L. V. Ermolaeva

A Watersoluble Sulfonatomethylated Calix[4]resorcinarene as Artificial Receptor of Metal Complexes

The binding of different sized and shaped metal complexes [Co(His)2]ClO4(1), [Co(en)2C2O4]Cl (2) and [K18-crown-6]SCN (3)(en-ethylendiamine, His-L-histidynate-anion) with a new tetrasulfonatomethylcalix[4]resorcinarene([H8X]Na4) was investigated in neutral and alkaline aqueous media by NMR and pH-metrictitration methods and compared with those of recently studied NMe4Br (4). The resultsobtained indicate that the outer-sphere coordination of complexes 1–3 by[H8X]4- proceeds via the interaction of hydrophobic fragments of the guestswith both the negatively charged rim and the hydrophobic cavity as a π-base. Thenature of binding does not change for cations 1, 2 and 4 on going from[H8X]4- in neutral to [H4X]8- in alkaline media, while the inclusionof 3 decreases on going from [H8X]4- to [H4X]8-.

SYNTHESIS OF NEW PHOSPHORUSCONTAINING THREE-DIMENSIONAL STRUCTURES ON THE BASIS OF CALIX[4] RESORCINARENES

Abstract Phosphorylation of calix[4]resorcinarenes with long chain aliphatic radicals (R=C6, C,. C,) (1a,b,c) with a number of P(III) derivatives i.e. triamido- and diamidophosphites, triphenylphosphite, monoand polyhalogenides of P(III) is described. A series of phosphoamide cavitands (2), (3) were obtained. A new three-dimensional “container”- like structures, in which tetraresorcinol fragments are connected by means of phosphite bridges (13,14) were formed in the reaction of (Ib) with (-) bis(N,N-diethylamido)menthylphosphite, phosphorus trichloride and triphenylphosphite. Phosphorylation of calix[4]resorcinarene (1c) with chloroanhydrides of chloromethylphosphonic and bis(chloromethyl) phosphinic acids results in completely or partially posphorylated products depending on the reaction conditions. The synthesis of dimeric “head to head” macrocyclic derivative of chlormethylphosphonic acid (19) is described. Structures and properties of synthesized compounds were discussed on the basis of physical and q...

Conformational analysis and regioisomerism of mono- and diadducts of O,O-diisopropyl isoxazolinophosphonate with C60

Theoretically, cycloaddition of two molecules of phosphorylated nitrile oxide to C60 can give rise to 22 regioisomers. A simple convenient nomenclature was proposed for their classification based on the well-known Hirsh nomenclature. A combination of HPLC, semiempirical quantum-chemical PM3 calculations, and the dipole moment method demonstrated that the equatorial, trans-4(tt), and trans-3(tt) adducts are most probable.

GAS PHASE REACTION OF F- WITH CHLOROCYCLOPROPANE. AB INITIO STUDY OF ELIMINATION AND SUBSTITUTION

Abstract The stereochemistry of elimination in chlorocyclopropane was investigated using ab initio (6-31(+)G∗//HF/6-31(+)G∗) calculations. The competitive SN2 route was also considered. Transition states were located for the E2(anti), E2(syn) and SN2 reactions. The three-membered ring has a pronounced effect on the syn/anti preference of E2 elimination; the barrier of syn elimination (22.2 kcal mol−1) is only 3.6 kcal mol−1 larger than that of anti elimination. The small syn/anti difference is related to the inherent periplanarity of the syn transition state and the torsional ring strain of the anti transition state. Comparing the reaction of F− with cyclopropyl, cyclopentyl and cyclohexyl chlorides, it was found that the tendency for anti elimination is especially reduced in the three-membered ring because of the non-periplanar conformation of the anti transition state. According to theory, the initial reactant complex can react further via the E2(anti) pathway or SN2 substitution. The barrier to substitution is 2.5 kcal mol−1 and the SN2 pathway dominates over elimination in this system. At the MP2/6-31(+)G∗//HF/6-31(+)G∗ level, the SN2 pathway has a lower activation barrier by 7.3 kcal mol−1 compared with the E2(anti) pathway.

Theoretical study of bimolecular elimination (E2) reactions. Possibility ofsyn E2 elimination in the series of 2-R-2-R'-1-halocyclopropanes

Reactions of the methoxide ion with substituted halocyclopropanes, which result in E2 elimination, have been studied by the semiempirical quantum-chemical AM1 method. The transition states corresponding totrans andcis routes have been localized. The energetic predominance of thetrans route over thecis route is reduced by 2.6 kcal mol−1 on going from 1-chloropropane to chlorocyclopropane because of the features of cyclopropane geometry. It has been demonstrated that, in the gas phase,cis elimination may predominate overtrans elimination for a particular stereoisomer of 2-cyano-2-methyl-1-halocyclopropanes due to weakening of orbital interactions and Coulomb repulsion between the cyano group and the MeO− anion in thetrans E2 transition state.

Intermolecular interactions of tetraanions of macrocyclic tetraresorcinol in H2O—DMF solutions

According to the data of pH-metric titration, macrocyclic tetraresorcinol (1c) dissociates stepwise with the abstraction of one, two, and four protons. Aggregation of tetraanions of 1c in H2O-DMF solutions was detected by conductometry. The degree of aggregation increases as the size of the counterion decreases and the content of DMF in the solvent mixture increases.

The effect of substituents (CH3 and NH2) in positions 4 and 6 on the acid-base properties of 2(1H)-pyrimidinethiones

The acid-base properties of 4,6-dimethyl- and 4,6-diamino-2(1H)-pyrimidinethiones (1 and2) were investigated by potentiometric titration. Dissosiation of1 and protonation of its anion occur in two steps, the first of which affords the deprotonated dimer [HA2)−. The relative stability of the dimer depends on the nature of the solvent. The effect of kinetic factors on the acid-base behavior of1 was elucidated by comparing the results of potentiometric titrations carried out under various kinetic conditions. It was concluded that the difference between the acid-base properties of1 and2 results from the electron-donating effect of the amino groups.

Acid-base properties and complex-forming ability of 4,6-dimethyl-2-(1H)-pyrimidinone (thione)

Complex formation of 4,6-dimethyl-2-(1H)-pyrimidinone (thione) with dysprosium(III) tris(acetylacetonate), Dy(acac)3, in 80% (v/v) aqueous methanol was investigated by pH-metric titration and paramagnetic birefringence. Due to its higher basicity and lower acidity, 4,6-dimethyl-2-(1H)-pyrimidinone is coordinated by Dy(acac)3 without deprotonation, whereas its thio analog is coordinated in the deprotonated form. Due to the higher acidity of 4,6-dimethyl-2-(1H)-pyrimidinethione, the complex of its anion with Dy(acac)3 is much more stable than that derived from the oxo analog, as inferred from the comparison of the stability constants.

Ab initio study of oxaphosphaalkyne P=C-OH and its isomers

Anab initio study on HP=C=O → P≡C-OH isomerization has been performed at the 3-21G(d(P)), 4–31G(d(P)) and 6–31G** levels. In contrast to analogous transformation of 1-aza-3-phosphaallene, this process is endothermic in the gas phase. It proceedsvia a [1,3]H shift without an intermediate. The route, including two subsequent [1,2]H shifts, leads to phosphinidene.

ELECTRICAL PROPERTIES AND INTRAMOLECULAR ELECTRONIC INTERACTIONS OF BENZOTRIHALIDES

Conclusions1.The esential nonadditivity of the electrical properties — the DMs and EPs — was established in the benzotrihalide series.2.The interaction between the aromatic ring and the CHal3 group in benzotrichloride and the bromide is realized by the π(Ar)-π*(CHal3) mechanism. In the corresponding p-nitro derivatives, the hyperconjugational effect bears the opposite character of p(Hal)-π*(Ar). The inductive effect is dominant in the benzotrifluorides.