Infrared-Spectroscopic Study of (4-Methylpent-3-en-1-ynyl)methylthiocarbene, Its Photochemical Transformations, and Reactions in an Argon Matrix.

Billy Bennett

The first representative of singlet carbenes bearing both ethynyl and methylthio groups at the carbene center, (4-methylpent-3-en-1-ynyl)methylthiocarbene, has been generated in a low-temperature Ar matrix upon UV photolysis of 3,3-dimethyl-5-methylthioethynyl-3H-pyrazole and detected by FTIR spectroscopy. The generation of the carbene proceeds via intermediate (3-diazo-5-methylhex-4-en-1-ynyl)methylsulfane. The comparison of FTIR spectroscopy data with the results of quantum chemical calculations (B3LYP/aug-cc-pVTZ) and NRT analysis shows that (4-methylpent-3-en-1-ynyl)methylthiocarbene has a singlet ground state with the localization of the unpaired spins on the carbon atom in the α-position to methylthio moiety.

Two major pathways of further phototransformation of the studied carbene have been found. One of them produces photochemically stable thioketone (S═CMe-C≡C-CH═CMe₂) as a result of methyl group migration from sulfur to the neighboring carbon atom, and the other one leads to the formation of labile thioketene (S═C═C(Me)-CH═CH-CMe═CH₂). Ability of (4-methylpent-3-en-1-ynyl)methylthiocarbene to insert into the H-Cl bond was established, which additionally confirms the singlet nature of this intermediate.

rac-[3-Hydroxy-6,9-dimethyl-6-(4-methylpent-3-en-1-yl)-6a,7,8,9,10,10a-hexahydro-6H-1,9-epoxybenzo[c]chromen-4-yl](phenyl)methanone.

The title compound congestiflorone, C(28)H(32)O(4), which was isolated from the stem bark of Mesua congestiflora, consists of a benzophenone skeleton with two attached pyran rings to which a cyclo-hexane ring and a C6 side chain are bonded. The benzene ring is significantly distorted from planarity (r.m.s. deviation = 0.0007 Å) due to the constraints imposed by junctions with the two pyran rings. The cyclo-hexane ring is in a chair conformation, one pyran ring is in a boat conformation, while the other is a distorted chair. The phenyl and benzene rings make a dihedral angle of 55.85 (9)°. An intra-molecular O-H⋯O hydrogen bond is observed. In the crystal, mol-ecules are linked via C-H⋯O inter-actions.

Synthesis, identification and anti-cancer activity of 1-(4-methylpent-2-enyl)-2-(4-phenylbut-2-enyl)disulfane

In this study, we synthesized 1-(4-methylpent-2-enyl)-2-(4-phenylbut-2- enyl)disulfane using sodium sulfide, 1-bromine-4-methyl-2-amylene and 1-(4-bromine-2- butylene)benzene as raw materials. The yield rate of target product was 84%. The structure of the target product was confirmed by GC-MS, 1H-NMR and elemental analysis. The results of anti-cancer activity experiments showed that 1-(4-methylpent-2-enyl)-2-(4- phenylbut-2-enyl)disulfane could significantly inhibit the proliferation, induce the apoptosis of CNE2 cells in a dose dependent manner, and could significantly enhance the activity of XIAP.

Synthesis and antitumor activity of 6- and 2-(1-substituted-thio-4-methylpent-3-enyl)-5,8-dimethoxynaphthalene-1,4-diones

In an attempt to develop potent and selective antitumor agents, a series of 6- and 2-(1-substituted-thio-4-methylpent-3-enyl)-5,8-dimethoxynaphthalene-1,4-diones were designed and synthesized. The cytotoxicities of these compounds were evaluated in vitro against BEL-7402, HT-29 and SPC-A1 cell lines. The pharmacological results showed that most of the prepared compounds displayed the excellent selective cytotoxicity toward HT-29 cells. From the structure-activity relationships we may conclude that the introduction of a thioether functional group at the 1′-position in the side chain of shikonin is associated with an increase in cytotoxicity.

Gas-phase rate coefficients for the reactions of nitrate radicals with (Z)-pent-2-ene, (E)-pent-2-ene, (Z)-hex-2-ene, (E)-hex-2-ene, (Z)-hex-3-ene, (E)-hex-3-ene and (E)-3-methylpent-2-ene at room temperature.

Rate coefficients for reactions of nitrate radicals (NO3) with (Z)-pent-2-ene, (E)-pent-2-ene, (Z)-hex-2-ene, (E)-hex-2-ene, (Z)-hex-3-ene, (E)-hex-3-ene and (E)-3-methylpent-2-ene were determined to be (6.55 +/- 0.78)x 10(-13) cm3 molecule(-1) s(-1), (3.78 +/- 0.45)x 10(-13) cm3 molecule(-1) s(-1), (5.30 +/- 0.73)x 10(-13) cm(3) molecule(-1) s(-1), (3.83 +/- 0.47)x 10(-13) cm(3) molecule(-1) s(-1), (4.37 +/- 0.49)x 10(-13) cm(3) molecule(-1) s(-1), (3.61 +/- 0.40)x 10(-13) cm3 molecule(-1) s(-1) and (8.9 +/- 1.5)x 10(-12) cm3 molecule(-1) s(-1), respectively. We performed kinetic experiments at room temperature and atmospheric pressure using a relative-rate technique with GC-FID analysis.

The experimental results demonstrate a surprisingly large cis-trans(Z-E) effect, particularly in the case of the pent-2-enes, where the ratio of rate coefficients is ca. 1.7. Rate coefficients are discussed in terms of electronic and steric influences, and our results give some insight into the effects of chain length and position of the double bond on the reaction of NO3 with unsaturated hydrocarbons. Atmospheric lifetimes were calculated with respect to important oxidants in the troposphere for the alkenes studied, and NO3-initiated oxidation is found to be the dominant degradation route for (Z)-pent-2-ene, (Z)-hex-3-ene and (E)-3-methylpent-2-ene.

Assessment of bioremediation possibilities of technical grade hexachlorocyclohexane (tech-HCH) contaminated soils.

Hexachlorocyclohexane (HCH) is a broad spectrum insecticide still used in some of the developing countries, though developed countries have banned or curtailed its use. Even in those countries where the use of t-HCH has been discontinued for a number of years, the problem of residues of all isomers of t-HCH remains because of its high persistence. These insecticides in the soil disturb the delicate equilibrium between microorganisms and their environment. Few reports on the degradation of t-HCH isomers in soil are present in literature, and very little information is available on the effect of these t-HCH isomers on soil microflora.

In the present study, an attempt has been made to see the microbial diversity in the uncontaminated soils and the effect of application of t-HCH on the soil microflora. The soil was spiked with t-HCH and incubated, at regular time intervals the soil samples were analyzed for microbial diversity as well as t-HCH isomers residues. The results show that at higher concentrations of t-HCH, microbial populations were inhibited and the inhibited populations did not reappear even after prolonged incubation. Potential t-HCH degrading cultures were isolated and subjected to further acclimation in order to enhance their degradation capacity. The results are presented and discussed in this paper.

Suitability of thermal plasma for solid waste treatment and non-thermal plasma for nano-scale high-tech plasmonic materials: a concise review

In the recent past, plasma waste technology has emerged to be an environmental friendly and beneficial technology. In this review, current status of thermal plasma, non-thermal plasma and its application for nano-scale high-tech plasmonic materials based on the scientific and technical comprehensive observation are included. Generally, thermal plasma is used for solid waste treatment but non-thermal plasma is being utilized for plasmonic materials. The current research incorporated in two phases: thermal plasma and non-thermal plasma. In the first phase, understanding and detailed information about plasma torches have been included such as DC transfer and non-transfer arc plasma torches.

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In addition, solid waste treatment, municipal waste, healthcare issue, steel making and treatment through plasma jet injection have been reviewed extensively. In the second phase, state-of-the-art review has been addressed for dielectric barrier discharge (DBD) and its utility for plasmonic materials. The analysis concluded that the thermal plasma is the optimal choice for treating solid waste issues and the application of non-thermal plasma such as DBD is the most useful and latest approach for plasmonic material. The prime objective of this review is not only to provide the comparison between thermal or non-thermal plasma but to recommend the ideal and most optimized suitable technique for solid waste treatment and bio-medical applications.