M. I. Kabachnik

An NMR study of optical isomers in solution

Abstract NMR 31P-{1H} spectra of stereoisomeric N - [S - (methylethoxyphosphinyl) - thioglycolyl]valines in solution to reveal association of the molecules, and interaction of the chiral centres. Under fast inter-associate exchange in achiral media, these interactions lead to the following: (i) The chemical shift of the racemic mixture of enantiomers deviates from the shift of the individual species; (ii) the spectra of non-racemic mixtures are doublets; (iii) there are 2n lines in the spectrum of a mixture containing unequal concentrations of stereoisomers with n asymmetric centres. The integrated intensity ratio is equal to the concentration ratio in all cases. The concept of statistically controlled associate diastereomerism (SCAD) is introduced and the respective formalism is given to describe the spectral effects accompanying variations of temperature and concentration. It is also shown applicable to more complicated cases involving ion exchange of chiral fragments between stereoisomers.

Coordination and organometallic compounds based on the stable 1-hydroxy-2,4,6,8-tetrakis(t-butyl)phenoxazin-10-yl radical

Abstract A new method for the preparation of a stable 1-hydroxy-2,4,6,8-tetrakis(t-butyl)phenoxazin-10-yl radical by oxidation of 3,5-di-t-butyl-ortho-aminophenol with 3,5-di-t-butyl-ortho-benzoquinone is reported. Interaction of the radical with the coordination or the organic compounds of various metals has been studied.

The electron influence of substituents containing trivalent phosphorus

Abstract The groups containing trivalent phosphorous belong to the second-kind substituents although they possess a lone electron pair. β-Orientation of piperidine addition to vinyl-PIII-compounds, ionization constants of phosphorus-substituted benzoic acids or phenols as well as protophylic hydrogen exchange reaction in tertiary phosphines are all indicative of this fact. We determined the σ-Hammett- and σ-constants and calculated σI- and σR-constants for Ph2P-, Ph2P(O)-, Ph2(S)- and Ph2N-groups. The results show either no or minor ϱ-π-conjugation effect and the presence of acceptor conjugation. The lone electron pair of trivalent phosphorus displays a weaker ϱ-π-conjugation than those of other third period elements. The reason for this may possibly be an increased s-character on a lone pair of phosphorus electrons, which agrees with the values of valence angles in PIII-compounds.

Complexation of [ω-diphenylphosphinoalkyl]diphenylphosphine sulphides with AgNO3

By reaction of [ ω -diphenylphosphinoalkyl]diphenylphosphine sulphides Ph 2 P(CH 2 ) n P(S)Ph 2 ( n = 2–4) (L 1 −L 3 ) with AgNO 3 in CH 3 CN crystalline complexes with the composition metal:ligand 1:1 [Ag(L 1 )NO 3 , Ag(L 2 )NO 3 , Ag(L 3 )NO 3 ] and 1:2 [Ag(L 1 ) 2 NO 3 , Ag(L 3 ) 2 NO 3 ] were isolated. According to the X-ray analysis data, the crystals of Ag(L 1 )NO 3 are constructed from centrosymmetric dimeric molecules based on the 12-membered macrocycle AgSPCH 2 CH 2 PAgSPCH 2 CH 2 P ¯ . Each of the neutral ligands L 1 is a bridge between two silver ions and each of the silver ions is coordinated by a chelating NO 3 group. According to the IR spectra, the other 1:1 complexes also have an analogous structure. In the 1:2 complexes the coordinated NO 3 groups of the 1:1 complexes are replaced by the phosphine sulphide ligand. The downfield shifts of the signals of P III and P V atoms in 31 P NMR spectra of 1:2 complexes in comparison with the free ligands L 1 and L 3 reflect a participation of the P III atom and P=S group in complex formation.

Cholinesterases of aphids—II: Anticholinesterase potency and toxicity of different organophosphorous inhibitors for spring grain aphid Schizaphis gramina rond

Abstract Anticholinesterase potency and toxicity for spring grain aphids of 52 organophosphorous inhibitors (OPI) of different structures were investigated. As regards sensitivity to OPI, the acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) of the spring grain aphid are shown to differ significantly from the “typical” cholinesterases, i.e. from human erythrocyte AChE and horse serum BuChE, which is presumably associated with differences in the structures of the active surface of these enzymes. The extremely high sensitivity of spring grain aphid AChE to cationic OPI containing the onium atom in the leaving part of the molecule indicates the fundamental importance of the anionic site in the active centre of the enzyme. By contrast, spring grain aphid BuChE has low sensitivity to OPI, typical of the cationic type, which suggests that it has no anionic site. Correlation was established between the toxicity and anticholinesterase potency of OPI which contain no cationic groups or bulky hydrophobic radicals.

Tautomerism in silicon-containing free radicals

Abstract Silicon-containing free radicals with 3,6-di-t-butylpyrocatechinic ligands have been investigated by ESR method. Intramolecular migrations of free valence and bond was found for these systems. It was considered in terms of intramolecular radical substitution.

The application of the Hammett equation to the theory of tautomeric equilibrium—II: Tautomerism of α-arylsulphaminopyridines☆

Abstract In general principles the application of the Hammett equation to the study of tautomeric equilibrium has been investigated. It has been shown that the pKa - σ plot for the dissociation constants of tautomeric acids is characterized by the deviations from the linear Hammett dependence, no deviations being observed except under definite conditions. The deviations from the linear dependence are related to the tautomeric equilibrium constant by the relationship KT = 10a − 1 = 1 10 b − 1 with “a” and “b” being the deviations of the curve pKa = f(σ) from the asymptotes. These principles were applied to the investigation of the tautomeric equilibrium of σ-arylsulphaminopyridines, substituted into the benzene ring. Two independent methods—potentiometric and spectrophotometric—were used. The electron releasing substituents have been shown to shift the equilibrium toward the amino forms and the electron attracting ones toward the imino forms. The comparison of the quantitative results obtained by the two methods showed them to be in a good agreement.

Synthesis and physiological activity of new organophosphorus pesticides of 1,3,2-oxazaphosphorinane series

Methods for the synthesis of 2-aryloxy(arylthio)- and 2-alkoxy(alkylthio)-2-thio(oxo)-1,3,2-oxazaphosphorinanes and theirN-substituted derivatives based on the reactions of the corresponding dichlorophosphates, dichlorothio-, and dithiophosphates with 3-aminopropan-1-ol or its substituted derivatives in the presence of Et3N or aqueous alkali under phase transfer catalysis conditions, as well as by the reaction of the tetramethylammonium salt of 2-hydroxy-2-thio-1,3,2-oxazaphosphorinane with alkyl- and acyl halides, by that of 2-chloro-2-thio-1,3,2-oxazaphosphorinane with sodium thiolates, and by other methods, were developed. The compounds obtained exhibit high nematocide activity but low toxicity for mammals. Some active synergists for permethrine were found among these compounds.

Influence of solvent on the strength of cyclic oxygen-containing phosphorus acids

ConclusionsThe dissociation constnats of cyclic oxygen-containing phosphorus acids in absolute alcohol were measured by potentiometric titration in charge transfer circuits.For acyclic phosphorus acids ABPOOH, there is a Brönsted dependence in pK(EtOH)-pk(H2O) coordinates, which does not apply to 1,3-alkylenephosphoric acids, while in the pK(MeNO2)pK(EtOH) coordinates there is a uniform Brönsted dependence for all the acids.

New method for the synthesis of 1-aminoalkylphosphonic acids Communication 1

1. The reaction of aldehydes with dialkyl hydrogen phosphites and ammonia has been investigated and it has been established that when heat is applieda-aminoalkylphosphonic esters are formed; on hydrolysis these yield the free acids. 2. By this methoda-amino phosphonic acids have been synthesized from benzaldehyde, p-tolualdehyde, p-isopropylbenzaldehyde, p-anisaldehyde, piperonal, and vanillin. 3. It has been shown that benzaldehyde reacts with dialkyl hydrogen phosphites and ammonia in the cold with formation ofa-hydroxybenzylphosphonic esters, which, on being heated with ammonia, are converted intoa-aminobenzylphosphonic esters. 4. A mechanism has been proposed for the reaction, in whicha-hydroxyalkylphosphonic esters play the part of intermediate products. A parallel has been drawn between the reaction observed and other reactions: Zelinskys reaction, Rodionovs reaction, and the formation ofa-amino sulfonic acids from aldehydes and ammonium bisulfate.