Calorimetric and computational study of 1,3,5-trithiane

To understand the differences in conformational behavior and reactivity of oxygen- and sulfur-containing 1,3,5-heterocyclohexanes, the enthalpies of formation and sublimation of 1,3,5-trithiane, 1, have been measured. The numerical value of the enthalpy of formation for this compound in the solid state is -8.6 +/- 2.6 kJ mol(-1), while the corresponding value in the gaseous state is 84.6 +/- 2.6 kJ mol(-1). The value for the enthalpy of sublimation is 93.2 +/- 0.2 kJ mol(-1). Standard ab initio molecular orbital calculations at the G2(MP2), G2, and G3 levels were performed, and the calculated enthalpies of formation are compared with the experimental data. These experimental and theoretical studies support the relevance of through-space lone pair-lone pair electronic repulsion in the sulfur heterocycle.     

A study of the cationic solid-state polymerization of 1,3,5-trithiane

The effect of various reaction parameters, such as temperature, catalyst, and concentration, on the cationic-initiated polymerization of 1,3,5-trithiane in solid state was studied and the apparent activation energies were estimated. A simple mathematical formula to describe the observed kinetic curves is proposed. The features observed are interpreted in terms of disordering a crystal structure during polymerization.     

Preparation of low-polydispersity poly(methyl methacrylate) in the presence of 1,3,5-trithiane

The mechanism of methyl methacrylate polymerization in the presence of 1,3,5-trithiane was studied.     

Transients in the oxidative and H-atom-induced degradation of 1,3,5-trithiane. Time-resolved studies in aqueous solution

The (*)OH-induced oxidation of 1,3,5-trithiacyclohexane (1) in aqueous solution was studied by means of pulse radiolysis with optical and conductivity detection. This oxidation leads, via a short-lived (*)OH radical adduct (<1 micros), to the radical cation 1(*+) showing a broad absorption with lambda(max) equal to 610 nm. A defined pathway of the decay of 1(*+) is proton elimination. It occurs with k = (2.2 +/- 0.2) x 10(4) s(-1) and yields the cyclic C-centered radical 1(-H)(*). The latter radical decays via ring opening (beta-scission) with an estimated rate constant of about 10(5) s(-1). A distinct, immediate product (formed with the same rate constant) is characterized by a narrow absorption band with lambda(max) = 310 nm and is attributed to the presence of a dithioester function. The formation of the 310 nm absorption can be suppressed in the presence of oxygen, the rationale for this being a reaction of the C-centered cyclic radical 1(-H)(*) with O(2). The disappearance of the 310 nm band (with a rate constant of 900 s(-1)) is associated with the hydrolysis of the dithioester functionality. A further aspect of this study deals with the reaction of H(*) atoms with 1 which yields a strongly absorbing, three-electron-bonded 2sigma/1sigma* radical cation [1(S therefore S)-H](+) (lambda(max) = 400 nm). Its formation is based on an addition of H(*) to one of the sulfur atoms, followed by beta-scission, intramolecular sulfur-sulfur coupling (constituting a ring contraction), and further stabilization of the S therefore S bond thus formed by protonation. [1(S therefore S)-H](+) decays with a first-order rate constant of about 10(4) s(-1). Its formation can be suppressed by the addition of oxygen which scavenges the H(*) atoms prior to their reaction with 1. Complementary time-resolved conductivity experiments have provided information on the quantification of the 1(*+) radical cation yield, the cationic longer-lived follow-up species, extinction coefficients, and kinetics concerning deprotonation processes as well as further reaction steps after hydrolysis of the transient dithioesters. The results are also discussed in the light of previous photochemical studies.     

ESR study of γ-irradiated 1,3,5-trithiane and its derivatives

Radicals formed in γ-irradiated 1,3,5-trithiane and its derivatives at room temperature have been studied by ESR spectroscopy. ESR evidence establishes that 1,3,5-trithiane as well as α- and β-2,4,6-trimethyl-1,3,5-trithiane yield radicals mainly by loss of the hydrogen atom, whereas α- and β-2,4,6-triphenyl-1,3,5-trithiane and 2,4,6-trimethyl-2,4,6-triphenyl-1,3,5-trithiane produce radicals that are parent radical cations, which are also present in small amounts in aliphatic trithianes. Furthermore, in all the spectra examined R–S^.-type radicals are observed. The probable initiation process of radiation-induced 1,3,5-trithiane polymerization is discussed briefly.     

Increase in the content of maleic anhydride units in a copolymer with methyl methacrylate in the presence of 1,3,5-trithiane

The use of 1,3,5-trithiane as agent controlling copolymerization of maleic anhydride with methyl methacrylate allows preparation of the copolymer with increased content of anhydride units because of the radical complex mechanism of the process under these conditions.     

Polymerization of 1,3,5-trithiane in the solid state initiated by UV-irradiation. II. Investigation of the initiation process

The influence of the irradiation and polymerization atmosphere on polymer yield was observed. It was shown that in the initiation process oxygen presence is necessary. ESR studies of UV-and γ-irradiated 1,3,5-trithiane were done. The influence of the irradiation atmosphere on generated radicals and the influence of UV-action on radicals formed by γ-irradiation was also investigated. The possible initiation mechanism of cationic polymerization of 1,3,5-trithiane is discussed. A comparison of the 1,3,5-trithiane is polymerizations initiated chemically and by UV- or γ-irradiation is also given.     

Polymerization of 1,3,5-trithiane in the solid state initiated by UV-irradiation. I. Polymerization conditions and polymer characterization

The solid-state 1,3,5-trithiane polymerization initiated by UV-irradiation was studied at various irradiation times and various polymerization temperatures. The conversion of monomer to polymer reaches limiting values (at longest) in about 30 min of reaction. The apparent activation energy of this process is somewhat higher than in the chemically initiated polymerization. Generated by UV, active centers, which initiate the polymerization, are stable. On the basis of X-ray diffraction studies it was found that the prepared polythiomethylene has a hexagonal structure and high degree of crystallinity. In the polymer investigated, a new additional crystal phase is formed, which is not stable.     

Organosulphur behaviour in a GC/MS membrane interface

The behaviour of 0.1-1.0 ng amounts of S as dimethyldisulphide, n-butanethiol and diisopropylsulphide in a membrane gas-chromatograph/mass-spectrometer interface has been studied. Results are presented for an all-Teflon system which incorporated a membrane housing constructed from either glass or polymer.     

Equilibrium CH-acidities of dimethyl 2-dimethoxyphosphoryl malonate and its thiophosphoryl analog

The pK _a values of dimethyl 2-dimethoxyphosphoryl malonate and of its thiophosphoryl analog have been measured by transmetallation using the inclusion complex of Li⁺ with [2.1.1]-cryptand as the metallation agent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 410–411, February, 1993.     

A new method for the synthesis of N-substituted 1,3,5-dithiazinanes via the catalytic recyclization of 1,3,5-trithiane with aryl(benzyl) hydrazines and aryl amines

An efficient method for the synthesis of N-substituted 1,3,5-dithiazinanes based on the amination reaction of 1,3,5-trithiane with aryl(benzyl) hydrazines and N-aryl amines in the presence of Ti and Fe catalysts has been developed.     

Some periodic trends,molecular structure,normal coordinate analysis of 1,3,5-trioxane, -trithiane and -triselenane: computational and vibrational studies

The Raman (3200–100 cm⁻¹) and infrared spectra (3200–200 cm⁻¹) of solid C₃H₆O₃ (TO) and C₃H₆S₃ (TS) have been recorded and only the chair conformation is present. Furthermore, utilizing the CH stretching bands at the infrared spectrum of the gaseous phase, the CH_ax and CH_eq distances are found to be 1.088 and 1.107 Å, respectively. The structural parameters and conformational stabilities for 1,3,5-C₃H₆X₃ series (where X=O, S and Se atoms) have been obtained from density functional theory at the Becke3-LYP gradient-corrected functional (DFT-B3LYP) and from MP2 level with full electron correlation. These calculations have been extended up to 6-311++G(d,p) basis set to include polarization and diffusion functions. All computational results and vibrational analysis are in favor of the chair conformation (C_3v), whereas the boat (C₁) and Planar (D_3h) forms have been excluded owing to the predicted imaginary wavenumber(s). According to 6-311++G(d,p) basis set, the ring size and the tendency of the ring to undergo flattening is found to be directly proportional to the atomic size of the substituted hetero atoms (X) of the chair. The calculated DFT-B3LYP scaled quantum chemistry (QC) force fields at 6-31G(d) basis set lead to a number of revised assignments for certain vibrational modes and it appears to give quite accurate Raman spectra for the investigated chalcogenanes. The estimated bond lengths, bond angles, rotational constants, Raman activities dipole moment and unscaled force constants are compared with either theoretical and/or experimental results whenever possible.     

Organosulphur compounds-lxix1 optically active sulphinates: a new type of enantioselective asymmetric synthesis and kinetic resolution2

Optically active sulphinates with the sulphur atom as a sole centre at chirality are prepared by two methods. The first involves the reaction of symmetrical sulphites with tert-butylmagnesium chloride in the presence of optically active aminoalcohols. This new asymmetric, enantioselective synthesis affords t-butylsulphinates with 40–70% enantiomeric excess values. The second approach is based on a new type of kinetic resolution taking place when racemic sulphinates are reacted with tert-butylmagnesium chloride complexed by optically active alkaloid bases. Both the recovered sulphinates and sulphoxides formed in this reaction show moderate optical purities.     

Influence of a substituent at C3 on the direction of bromination of estra-1,3,5(10)trien-17-ones

The influence of a C₃ substituent on the direction of bromination of estra-1,3,5 (10)-trien-17-one is discussed: Estrone and its methyl ether give mainly derivatives bromine-substituted in ring A, while the bromination of estrone acetate leads to the production of 16-mono- and 16,16,dibromo-substituted estrones.A. Ordzhonikidze All-Union Scientific-Research Institute of Pharmaceutical Chemistry, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 327–330, May–June, 1984.     

1,3,5-Triaza-2-phosphapentalenes

Abstract

Refluxing a dialkylammonium 4,5-dicyano-1,3,2-diazaphospholate¹ with a dialkyl-amine in chloroform gives a 4,6-bis(dialkylamino)-1,3,5-triaza-2-phosphapentalene¹ in good yield as the only reaction product. Unsymmetrically substituted representatives are accessible this way too.     

Rigorous interpretation of electronic density functions of axial and equatorial conformers of dimethylphosphinoylcyclohexane, 2-(dimethylphosphinoyl)-1,3,5-trithiane, and 2-(dimethylphosphinoyl)-1,3-dithiane-1,1,3,3-tetraoxide

Theoretical analysis within the frame of the Topological Theory of Atoms in Molecules confirms the repulsive steric interaction between an axial dimethylphosphinoyl group and the syn-diaxial hydrogens in cyclohexane derivative 2-ax. In seemingly good agreement with experiment, equatorial isomer 2-eq was calculated to be 1.49 kcal/mol more stable than 2-ax. (Experimental energy difference in (diphenylphosphinoyl)cyclohexane, Delta H(o) = 1.96 kcal/mol.) In contrast, axial 2-(dimethylphosphinoyl)-1,3,5-trithiane, 3-ax, was calculated to be 6.38 kcal/mol more stable than 3-eq. (Experimentally, the axial conformer of 2-(diphenylphosphinoyl)-1,3,5-trithiane, was found to be 1.43 kcal/mol more stable than the equatorial conformer, in solvent chloroform.) Theoretical analysis, in particular the electron density at the bond critical point within the C(4,6)-H...O=P bonding trajectory, implies significant bonding in this segment of interacting atoms. By the same token, substantial positive charge is acquired by the C--H bonds adjacent to the sulfonyl groups in disulfone 4. Hydrogen bonding between the phosphoryl group and H(4,6) leads to stabilization of 4-ax, which is estimated to be 5.0 kcal/mol lower in energy than 4-eq. This conclusion is supported by examination of P==O...H--C(4,6) bond trajectories, as well as from evaluation of the critical point properties along those interacting moieties. By contrast, fluorinated derivative 5 is more stable in the equatorial conformation, indicating a repulsive electrostatic interaction of the C--F...O-P entity in 5-ax.     

Effective synthesis of <Emphasis Type="Italic">N</Emphasis>-substituted 1,3,5-dithiazinanes by reactions of <Emphasis Type="Italic">N</Emphasis>-methyl-1,3,5-dithiazinane and 1,3,5-trithiane with aromatic amines

A novel procedure has been developed for selective synthesis of N-aryl-1,3,5-dithiazinanes, 1,2,6,7-tetrahydro-3,5,1,7-benzodithiadiazonine, and 6,7-dihydro-1,3,5,7-benzotrithiazonine by reactions of aniline derivatives with N-methyl-1,3,5-dithiazinane or 1,3,5-trithiane in the presence of transition and rare earth metal salts and complexes.