Reactions of polyhalogenated aromatic compounds and related ethers with metal/ammonia solutions

This work contains the results of a series of reduction studies on polyhalogenated aromatic compounds and related ethers using alkali metals in liquid ammonia. In general, polychlorobenzenes were reduced to t he parent aromatic hydrocarbon or to 1 ,4-cyc1ohexadiene, and dipheny1ethers were cleaved to the aroma tic hydrocarbon and a phenol. Chlorinated dipheny1ethers were r eductive1y dechlorinated in the process. For example, 4-chlorodipheny1- ether gave benzene and phenol. Pentach1orobenzene and certain tetrachlorobenzenes disproportionated to a fair degree during the reduction process if no added proton source was present. The disproportionation was attributed to a build-up of amide ion. Addition of ethanol completely suppressed the formation of any disproportionation products. In the reductions of certain dipheny1ethers , the reduction of one or both of the dipheny1ether rings occurred, along with the normal cleavage. This was more prevalent when lithium was the metal used . As a Sidelight, certain chloropheno1s were readily dechlorinated. In light of these results, the reductive detoxification of the chlorinated dibenzo-1,4-dioxins seems possible with alkali metals in l iquid ammonia.

Biotransformation of aromatic hydrocarbons and organic sulphides by fungi

Toluene is converted to benzyl alcohol by the fungi Mortierella isabellina and Helminthosporium species; in the latter case, the product is further metabolized. Toluene-a -d 1 , toluene-a,a-d2, and toluene-a,a,a-d 3 have been used with Mortierellaisabellina in a series of experiments to determine both primary and secondary deuterium kinetic isotope effects for the enzymic benzylic hydroxylation reaction. The values obtained, intermolecular primary kH/kD = intramolecular p rim a r y kH r kD = 1. 0 2 + O. 0 5, and sec 0 n dar y k H I kD = 1. 37 .:!. 0.05, suggest a mechanism for the reaction involving benzylic proton removal from a radical intermediate in a non-symmetrical transition state. 2H NMR (30.7 MHz) studies using ethylbenzene-l,1-d 2 , 3 -fluoroethylbenzene-l,1-d 2 , 4 -fluoroethylbenzene-l,1-d 2 , and toluene-dB as substrates with Mortierella isabellina suggest, based on the observable differences in rates of conversion between the substrates, that the hydroxylation of hydrocarbons at the benzylic position proceeds via a one electron abstraction from the aromatic ring, giving a radical cation. A series of 1,3-oxathiolanes (eight) were incubated with Mortierella isabellina , Helminthosporium , Rhizopus arrhizus , and Aspergillus niger . Sulphoxides were obtained from Mortierella isabellina and Rhizopus arrhizus using the substrates 2-phenyl-, 2-methyl-2-phenyl-, and 2-phenyl-2-tert. butyl-l,3-oxathiolane. The relative stereochemistry of 2-methyl-2-phenyl-l,3-oxathiolan-l-oxide was assigned based on lH decoupling, n.O.e, 1 and H NMR experiments. The lH NMR (200 MHz) of the methylene protons of 2-methyl-2-phenyl-l,3-oxathiolan-l-oxide was used as a diagnostic standard in assigning the relative stereochemistry of 2-phenyl-l,3-oxathiolan-l-oxide and 2-phenyl-2-tert. butyl-l,3-oxathiolan-l-oxide. The sulphoxides obtained were consistent with an oxidation occurring from the opposite side of the molecule to the phenyl substituent.

Reactions of various aromatic nitro-compounds and anthraquinones with selected bases and nucleophiles

The Introducti on deals mainly with hi storical studies on aryne chemi stry and ring closure via arynes , hydride replacement from aromatic rings by nucleophi les, c l eavage of anthr aquinones in basic medium and the Leuckart reaction . This work can be divided into two main s ect i ons. Section I is concerned with the investigation of t he reaction of some aromatic ni t ro-compounds with potassamide in l iquid ammonia. 3-Amino-4- nitrobenzophenone was obtained from the reacti on of 4-nitrobenzophenone with t his reagent, toge t her with benzoic acid formed in a competing Haller-Bauer reaction. Nitrobenzene under these conditions gave a complex mixture from which 2-phenylphenol was isolated; a reaction i nvolving benzyne may be i nvo l ved. 4-Nitrodiphenyl sulfone gave 4-aminodiphenyl sulfone and 4-nitroani l ine. 4-Ethoxydiphenyl sulfone and 4-ethoxynitrobenzene were isolated when ethanol was used as a co-solvent in the reaction. Oxidative coupling reactions were observed with nitrotoluenes. 4-Nitrotoluene gave 4,4t-dinitrobibenzyl which i n a pro longed reaction gave 4,4t-dinitros t ilbene . 2-Nitrotoluene gave 2 , 2 t-dinitrobibenzyl, but not the corresponding stilbene derivative even after a longer time . A rather i nteresting result was obtained with 1-nitro-2,4,6- trimethylbenzene which gave a stilbene derivative only. Also the corresponding stilbene was obtained from bis-(4-nitrophenyl)-methane in a rather slow r eaction with this reagent . Section II deals wi th (i) the preparation of 5-chloro- 1-N-methyl aminoanthraquinone and a new synthesis of N-methyl acridones and (ii) treatment of chloro-anthraquinones with fo rmamide and a new synthesis of chloro-anthracenes . 5-Chloro-1 -N-methylaminoanthraqui none was synthesised f rom 1,5-dichloroanthraquinone by treatment with N-methylformamide. Treatment of 5-chloro-1-N-methylaminoanthraquinone with potassamide in liquid ammonia or with potassium t-butoxide i n t-butylbenzene gave N-methylacridone-1-carboxylic acid. This pleasing result, t he outcome of r i ng opening and alter native ring closure, is being extended to related ring systems.

Investigations into the determination of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) by capillary gas chromatography

Factors involved in the determination of PAHs (16 priority PAHs as an example) and PCBs (10 PCB congeners, representing 10 isomeric groups) by capillary gas chromatography coupled with mass spectrometry (GC/MS, for PAHs) and electron capture detection (GC/ECD , for PCBs) were studied, with emphasis on the effect of solvent. Having various volatilities and different polarities, solvent studied included dichloromethane, acetonitrile, hexan e, cyclohexane, isooctane, octane, nonane, dodecane, benzene, toluene, p-xylene, o-xylene, and mesitylene. Temperatures of the capillary column, the injection port, the GC/MS interface, the flow rates of carrier gas and make-up gas, and the injection volume were optimized by one factor at a time method or simplex optimization method. Under the optimized conditions, both peak height and peak area of 16 PAHs, especially the late-eluting PAHs, were significantly enhanced (1 to 500 times) by using relatively higher boiling point solvents such as p-xylene and nonane, compared with commonly used solvents like benzene and isooctane. With the improved sensitivity, detection limits of between 4.4 pg for naphthalene and 30.8 pg for benzo[g,h,i]perylene were obtained when p-xylene was used as an injection solvent. Effect of solvent on peak shape and peak intensity were found to be greatly dependent on temperature parameters, especially the initial temperature of the capillary column. The relationship between initial temperature and shape of peaks from 16 PAHs and 10 PCBs were studied and compared when toluene, p-xylene, isooctane, and nonane were used as injection solvents. If a too low initial temperature was used, fronting or split of peaks was observed. On the other hand, peak tailing occurred at a too high initial column temperature. The optimum initial temperature, at which both peak fronting and tailing were avoided and symmetrical peaks were obtained, depended on both solvents and the stationary phase of the column used. On a methyl silicone column, the alkane solvents provided wider optimum ranges of initial temperature than aromatic solvents did, for achieving well-shaped symmetrical GC peaks. On a 5% diphenyl: 1% vinyl: 94% dimethyl polysiloxane column, when the aromatic solvents were used, the optimum initial temperature ranges for solutes to form symmetrical peaks were improved to a similar degree as those when the alkanes were used as injection solvents. A mechanism, based on the properties of and possible interactions among the analyte, the injection solvent, and the stationary phase of the capillary column, was proposed to explain these observations. The effect of initial temperature on peak height and peak area of the 16 PAHs and the 10 PCBs was also studied. The optimum initial temperature was found to be dependent on the physical properties of the solvent used and the amount of the solvent injected. Generally, from the boiling point of the solvent to 10 0C above its boiling point was an optimum range of initial temperature at which cthe highest peak height and peak area were obtained.

Gas chromatographic electron capture negative ionization mass spectrometric (GC/ECNI/MS) determination of unique fluorinated compounds in the sediments of Lake Ontario and the effect of high-boiling alcohols (as injection solvents) on chromatographic behaviour of polycyclic aromatic hydrocarbons in gas chromatography

Part I - Fluorinated Compounds A method has been developed for the extraction, concentration, and determination of two unique fluorinated compounds from the sediments of Lake Ontario. These compounds originated from a common industrial landfill, and have been carried to Lake Ontario by the Niagara River. Sediment samples from the Mississauga basin of Lake Ontario have been evaluated for these compounds and a depositional trend was established. The sediments were extracted by accelerated solvent extraction (ASE) and then underwent clean-up, fractionation, solvent exchange, and were concentrated by reduction under nitrogen gas. The concentrated extracts were analyzed by gas chromatography - electron capture negative ionization - mass spectrometry. The depositional profile determined here is reflective of the operation of the landfill and shows that these compounds are still found at concentrations well above background levels. These increased levels have been attributed to physical disturbances of previously deposited contaminated sediments, and probable continued leaching from the dumpsite. Part II - Polycyclic Aromatic Hydrocarbons Gas chromatography/mass spectrometry is the most common method for the determination of polycyclic aromatic hydrocarbons (PAHs) from various matrices. Mass discrimination of high-boiling compounds in gas chromatographic methods is well known. The use of high-boiling injection solvents shows substantial increase in the response of late-eluting peaks. These solvents have an increased efficiently in the transfer of solutes from the injector to the analytical column. The effect of I-butanol, I-pentanol, cyclopentanol, I-hexanol, toluene and n-octane, as injection solvents, was studied. Higher-boiling solvents yield increased response for all PAHs. I -Hexanol is the best solvent, in terms of P AH response, but in this solvent P AHs were more susceptible to chromatographic problems such as peak splitting and tailing. Toluene was found to be the most forgiving solvent in terms of peak symmetry and response. It offered the smallest discrepancies in response, and symmetry over a wide range of initial column temperatures.

High-Spin and Emissive Molecular Materials: Synthesis and Characterization of New Polynuclear Ni(II) Complexes from the Use of Aromatic Schiff Bases as Bridging Ligands

The employment of the bridging/chelating Schiff bases, N-salicylidene-4-methyl-o-aminophenol (samphH2) and N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in nickel cluster chemistry has afforded eight polynuclear Ni(II) complexes with new structural motifs, interesting magnetic and optical properties, and unexpected organic ligand transformations. In the present thesis, Chapter 1 deals with all the fundamental aspects of polynuclear metal complexes, molecular magnetism and optics, while research results are reported in Chapters 2 and 3. In the first project (Chapter 2), I investigated the coordination chemistry of the organic chelating/bridging ligand, N-salicylidene-4-methyl-o-aminophenol (samphH2). The general NiII/tBuCO2-/samphH2 reaction system afforded two new tetranuclear NiII clusters, namely [Ni4(samph)4(EtOH)4] (1) and [Ni4(samph)4(DMF)2] (2), with different structural motifs. Complex 1 possessed a cubane core while in complex 2 the four NiII ions were located at the four vertices of a defective dicubane. The nature of the organic solvent was found to be of pivotal importance, leading to compounds with the same nuclearity, but different structural topologies and magnetic properties. The second project, the results of which are summarized in Chapter 3, included the systematic study of a new optically-active Schiff base ligand, N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in NiII cluster chemistry. Various reactions between NiX2 (X- = inorganic anions) and nacbH2 were performed under basic conditions to yield six new polynuclear NiII complexes, namely (NHEt3)[Ni12(nacb)12(H2O)4](ClO4) (3), (NHEt3)2[Ni5(nacb)4(L)(LH)2(MeOH)] (4), [Ni5(OH)2(nacb)4(DMF)4] (5), [Ni5(OMe)Cl(nacb)4(MeOH)3(MeCN)] (6), (NHEt3)2[Ni6(OH)2(nacb)6(H2O)4] (7), and [Ni6(nacb)6(H2O)3(MeOH)6] (8). The nature of the solvent, the inorganic anion, X-, and the organic base were all found to be of critical importance, leading to products with different structural topologies and nuclearities (i.e., {Ni5}, {Ni6} and {Ni12}). Magnetic studies on all synthesized complexes revealed an overall ferromagnetic behavior for complexes 4 and 8, with the remaining complexes being dominated by antiferromagnetic exchange interactions. In order to assess the optical efficiency of the organic ligand when bound to the metal centers, photoluminescence studies were performed on all synthesized compounds. Complexes 4 and 5 show strong emission in the visible region of the electromagnetic spectrum. Finally, the ligand nacbH2 allowed for some unexpected organic transformations to occur; for instance, the pentanuclear compound 5 comprises both nacb2- groups and a new organic chelate, namely the anion of 5-chloro-2-[(3-hydroxy-4-oxo-1,4-dihydronaphthalen-1-yl)amino]benzoic acid. In the last section of this thesis, an attempt to compare the NiII cluster chemistry of the N-naphthalidene-2-amino-5-chlorobenzoic acid ligand with that of the structurally similar but less bulky, N-salicylidene-2-amino-5-chlorobenzoic acid (sacbH2), was made.

Ring-opening of cycloalkane epoxides and aziridines with aromatic amines : toward the total synthesis of pactamycin

Résumé Cette thèse consiste en trois thèmes résumés dans les paragraphes ci-dessous. L’influence de différents groupements protecteurs du groupe hydroxyle lors des réactions d’ouverture des cis- et trans- 3-hydroxy-1,2-époxycycloalcanes a été étudiée. Il a été montré que Yb(OTf)3 constituait un catalyseur doux pour l’ouverture régiosélective de cycles afin d’obtenir les -anilino cycloalcanols correspondants avec de bons rendements. Le chauffage du milieu réactionnel dans le toluène comme solvant a permis d’augmenter la cinétique de la réaction, au dépend du rendement. La partie aniline a été régiosélectivement introduite en position vicinale du groupe hydroxyle ou éther afin d’obtenir un unique régioisomère. La même tendance a été observée avec les époxydes du 3-azidocyclohex-1-ène et du 3-carbamate correspondant. Le temps de réaction a été réduit lorsque Yb(OTf)3 a été dissous dans l’acétonitrile. Le triflate d’ytterbium (III) a également été utilisé comme catalyseur pour l’ouverture de cycle régiosélective d’aziridines non-activées sur des cyclohexanes portant des substituants azotures ou éthers de benzyle. L’ion azoture ou l’aniline forment les produits trans correspondants, donnant alors accès à des diamines vicinales avec de bons rendements. Un éther ω-alcoxy p-méthoxybenzylique racémique, inhibiteur de HDAC, a été ainsi préparé en huit étapes synthétiques (rendement total de 26%) à partir du 1-((tert-butyldiphénylsilyl)oxy)hept-6-èn-2-ol. Ceci représente un progrès par rapport à la précédente méthode (9 étapes, rendement total de 16%). La métathèse croisée se montre particulièrement efficace et pratique dans cette stratégie et l’alkylation par le trichloroacétimidate de p-méthoxybenzyle en présence de Sc(OTf)3 améliore le rendement global de la synthèse. Un aminoalcool présent dans la pactamycine et contenant le squelette carboné, les groupements fonctionnels et la stéréochimie requise a été synthétisé en 27 étapes à partir de la L-thréonine. La méthodologie décrite dans cette thèse permet la synthèse de cet intermédiaire clé à l’échelle multigramme.

Carbon-carbon bond formation : from transition metal catalysis to base-promoted homolytic aromatic substitution

Cette thèse de doctorat porte sur la catalyse à partir de métaux de transition et sur la substitution homolytique aromatique favorisée par une base visant à former de nouvelles liaisons C–C, et à ainsi concevoir de nouvelles structures chimiques. Au cours des vingt dernières années, des nombreux efforts ont été réalisés afin de développer des méthodologies pour la fonctionnalisation de liens C–H, qui soient efficaces et sélectives, et ce à faible coût et en produisant le minimum de déchets. Le chapitre d'introduction donnera un aperçu de la fonctionnalisation directe de liens C–H sur des centres sp2 et sp3. Il sera également discuté dans cette partie de certains aspects de la chimie radicalaire reliés a ce sujet. Les travaux sur la fonctionnalisation d’imidazo[1,5-a]pyridines catalysée par des compleces de ruthénium seront présentés dans le chapitre 2. Malgré l'intérêt des imidazo[1,5-a]azines en chimie médicinale, ces composés n’ont reçu que peu d'attention dans le domaine de la fonctionnalisation de liens C–H. L'étendue de la réaction et l'influence des effets stériques et électroniques seront détaillés. Les cyclopropanes représentent les 10ème cycles carbonés les plus rencontrés dans les petites molécules d’intérêt pharmacologique. Ce sont aussi des intermédiaires de synthèse de choix pour la création de complexité chimique. Malgré de grands progrès dans le domaine de la fonctionnalisation de liens C(sp3)–H, l'étude des cyclopropanes comme substrats dans les transformations directes est relativement nouvelle. Le chapitre trois présentera l'arylation intramoléculaire directe de cyclopropanes. Cette réaction est réalisée en présence de palladium, en quantité catalytique, en combinaison avec des sels d’argent. Des études mécanistiques ont réfuté la formation d'un énolate de palladium et suggéreraient plutôt une étape de métallation - déprotonation concertée. En outre, les cycles de type benzoazepinone à sept chaînons ont été synthétisés par l'intermédiaire d'une séquence d'activation de cyclopropane/ouverture/cyclisation. Une arylation directe intermoléculaire des cyclopropanes a été réalisée en présence d'un auxiliaire de type picolinamide (Chapitre 4). Les deux derniers chapitres de ce mémoire de thèse décriront nos études sur la substitution homolytique aromatique favorisée par une base. Le mécanisme de la réaction de cyclisation intramoléculaire d'halogénures d'aryle, réalisée en présence de tert-butylate de potassium, a été élucidé et se produit via une voie radicalaire (Chapitre 5). La transformation, exempte de métaux de transition, ne nécessite que la présence d’une base et de pyridine comme solvant. Cette réaction radicalaire a été étendue à la cyclisation d'iodures d'alkyle non activés en présence d'un catalyseur à base de nickel et de bis(trimethylsilyl)amidure de sodium comme base (Chapitre 6). Des études de RMN DOSY ont démontré une association entre le catalyseur, la base et le matériel de départ.

Polycyclic aromatic hydrocarbons and toxic trace metals in seawater and sediments from the west coast of India and their bioaccumulation in some selected species of fishes

Polycyclic Aromatic Hydrocarbons and other toxic compounds from industrial effluents are noted for their high potency for skin, lung, bladder and gastrointestinal cancers. Increased industrialization, and population growth led to greater production of wastes, Pesticides and PAHs have received attention due to their carcinogenic effects. The main objectives of the study were; to collect base line data on the concentration of PAHs in seawater and sediment from the west coast of India, the concentration of PAHs in certain species of fishes, the comparative levels of PAHs in fish, the influence of sediment characteristics on the concentration of PAH in sediment, changes in PAH concentration in water, sediment and fish, to provide a base line concentration of trace metals in water, sediment and fish, the seasonal changes in content of selected trace metals in water, sediment and fish from the west coast of India. The present study revealed that a predominance of silt and clay at all stations in the off Cochin area. The study has provided comprehensive information available to date for PAHs in seawater, sediment and fishes from the west cost of India especially from the Quilon to Mangalore region.

Distribution of Polycyclic Aromatic Hydrocarbons in the Cochin Estuary and Backwaters

Department of Chemical Oceanography,Cochin University of Science and Technology

Studies on the effect of Polycyclic Aromatic Hydrocarbons in the life and activity of Perna spp

In the present study an endeavour has been made to analyse the acute toxicity of WAFs of Bombay High crude and Light Diesel oil on commercially important bivalve species Perna viridis and Perna indica by static bioassay methods. The toxic effects of chemicals in the WAF on the organisms ; their tissues and eventually on rate functions have been elucidated. Marine oil pollution not only affects productivity and quality of marine organisms but also eventually affects the health of human population due to a possible health risk by way of consumption of oil contaminated seafood

Erratum: "The aromatic fluctuation index (FLU): a new aromaticity index based on electron delocalization" [J. Chem Phys. 122, 014109 (2005)]

An erratum to the article "The aromatic fluctuation index (FLU): a new aromaticity index based on electron delocalization", published in The Journal Chemistry of Physics, 2005, v.122, art. no.014109. Values FLU have been corrected in the last column of Table I because they were not correct

The aromatic fluctuation index (FLU): a new aromaticity index based on electron delocalization

In this work, the aromatic fluctuation index (FLU) that describes the fluctuation of electronic charge between adjacent atoms in a given ring is introduced as a new aromaticity measure. This new electronic criterion of aromaticity is based on the fact that aromaticity is related to the cyclic delocalized circulation of π electrons. It is defined not only considering the amount of electron sharing between contiguous atoms, which should be substantial in aromatic molecules, but also taking into account the similarity of electron sharing between adjacent atoms. For a series of rings in 15 planar polycyclic aromatic hydrocarbons, we have found that, in general, FLU is strongly correlated with other widely used indicators of local aromaticity, such as the harmonic-oscillator model of aromaticity, the nucleus independent chemical shift, and the para-delocalization index (PDI). In contrast to PDI, the FLU index can be applied to study the aromaticity of rings with any number of members and it can be used to analyze both the local and global aromatic character of rings and molecules