Claude Lion

Synthesis, antioxidant properties and radioprotective effects of new benzothiazoles and thiadiazoles

In this work, we report the synthesis and characterization of new compounds derived from benzothiazoles and thiadiazoles. We observed that structural modifications on these skeletons affected the antioxidant activity. Thiol and aminothiol compounds derived from thiadiazoles and benzothiazoles showed an interesting antioxidant property. The radioprotective activity has also been evaluated in mice. Some of these compounds could be good radioprotectors.

Pathways of photocatalytic gas phase destruction of HD simulant 2-chloroethyl ethyl sulfide

Abstract Photocatalytic oxidation of HD simulant, 2-chloroethyl ethyl sulfide (CEES), was studied in a specially designed coil and flow photocatalytic reactor by means of GC-MS and FTIR techniques. TiO 2 Hombikat UV 100 photocatalyst was deactivated after a few hours of operation, which was signaled by the appearance of incomplete oxidation products in the reactor effluent and accumulation of incomplete oxidation products on the TiO 2 surface. Complete reactivation of the photocatalyst was achieved by washing the photocatalyst with water. Compared to diethyl sulfide, CEES showed lower reactivity in photocatalytic oxidation and was accumulated on the TiO 2 surface after catalyst deactivation. Without UV irradiation, hydrolysis of CEES proceeded on the TiO 2 surface. Major gaseous products of CEES incomplete photocatalytic oxidation are acetaldehyde, chloroacetaldehyde, SO 2 , diethyl disulfide, and chloroethylene. Surface products extracted from the TiO 2 surface with acetonitrile and water include mainly 2-chloroethyl ethyl sulfoxide and ethanesulfinic and ethanesulfonic acids, as well as diethyl di-, tri-, and tetrasulfides mono and disubstituted in the β position with a chlorine or hydroxyl group. While surface monodentate sulfates can be removed upon washing, surface bidentate species stayed on the surface and possibly contribute to the permanent catalyst deactivation.

Routes of photocatalytic destruction of chemical warfare agent simulants

Selected imitants of chemical warfare agents such as dimethyl methylphosphonate (DMMP), diethyl phosphoramidate (DEPA), pinacolyl methylphosphonate (PMP), butylaminoethanethiol (BAET) were subjected to photocatalytic and sonophotocatalytic treatment in aqueous suspensions of TiO2. Complete conversion of the same mass of imitants to inorganic products was obtained within 600 min for DMMP, DEPA, PMP, but required a longer time for BAET. Sonolysis accelerated photodegradation of DMMP. No degradation was observed without ultraviolet illumination. Final products of degradation were PO43−, CO2 for DMMP and PMP, PO43−, NO3− (25%), NH4+ (75%), CO2 for DEPA, and SO42−, NH4+, CO2 for BAET. The number of main detected intermediate products increases in the order DMMP (7), DEPA (9), PMP (21), and exceeds 34 for BAET. Degradation of DMMP mainly proceeds through consecutive oxidation of methoxy groups and then the methyl group. Dimethyl hydroxymethylphosphonate and dimethylphosphate testify to the parallel oxidation of the methyl group. Destruction of DEPA mainly starts with cleavage of the P–NH2 bond to form diethyl phosphate, which transforms further into ethyl phosphate. Oxidation of α and β carbons of ethoxy groups to form ethylphosphonoamidate, hydroxyethyl ethylphosphonoamidate and other products also contributes to the destruction. Photocatalytic degradation of PMP mainly starts with oxidation of the pinacolyl fragment, methylphosphonic acid and acetone being the major products. Oxidation of BAET begins with dark dimerization to disulfide, which undergoes oxidation of sulfur forming sulfinic and sulfonic acids as well as oxidation of carbons to form butanal, aminobutane, etc., and cyclic products such as 2-propylthiazole. A scheme of degradation was proposed for DMMP and DEPA, and starting routes for PMP and BAET. Quantum efficiencies of complete mineralization calculated as reaction rate to photon flux ratio approximate 10−3%.

TiO2 reactivation in photocatalytic destruction of gaseous diethyl sulfide in a coil reactor

Abstract Diethyl sulfide (DES) photocatalytic oxidation was carried out in a flow research reactor with TiO2 Hombikat UV 100 deposited onto the internal surface of a Pyrex coil. The reactor allowed easy catalyst reactivation by washing with water. Mass transfer limitations were not detected in the reactor. Catalyst deactivated after several hours of complete DES mineralization, which was expressed by decrease of effluent CO2 concentration and appearance of gaseous intermediates. Catalyst reactivation was achieved by two procedures: (1) irradiating photocatalyst until complete mineralization of adsorbed organic products with subsequent water washing; and (2) immediate washing with water. The water used after the first procedure contained only H2SO4, while after the second procedure it contained organic intermediates. The second procedure was much faster. Lower water concentration and higher catalyst loading allowed longer catalyst stability in DES oxidation. Low feed DES concentration resulted in much longer deactivation. Twelve consecutive runs were done to test reactivation completeness. Some permanent catalyst deactivation was noted and explained by TiO2 etching with H2SO4. Gaseous and surface intermediate products were detected in the reactor effluent and catalyst wash water using solid phase microextraction (SPME) and trimethylsilyl derivatization. Main gaseous products were acetaldehyde, diethyl disulfide, ethylene, SO2, and main surface products were diethyl disulfide, diethyl trisulfide, 1,2-bis(ethylthio)ethane, ethanesulfinic, ethanesulfonic acids, diethyl sulfoxide, diethyl sulfone, and sulfuric acid.

Electrosynthesis and photoisomerization of a new fluorescent aromatic polymer bearing a pendant substituted norbornadiene group

Fluorescent polyphenylene films bearing a norbornadiene (NBD) substituent are electrosynthesized for the first time, and the photoisomerization kinetics of the pendant NBD group are investigated.

Synthèse et activité radioprotectrice de germatranes, silatranes, oxydes et sulfures germaniés à ligande chlorhydrate de cystéamine, méthylcystéamine et N(thio-2 éthyl)diamino-1,3 propane

Resume De nouvelles structures organogermaniees et siliciees de type germatranes ou silatranes, oxydes ou sulfures de germanium a ligande chlorhydrate de cysteamine, de methylcysteamine et N (thio-2 ethyl)diamino-1,3 propane, ont ete synthetisees. Leur toxicite aigue et leur activite radioprotectrice ont ete determinees. Les germatranes semblent etre les structures les plus actives dans ce dernier domaine. La toxicite de ces derives (y compris celle des silatranes) est generalement faible.

Gas—liquid chromatographic retention behaviour of hindered aliphatic esters

Abstract Relative retentions and Kovats retention indices of sixteen crowded aliphatic ethyl or methyl esters (R 1 R 2 CHCO 2 R or R 1 R 2 R 3 CCO 2 R; R = ethyl or methyl) have been systematically determined on nine stationary phases of increasing polar character from the non-polar branched-chain hydrocarbon C 87 H 176 to the highly polar cyanopropylsiloxane Silar–10C. A qualitative pattern showing the retention behaviour of the branched acyl group of the esters is developed. An unexpectedly strong contribution of polar effect occurs with highly congested acyl groups in α,α,α-trialkyl esters.

Synthèse et activité radioprotectrice de nouveaux trithiagermatranes, trithiasilatranes, oxyde et sulfure germaniés à substituant chlorhydrate de cystéamine et N(2-thioéthyl)-1,3-diaminopropane

Resume De nouvelles structures organogermaniees et siliciees des types: trithiagermatranes ou trithiasilatranes, bicyclodithiazagermolidines et 6-aza, 1,3-dithia, 2-germaperhydrocines a ligands chlorhydrates de cysteamine et de N(2-thioethyl)-1,3-diaminopropane et oxyde ou sulfure de germanium a substituant chlorhydrate de N(2-thioethyl)-1,3-diaminopropane ont ete synthetisees. Leur toxicite aigue et leur activite radioprotectrice ont ete determinees.

Synthesis and antioxidant properties of pulvinic acids analogues

The synthesis of three types of pulvinic acid analogues, using a diversity-oriented strategy starting from a single compound, dimethyl l-tartrate, is described. Lacey-Dieckmann condensation, alcohol dehydration and Suzuki-Miyaura cross-couplings were employed in the course of the analogues syntheses. The evaluation of the antioxidant properties of the 28 synthesized analogues was carried out using antioxidant capacity assays (protection of thymidine and β-carotene) and free radical scavenging assays (DPPH radical and ABTS radical cation). This allowed to assess the relative influence of the groups bonded to the tetronic ring and to the exocyclic double bond on the activity, as well as the importance of this exocyclic double bond. It was shown that the presence of an electron-donating group on the 3-position of the tetronic ring had a beneficial effect. It was shown in several assays that the presence of the exocyclic bond was not crucial to the activity.

A REVIEW ON THE RADIOPROTECTIVE ACTIVITY OF ORGANOGERMANIUM AND ORGANOSILICON COMPOUNDS

The present review describes the work carried out during the last 20 years in the field of the radioprotective activity and toxicity of several classes of organosilicon and organogermanium compounds (i.e. metallathiazolidines, metalladithioacetals, metallatranes and germathianes).