Photofragmentation Reactions Of Thiocarbonyl Compounds

Preferential yield of ring expansion and rearrangement products through α-cleavage of tetramethyl-3-thio-1,3-cyclobutanedione (1) and 3-mercapto-2,2,4-trimethyl-3-pentenoic acid β-(thio lactone) (2) involving diradical and carbene has been observed upon photolysis of 1 and 2.

WISENOM. A formal organic chemical nomenclature system

A formal chemical nomenclature system WISENOM based on a context-free grammar and graph coding is described. The system is unique, unambiguous, easily pronounceable, encodable, and decodable for organic compounds. Being a formal system, every name is provable as a theorem or derivable as a terminal sentence by using the basic axioms and rewrite rules. The syntax in Backus-Naur form, examples of name derivations, and the corresponding derivation trees are provided. Encoding procedures to convert connectivity tables to WISENOM, parsing, and decoding are described.

Facile conversion of electron rich benzylic hydrocarbons to carbonyl compounds by peroxydisulphate and copper ions

A convenient method for the conversion of electron rich benzylic hydrocarbons to carbonyl compounds is reported.

Electron-Energy Loss Spectroscopy (Eels) Of Organic-Molecules In Vapor-Phase - Design And Fabrication Of An Indigenous Eel Spectrometer

An indigenous electron energy loss spectrometer has been designed and fabricated for the study of free molecules. The spectrometer enables the recording of low-resolution electronic spectra of molecules inthe vapour phase with ready access to the vacuum ultraviolet region. Electron energy loss spectra of aliphatic alcohols and carbonyl compounds as wellas of benzene derivatives have been recorded with the indigenous spectrometer and the electronic transitions in these molecules discussed.

Metal-organic framework structures - how closely are they related to classical inorganic structures?

Metal-organic frameworks (MOFs) have emerged as an important family of compounds for which new properties are increasingly being found. The potential for such compounds appears to be immense, especially in catalysis, sorption and separation processes. In order to appreciate the properties and to design newer frameworks it is necessary to understand the structures from a fundamental perspective. The use of node, net and vertex symbols has helped in simplifying some of the complex MOF structures. Many MOF structures are beginning to be described as derived from inorganic structures. In this tutorial review, we have provided the basics of the node, the net and the vertex symbols and have explained some of the MOF structures. In addition, we have also attempted to provide some leads towards designing newer structures/topologies.

Chlorine-35 Nuclear Quadrupole Resonance Studies in 2,3- and 3,5-Dichloroanisoles

The temperature variation of the 3’Cl n.q.r. frequencies in 3,5- and 2,3- dichloroanisoles has been reported here. Both compounds show two lines each, and these have been assigned to the two chlorines in the same molecule with the help of the additive model for the substituent effect. The temperature dependence has been analysed in terms of Bayer-Kushida-Brown model.The torsional frequencies and their temperature dependence have been calculated numerically under a two-mode approximation. 0.n comparing the results in 3,5-dichloroanisole with those in 3,5-dichlorophenol it can be seen that they show similar behaviour owing to the absence of hydrogen bonding in both.

Characterization of Actinobacteria Degrading and Tolerating Organic Pollutants

Species of the genera Rhodococcus, Gordonia and Mycobacterium are known as degraders of recalcitrant pollutants. These bacteria are good survivors in harsh environments. Due to such properties these organisms are able to occupy a wide range of environmental niches. The members of these taxa have been suggested as tools for biotechnical applications such as bioremediation and biosynthesis. At the same time several of the species are known as opportunistic human pathogens. Therefore, the detailed characterization of any isolate that has potential for biotechnological applications is very important. This thesis deals with several corynebacterial strains originating from different polluted environments: soil, water-damaged indoor walls, and drinking water distribution systems. A polyphasic taxonomic approach was applied for characterization of the isolates. We found that the strains degrading monoaromatic compounds belonged to Rhodococcus opacus, a species that has not been associated with any health problem. The taxonomic position of strain B293, used for many years in degradation research under different names, was clarified. We assigned it to the species Gordonia polyisoprenivorans. This species is classified under European Biohazard grouping 1, meaning that it is not considered a health hazard for humans. However, there are reports of catheter-associated bacteraemia caused by G. polyisoprenivorans. Our results suggested that the ability of the organism to grow on phthalate esters, used as softeners in medical plastics, may be associated with the colonization of catheters and other devices. In this thesis Mycobacterium lentiflavum, a new emerging opportunistic human pathogen, was isolated from biofilms growing in public drinking water distribution systems. Our report on isolation of M. lentiflavum from water supplies is the second report on this species from drinking water systems, which may thus constitute a reservoir of M. lentiflavum. Automated riboprinting was evaluated for its applicability in rapidly identifying environmental mycobacteria. The technique was found useful in the characterization of several species of rapidly and slowly growing environmental mycobacteria. The second aspect of this thesis refers to characterization of the degradation and tolerance power of several R. opacus, M. murale and G. polyisoprenivorans strains. R. opacus GM-14 utilizes a wide range of aromatic substrates, including benzene, 15 different halobenzenes, 18 phenols and 7 benzoates. This study revealed the high tolerance of R. opacus strains toward toxic hydrophobic compounds. R. opacus GM-14 grew in mineral medium to which benzene or monochlorobenzene was added in amounts of 13 or 3 g l-1, respectively. R. opacus GM-29 utilized toluene and benzene for growth. Strain GM-29 grew in mineral medium with 7 g l-1 of liquid toluene or benzene as the sole carbon source, corresponding to aqueous concentrations of 470 and 650 mg l-1, respectively. Most organic solvents, such as toluene and benzene, due to their high level of hydrophobicity, pass through the bacterial membrane, causing its disintegration. In this thesis the mechanisms of adaptation of rhodococci to toxic hydrophobic compounds were investigated. The rhodococcal strains increased the level of saturation of their cellular fatty acids in response to challenge with phenol, chlorophenol, benzene, chlorobenzene or toluene. The results indicated that increase in the saturation level of cellular fatty acids, particularly that in tuberculostearic acid, is part of the adaptation mechanism of strains GM-14 and GM-29 to the presence of toxic hydrophobic compounds.

Inhibition of the biosynthesis of sterols by phenyl and phenolic compounds in rat liver

The presence of mitochondria increased the incorporation of [2-14C]mevalonate into sterols in a cell-free system from rat liver. Various phenyl and phenolic compounds inhibited the incorporation of mevalonate when added in vitro. p-Hydroxycinnamate, a metabolite of tyrosine, was the most powerful inhibitor among the compounds tested. Catechol, resorcinol and quinol were inhibitory at high concentrations. Organic acids lacking an aromatic ring were not inhibitory. Two hypocholesterolaemic drugs, Clofibrate (α-p-chlorophenoxyisobutyrate) and Clofenapate [α,4-(p-chlorophenyl)phenoxyisobutyrate], which are known to affect some step before the formation of mevalonate in the biosynthesis of cholesterol in vivo, showed inhibition at a step beyond the formation of mevalonate in vitro. The presence of the aromatic ring and the carboxyl group in a molecule appears to be necessary for the inhibition.

Antioxidative long chain alkylresorcinols. Synthesis and deuterium labelling of bioactive compounds present in whole grains

The first synthesis of long chain 5-n-alkylresorcinols (C15-C25) in whole grains and whole grain products by a novel modification of Wittig reaction is described. 5-n-Alkylresorcinols are phenolic lipids that have various effects on biological systems, such as antioxidant activity and interaction with biological membranes. These compounds are considered as biomarkers of whole grain intake, which is connected with reduced risk of cardiovascular diseases and certain cancers. Novel hapten derivatives of 5-n-alkylresorcinols, potential compounds for immunoanalytical techniques, are prepared by the same procedure utilizing microwave catalysed aqueous Wittig reaction as the key step. The synthesised analogues are required by various analytical, metabolism and bioactivity investigations. Four alternative strategies for producing deuterium polylabelled 5-n-alkylresorcinols are explored. Ring-labelled D3-alkylresorcinols were synthesized by acidic H/D exchange. Side chain -labelled D4-derivative was prepared by a total synthesis approach utilizing D2 deuterogenation of a D2-alkene derivative, and deuterogenation of alkynes was investigated in another total synthesis approach. An -D3-labelled alkylresorcinol is isotopically pure and completely stable under all relevant conditions encountered during analytical work. The labelling of another phenolic component of whole grains was explored. The preparation of D3-ferulic acid and related compounds by way of selective methylation of the precursors is described. The deuterated compounds are useful as standards in the quantification of these natural products in various substances, such as food and human fluids. The pure 5-n-alkylresorcinol analogues prepared were used in in vitro experiments on alkylresorcinol antioxidant activity and antigenotoxicity. The in vitro experiments show that alkylresorcinols act as antioxidants, especially when incorporated into biological systems, but possess lower activity in chemical tests (FRAP and DPPH assay). Whole grain alkylresorcinols are shown for the first time to have a protective effect against copper induced oxidation of LDL, and H2O2 or genotoxic faecal water induced damage on HT29 cells.

Odour, dust and non-methane volatile organic-compound emissions from tunnel-ventilated layer-chicken sheds: a case study of two farms

An observational study was undertaken to measure odour and dust (PM10 and PM2.5) emission rates and identify non-methane volatile organic compounds (NMVOCs) and odorants in the exhaust air from two tunnel-ventilated layer-chicken sheds that were configured with multi-tiered cages and manure belts. The study sites were located in south-eastern Queensland and the West Gippsland region of Victoria, Australia. Samples were collected in summer and winter on sequential days across the manure-belt cleaning cycle. Odour emissions ranged from 58 to 512 ou/s per 1000 birds (0.03-0.27 ou/s.kg) and dust emission rates ranged 0.014-0.184 mg/s per 1000 birds for PM10 and 0.001-0.190 mg/s per 1000 birds for PM2.5. Twenty NMVOCs were identified, including three that were also identified as odorants using thermal desorption-gas chromatography-mass spectrometry/olfactometry analysis. Odour emission rates were observed to vary with the amount of manure accumulation on the manure belts, being lowest 2-4 days after removing manure. Odour emission rates were also observed to vary with diurnal and seasonal changes in ventilation rate. Dust emissions were observed to increase with ventilation rate but not with manure accumulation. Some NMVOCs were identified at both farms and in different seasons whereas others were observed only at one farm or in one season, indicating that odorant composition was influenced by farm-specific practices and season.

Ionic Liquids and Microwaves in Promotion of Organic Synthesis : Friedel-Crafts reaction, deuterolabelling and O-Demethylation

The use of ionic liquids in chemical research has gained considerable interest and activity in recent years. Due to their unique and varied physicochemical properties, in comparison to molecular solvents, the potential applications for ionic liquids are enormous. The use of microwave irradiation, as a powerful dielectric heating technique, in synthetic organic chemistry has been known since 1986. Since then, it has gained significant recognition for its research and application in both academia and industry. The use of either ionic liquids or microwave irradiation in synthetic organic chemistry has been known to afford improved, alternative or complimentary selectivities, in comparison to traditional processes. In this study, the use of ionic liquids as solvents, co-solvents and catalytic media was explored in Friedel-Crafts, deuterolabelling and O-demethylation reactions. Alternative methods for the production of a variety of aromatic ketones using the Friedel-Crafts acylation methodology were investigated using ionic liquid catalyst or ionic liquid acidic additive systems. The disclosed methods, i.e. metal bistriflamides and chloroindate ionic liquids systems, possessed good catalytic activity in the synthesis of typical benzophenones. These catalytic systems were also recyclable. Microwave irradiation was found to be useful in the synthesis of various polyhydroxydeoxybenzoins and arylpropanones as synthetic precursors to naturally occurring or potentially bioactive compounds. Under optimized condition, the reaction occurred in only four minutes using systems such as [bmim][NTf2]/HNTf2 and [bmim][BF4]/BF3·OEt2. Naturally occurring polyphenols, such as isoflavones, can possess various types of biological or pharmacological activity. In particular, some are noted for their beneficial effects on human health. Isotopically labelled analogues of polyphenols are valuable as analytical standards in the quantification of these compounds from biological matrices. A new strategy for deuterolabelling of polyphenols was developed using ionic liquids as co-solvents and 35% DCl/D2O, as a cheap deuterium source, under microwave irradiation. Under these conditions, perdeuterated compounds were achieved in short reaction times, in high isotopic purity and in excellent yields. An O-demethylation reaction was developed, using an ionic liquid reaction medium with BBr3 for the deprotection of a variety methyl protected polyphenolic compounds, such as isoflavons and lignans. This deprotection procedure was found to be very practical as the reaction occurred under mild reaction conditions and in short reaction times. The isolation and purification steps were particularly straightforward and high yielding, in comparison to traditional methods.

Homogeneous hydrogenations ofα, β-unsaturated compounds using pentacyanocobaltate (II) anion as catalyst system

Hydrogenation of someα, β-unsaturated carbonyl compounds using potassium pentacyanocobaltate (II), K3Co(CN)5, as a homogeneous catalyst has been investigated. Thus, hydrogenation of 1-carvone (I), mesityl oxide (4), 2-cyclohexenone (8) and benzalacetone (6) afforded the corresponding dihydrocompounds. Hydrogenation ofβ-ionone (10) afforded a mixture of theα, β-dihydrocompounds (14) and (15). In all these cases, it was observed that the reaction proceeded to completion only in the presence of added base. Hydrogenation of 5α-androst-l-en-17β-ol-3-one acetate (19) afforded the saturated compound, 5α-androst-17β-ol-3-one (20) in 60% yield. It was found that other steroid enones and dienones were not reduced by this catalyst system.

A Remarkably Simple One-Step Procedure for the Preparation of alpha-Bromo-alpha,beta-Unsaturated Carbonyl Compounds

An easy and convenient one-step procedure for the conversion of alpha,beta-unsaturated carbonyl compounds into their corresponding bromo-enones using NBS-Et3N center dot 3HBr in the presence of potassium carbonate in dichloromethane at 0 degrees C to room temperature under very mild conditions in high yields and significantly shorter times, is reported.

Melting of an Anchored Bilayer: Phase Transitions in the Organic-Inorganic Hybrid Pervoskite (CH3NH3)(CH3(CH2)(n)NH3)(2)Pb2I7 (n=11, 13, 15, 17)

The conformation, organization, and phase transitions of alkyl chains in organic-inorganic hybrids based on the double pervoskite-slab lead iodides, (CH3NH3)(CH3(CH2)(n)NH3)(2)Pb2I7 (n = 11, 13, 15, 17) have been investigated by X-ray diffraction, calorimetry, and infrared vibrational spectroscopy. In these hybrid solids, double pervoskite (CH3NH3)Pb2I7 slabs are interleaved with alkyl ammonium chains with the anchored alkyl chains arranged as tilted bilayers and adopting a planar all-trans conformation at room temperature. The (CH3NH3)(CH3(CH2)(n)NH3)(2)Pb2I7 compounds exhibit a single reversible phase transition above room temperature with the associated enthalpy change varying linearly with alkyl chain length. This transition corresponds to the melting in two-dimensions of the alkyl chains of the anchored bilayer and is characterized by increased conformational disorder of the methylene units of the chain and loss of tilt angle coherence leading to an increase in the interslab spacing. By monitoring features in the infrared spectra that are characteristic of the global conformation of the alkyl chains, a quantitative relation between conformational disorder and melting of the anchored bilayer is established. It is found that, irrespective of the alkyl chain length, melting occurs when at least 60% of the chains in the anchored bilayer of (CH3NH3)(CH3(CH2)(n)NH3)(2)Pb2I7 have one or more gauche defects. This concentration is determined by the underlying lattice to which the alkyl chains are anchored.

Dimethyl sulfide and other biogenic volatile organic compound emissions from branching coral and reef seawater: Potential sources of secondary aerosol over the Great Barrier Reef

Volatile organic compounds (VOCs) in the headspace of bubble chambers containing branches of live coral in filtered reef seawater were analysed using gas chromatography with mass spectrometry (GC-MS). When the coral released mucus it was a source of dimethyl sulfide (DMS) and isoprene; however, these VOCs were not emitted to the chamber headspace from mucus-free coral. This finding, which suggests that coral is an intermittent source of DMS and isoprene, was supported by the observation of occasional large pulses of atmospheric DMS (DMSa) over Heron Island reef on the southern Great Barrier Reef (GBR), Australia, in the austral winter. The highest DMSa pulse (320 ppt) was three orders of magnitude less than the DMS mixing ratio (460 ppb) measured in the headspace of a dynamically purged bubble chamber containing a mucus-coated branch of Acropora aspera indicating that coral reefs can be strong point sources of DMSa. Static headspace GC-MS analysis of coral fragments identified mainly DMS and seven other minor reduced sulfur compounds including dimethyl disulfide, methyl mercaptan, and carbon disulfide, while coral reef seawater was an indicated source of methylene chloride, acetone, and methyl ethyl ketone. The VOCs emitted by coral and reef seawater are capable of producing new atmospheric particles < 15 nm diameter as observed at Heron Island reef. DMS and isoprene are known to play a role in low-level cloud formation, so aerosol precursors such as these could influence regional climate through a sea surface temperature regulation mechanism hypothesized to operate over the GBR.