane was interpreted by the increased electron density in the π-electronic system favoured by the orbital symmetry of the part of the acid molecule

Kinetics and mechanism of the reaction of substituted 4-pyrimidine carboxylic acids with diazodiphenylmethane in dimethylformamide

Correlation of the data for the reaction of 11 substituted 4-pyrimidine carboxylic acids with diazodiphenylmethane (DDM) in dimethylformamide (DMF) with calculated atomic charges on the carboxylic group showed that the reaction in this solvent may proceed via a concerted transition state.

Kinetics of Spontaneous Hydrolysis of O-(2,2-Dimethylcyclopentyl)-methylfluorophosphonate and of Hydrolysis During Constant pH Value of the Reaction Medium

Hydrolysis of O-(2,2-dimethylcyclopentyl)-methylfluorophosphonate in dilute aqueous solution was investigated. Rates of hydrolysis of O-(2,2-dimethylcyclopentyl)-methylfluorophosphonate were measured as a function of pH (in the range from 3 to 9 and without keeping the pH-value constant--in a spontaneous hydrolysis) and temperature (in the range from 25°;C to 40°;C). Objective of these investigations was to simulate real processes of degradation of highly toxic compounds in nature, getting information about rates of degradation, in order to obtain most efficient systems for their removal.

Transmission of electronic effects through the vinyl group. Reactivities of the (E)-α-4-substituted phenyl-β-pyridine acrylic acids

The reactivities of a series of 18 (E)-α-4-substituted phenyl-β-(3N and 4N)pyridineacrylic acids, with a wide range of substituent effects, were investigated in their reaction with diazodiphenylmethane, in dimethylformamide at 30°C, by the known spectrophotometric method. The Hammett equation in its original form has been applied to the results, using the sum of substituent constants from the both aromatic nuclei, but the overall correlation was only fair. Better insight into the transmission of substituent effects was obtained using Tafts Dual Substituent Parameter (DSP) method, where it was possible to distinguish the contributions from the inductive and resonance effects of the substituents

Substituent efects on the carbon-13 chemical shifts in α-phenylpyridylacrylic acids

Abstract The 13 C N.M.R. spectra of some substituted α-phenylpyridylacrylic acids, α-phenyl, α-(3-pyrydyl) and α-(3-pyrydyl-N-oxide) cinnamic acids were determined in deuterated dimethyl sulfoxide (d 6 -DMSO). It has been shown that the subsitutent chemical shifts (SCS) for C β atom ethylenic bond of the examined compounds correlated linearely with the summ of the corresponding substituent constants in the both rings (σ x + σ Y ). This correlation was interpreted as evidence that the electronic effects of both substituents are involved in conjugated aromatic system.

Kinetics of the Reactions of Pyridine and Pyridine- N -oxide Carboxylic Acids and Substituted Benzoic Acids with Diazodiphenylmethane in Various Alcohols

Solvent effects on the reactivity of pyridine and pyridine-N-oxide carboxylic acids and p-substituted benzoic acids in their reaction with diazodiphenylmethane (DDM) in alcohols have been investigated and the rate constants interpreted by Hammett parameters using multiple regression analysis; the influence of solvents on the reactivity of these acids with DDM has not been reported previously.

Effect of substituents on the 13C NMR chemical shifts of para-substituted α-phenyl-β-pyridylacrylic acids

Abstract The 13 C NMR spectra of para-substituted α-phenylcinnamic and 3- and 4-pyridylacrylic acids, with a wide range of substituents effects, were determined in deuterated dimethylsulfoxide (DMSO- d 6 ). The effect of substituents in both the α-phenyl and β-pyridine groups in these acids is investigated using linear free energy relationships and multiple regression analysis as applied to 13 C NMR chemical shifts of the C α and C β of the ethylenic bond and the carboxylic group carbon. Dissection of the α-phenyl substituent effects into the inductive and resonance components, using the dual substituent parameter (DSP) method, points to a blend of inductive and resonance effects in the π-electronic system.

Spectrophotometric method for the parallel determination of 2,2′-dichlorodiethyl sulphide and 2-chloroethyl vinyl sulphide in the reaction of 2,2′-dichlorodiethyl sulphide with sodium 2-methoxyethoxide

Application of the spectrophotometric method based on thymolphthalein for the parallel determination of 2,2′-dichlorodiethyl sulphide and 2-chloroethyl vinyl sulphide in the reaction between sodium 2-methoxyethoxide and 2,2′-dichlorodiethyl sulphide in 2-methoxyethanol, catalysed by diethylenetriamine, is presented. The suggested procedure permits the recording of the kinetics of this reaction although thymolphthalein reacts with both the starting reactant (2,2′-dichlorodiethyl sulphide) and the reaction intermediate (2-chloroethyl vinyl sulphide). Good agreement was found between this method and previously described methods for following this reaction.