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ORGANIC chemistry and PETROLEUM

CHEMISTRY education in universities & colleges and ORGANIC chemistry

Discusses a modern approach to teaching organic chemistry. Organic chemistry courses must begin with structure. Suggests using nuclear magnetic resonance spectroscopy to introduce structure; Introduce students to symmetry axes and planes; Review valence of hydrogen and first-row elements; Give them the equation for calculating the number of sites of unsaturation from the molecular formula; Give students the results of 13C{1H} DEPT with details later; More.

POLYMER research and MASS spectrometry

Examines proposed partial least squares (PLS) multivariate statistical models for predicting concentration of hydrocarbon- and oxygen-containing functional groups for a calibration set of model homopolymers. Plasma-deposited films; Static secondary ion mass spectrometry (SIMS); PLS modeling; Preprocessing; Prediction of surface oxygen and hydrogen concentration.

SEDIMENTATION & deposition research, OCEAN bottom, and CARBONATE minerals

Discusses the mechanism underlying the relative deposition rates of organic carbon and calcite to the sea floor. Effect of total calcite concentration on the specific depth at which calcite dissolves; Control of atmospheric carbon dioxide by ocean carbonate chemistry; Organic carbon degradation in the sediments.

GUMS & resins, ALLERGIES, COLOPHONS, GLYCERYL ethers, PATIENTS, and NUCLEAR magnetic resonance

In the esterification of rosin with glycerol, the main compound formed, glyceryl triabietate, shows low allergenic activity. In this study, compounds formed in smaller amounts, when abietic add (main component in rosin) was esterified with glycerol, were identified as glyceryl-1-monoabietate (GMA), glyceryl-1,2-diabietate (GDA,1,2) and glycery-1,3-diabietate (GDA1,3), using nuclear magnetic resonance (NMR), infra-red (IR) and mass spectrometry (MS) analyses. According to animal experiments, OMA was a contact allergen. No cross-reactivity was seen to allergens in unmodified rosin. Some patients allergic to unmodified rosin reacted when tested with GMA. No reactions were seen to the 2 diabietates. Some patients also reacted to commercial glycerol-modified rosins. OMA together with unmodified abietic acid were identified in these rosin samples. The reactions seen in rosin-sensitive patients to commercial glycerol-esterified rosins probably derive from the unmodified material still present in the product, but could also be the result of OMA obtained from the glycerol derivatization. [ABSTRACT FROM AUTHOR]

RING formation (Chemistry) and TRANSITION metals

Reviews the theoretical and mechanical metal-assisted cycloaddition transition reactions in organic chemistry. Organic and organometallic reactions; Schematically simulated reactions; Metal-assisted transition.

INSECT sex attractants, GRACILLARIIDAE, TORTRICIDAE, YPONOMEUTIDAE, OECOPHORIDAE, PYRALIDAE, GELECHIIDAE, and ALCOHOLS (Chemical class)

Field screening tests of 21 saturated and monounsaturated straight chain C12 and C14 alcohols and their acetates as well as some binary mixtures in dosages of 1 and 0.2 mg/dispenser were carried out in Lithuanian in 1993 and 1994. New sex attractants were determined for males of five moth species of the family Gracillariidae ( E10-12:OH for Phyllonorycter sorbi, E10-12Ac for Ph. cydoniella and Ph. oxyacanthae, Z10-12:OAc for Ph. junoniella, and a mixture of Z10-14:OAc with E9-14:OAc in a 1:10 for Ph. sylvella), for four species of the family Tortricidae ( E10-14:OAc for Endothenia ericetana, Z10-14:OAc in a 10:1 mixture with E11-14:OAc for Eudemis pozphyrana, E11-14:OAc in a 10:1 mixture with E11-14:OH for Dichrorampha petiverella and Cochylis dubitana), for two species of Gelechiidae ( Z9-14:OAc in a mixture with either Z10-14:OAc in a ratio 1:1, E9-14:OAc in a ratio 1:10 or E10-14:OAc in a ratio 10:1 for Bryotropha galhanella, Z10-14:OAc and E9-14:OAc in a ratio 10:1 for B. mundella), as well as for one species of each of the families Yponomeutidae ( Z7-14:OAc for Paraswammerdamia lutarea) and Oecophoridae ( Z10-14:OAc and E9-14:OAc in a ratio 10:1 for Pseudatemelia josephinae). Preliminary composition of sex attractants was established for three moth species of the family Gracillariidae ( Z10-14:OAc in a 1:10 mixture with E9-14:OAc for Phyllonorycter heegerella, Ph. coryli and Ph. dubitella) and for one species of the family Gelechiidae ( Z9-14:OAc for Bryotropha terella). Inhibitors of the sex attractants were found for four leafminer species of the family Gracillariidae ( Z7-, Z9- and Z10-12:OAc for Phyllonorycter sorbi, Z10-, E10-12:OH and E10-14:OH for Ph. mespilella, E10-12:OH for Ph. cydoniella, Z10-12:OH and E10-14:OH for Ph. oxyacanthae), for three species of Tortricidae ( E9-, Z11- and E11-14:OAc for Endothenia ericetana, E11-14:OAc for Gypsonoma minutana, E10- and E11-14:OAc for Epagoge grotiana), and for one species from the family Pyralidae ( Z10-, E10- and E11-14:OAc for Pyrausta aurata). Data from male behaviour tests in tube olfactometers are presented for Phyllonorycter blancardella, Ph. sorbi, Ph. dubitella and Ph. strigulatella and active compounds revealed. [ABSTRACT FROM AUTHOR]

LEAFMINERS, INSECT sex attractants, and PHEROMONES

Dodecyl acetate (12:OAc) (E)-10-dodecenyl acetate (E10-12:OAc) and (E)-10-dodecenol (E10-12:OH) in the ratio 8 : 80 : 12 were collected by solid phase micro-extraction of the volatiles emitted by virgin signalling females of the spotted tentiform leafminer moth, Phyllonorycter blancardella. The same compounds in the ratio 8 : 79 : 13 were extracted from the sex pheromone glands of virgin signalling females of the same species. The chemical structures of the compounds were identified by gas chromatography and mass spectrometry. Trapping results obtained from field tests using synthetic components of the sex pheromone demonstrated that only one component, E10–12:OAc, was essential for the attraction of conspecific males and should be considered as a sex pheromone. [ABSTRACT FROM AUTHOR]

THERMAL analysis, THERMODYNAMICS, INORGANIC chemistry, ORGANIC compounds, and POLYMERS

Summarizes developments and applications in thermal analysis that appeared in Chemical Abstracts from October 1997 to October 1999. Instrumentation; Thermodynamic measurements; Kinetic considerations; Inorganic chemistry; Organic and polymeric materials; Biochemical and natural products; Pharmaceutical applications; Minerals.

OLFACTORY nerve, TOBACCO, MOTH flies, SMELL, CHROMATOGRAPHIC analysis, and ELECTROPHYSIOLOGY

An important question in olfaction is for which odorants receptor neurones have evolved. In the present study, olfactory receptor neurones on the antennae of the tobacco budworm moth Heliothis virescens were screened for sensitivity to naturally occurring plant-produced volatiles by the use of gas chromatography linked to electrophysiology. Volatiles of host as well as non-host plants collected by headspace techniques were used for stimulating the neurones, sequentially via two columns, one polar and one nonpolar installed in parallel in the gas chromatograph. Three types of neurones presented in this paper responded to one, two or three compounds for which the retention times were determined in both column types. The chemical structures of the active components were determined on the basis of mass spectrometry linked to gas chromatography, indicating E-β-ocimene and β-myrcene as stimulants for neurone type 1, E,E-α-farnesene for neurone type 2 and homo-farnesene for neurone type 3. Re-testing authentic materials verified the identifications for the type 1 neurones. The results demonstrate a high specificity for the three types of neurones by strong responses to one or two structurally similar compounds out of hundreds present in a large variety of plants. The study exemplifies plant odour detection by narrowly tuned receptor neurones in a polyphagous moth species. [ABSTRACT FROM AUTHOR]

CETACEA, ENANTIOSELECTIVE catalysis, POLYCHLORINATED biphenyls, and TOXICOLOGY

Isomer-specific concentrations of 41 polychlorinated biphenyls (PCBs) and the enantiomeric ratios (ER) of nine chiral PCBs were determined in the liver of four cetacean species--Risso's dolphin (Grampus griseus), bottlenose dolphin (Tursiops truncatus), fin whale (Balaenoptera physalus), and long-finned pilot whale (Globicephala melaena)--found dead in the Mediterranean Sea. The total PCB concentration (sum of 41 congeners) ranged from 484 to 63,200 ng/g wet weight. The 2,3,7,8 tetrachlorodibenzo- p-dioxin (TCDD) toxic equivalents (TEQs), as defined by the World Health Organization (WHO), ranged from 4.3 to 1,454 pg/g wet weight. The contribution of mono-ortho PCBs was consistently higher than non-ortho PCB congeners, in whale species, whereas in dolphins this predominance was not so clear. The PCB profiles were dominated by congeners 138, 153, and 180 in almost all the investigated samples. Comparison of PCB profiles by using principal component analysis allowed to separate the species into different groups. Polychlorinated biphenyls 170 and 180 seem to be eliminated by the two whale species, and PCB 180 also seems to be eliminated by Risso's dolphins. The PCBs 95, 132, 149, and 176 revealed an enantiomeric excess of the second eluted enantiomer in almost all the cetaceans investigated, where 136 and 174 were racemic or almost racemic. It is the first time that an enantiomeric excess of PCB 84 and 91 has been reported in biological samples. Although it was only possible to calculate them in two dolphin liver samples, the high values of enantiomeric excess found are surprising (86.3 and 32% for PCB 91 and 84, respectively). [ABSTRACT FROM AUTHOR]

ACYLATION, QUINOLINE, AMINES, and HYDROGEN bonding

A significant acceleration of acyl transfer has been achieved on 8-acetoxy-2-oxazolinylquinoline in the presence of benzylamine. Comparison of the aminolysis by the new acylating reagent with that of 8-acetoxyquinoline and 8-acetoxyquinoline-2-carbonitrile has been carried out. The results of these experiments suggest that the proximity of a supplementary basic atom to the ester group increases the participation effect of the basic site mainly by formation of a possible second hydrogen bond. The association constant of benzylamine into the basic cavity of 8-methoxy-2-oxazolinylquinoline (Ka=80 M−1) has been measured by 1H NMR titration experiments. [Copyright &y& Elsevier]

PRINTING, MOLECULAR self-assembly, and MONOMOLECULAR films

A technique for generating a general screening platform consisting of dots of immobilized beads on silicon has been developed via self-sorting and -assembly of different kinds of beads. The dots are defined by a teflon-like film, which due to its hydrophobic characteristics also prevents cross-contamination of liquid from different dots. To enable functionalization of individual dots with different target molecules simultaneously a new way of microcontact printing has been explored where different target solutions are printed in parallel using one stamp. In order to show that this platform can be designed for both biochemical assays and organic chemistry, streptavidin-, amino- and hydroxy-functionalized beads have been self-sorted and -assembled both on separate and common platforms. The self-sorting and -arrangement are based on surface chemistry only, which has not previously been reported. Beads of different sizes and material have successfully been immobilized in line patterns as narrow as 5 μm. Besides silicon, quartz and polyethylene have also been used as substrates. [Copyright &y& Elsevier]

STEREOCHEMISTRY and ENANTIOSELECTIVE catalysis

For the description of the stereoselectivity of (bio)catalytic asymmetric reactions which may proceed via different regio- or stereo-isomeric pathways (e.g. catalysed by epoxide hydrolases, dehalogenases, sulfatases or glycosidases), a parameter ‘RI’ (Retention–Inversion ratio) was introduced in analogy to the Enantiomeric Ratio (E), which describes enantioselectivity. A computer program was developed for the treatment of the kinetics of such single-step processes, which offer the potential of deracemization, i.e. a single stereoisomeric product is formed from a racemate in an enantioconvergent fashion. By analysis of experimentally determined progress curves of the enantiomeric excess of substrate and product (e.e.S, e.e.P, respectively) and the conversion (c), relative first-order rate constants ki, the enantioselectivity (E) and the RI ratio (RI) can be determined; in addition, processes can be simulated based on assumed ki values. [Copyright &y& Elsevier]

NATURAL products, HYDROLYSIS, and EPOXY compounds

A short chemoenzymatic route to two natural products—the first, a constituent of Jamaican rum and the second the (+)-antipode of the gibberelin synergist (−)-Pestalotin—was accomplished based on an enzyme-triggered cascade-reaction. Thus, a racemic halomethyl oxirane was hydrolyzed by bacterial epoxide hydrolases to furnish the corresponding vic-halomethyl-diol, which underwent spontaneous ring-closure to furnish an epoxy alcohol in up to 93% e.e. and ≥99 d.e. Due to the fact that this process was enantioconvergent, the occurrence of the undesired enantiomer was entirely avoided. [Copyright &y& Elsevier]

ESTRONE, CHLOROFLUOROCARBONS, and IRRADIATION

A rapid and efficient deuteration procedure was developed for estrone. Irradiation of estrone in CF3COOD in a microwave oven gave [2,4,16,16-2H4]-estrone in 95% yield. Ultrasound and CF3COOD reflux deuterations of estrone were also studied. [Copyright &y& Elsevier]

COMBINATORIAL chemistry, SOLID-phase analysis, and MICROWAVE heating

Recent advances in microwave-assisted combinatorial chemistry include high-speed solid-phase and polymer-supported organic synthesis, rapid parallel synthesis of compound libraries, and library generation by automated sequential microwave irradiation. In addition, new instrumentation for high-throughput microwave-assisted synthesis continues to be developed at a steady pace. The impressive speed combined with the unmatched control over reaction parameters justifies the growing interest in this application of microwave heating. [ABSTRACT FROM AUTHOR]

GERMACRENE, OVIPARITY, TOBACCO budworm, BUD-moth, OLFACTORY receptors, NEURONS, and ANTENNAE (Biology)

The sesquiterpene germacrene D (GD) activates a major type of olfactory receptor neuron on the antennae of the heliothine moths. In Heliothis virescens females, 80% of the recordings have shown activity of one neuron type responding with high sensitivity and selectivity to GD. With the aim of determining the behavioural significance of this sesquiterpene, we have used a two-choice wind-tunnel to study the preference of mated H. virescens females for host plants with and without (-)-GD added. Tobacco plants containing dispensers with low release rate of (-)-GD had a greater attractiveness than tobacco plants without this substance. In addition, a significant increase of oviposition was found on the plants with (-)-GD. [ABSTRACT FROM AUTHOR]

ESTERS, ENANTIOSELECTIVE catalysis, and ENANTIOMERS

Enantioselective biohydrolysis of sec-alkyl sulfate esters using a bacterial alkylsulfatase from Rhodococcus ruber DSM 44541 proceeded in a stereoselective fashion though inversion of configuration. Thus, from racemic substrates, the corresponding (R)-enantiomers were hydrolyzed selectively to furnish the corresponding sec-alcohol and non-reacted sulfate ester, both of (S)-configuration, which represents a homochiral product mixture. The enantioselectivities were found to depend on the substrate structure and were optimal for sec-sulfate esters in the ω-1 position (up to E=21). Since the enzyme was inactive on prim-sulfate esters, it can be classified as a sec-alkylsulfatase [EC 3.1.6.X]. [Copyright &y& Elsevier]

ESTERS, HYDROLYSIS, and ENANTIOMERS

The Enantioselectivity of the biohydrolysis of sec-alkyl sulfate esters using a bacterial alkylsulfatase from Rhodococcus ruber DSM 44541 was dramatically enhanced in presence of additives (‘enhancers’) such as carbohydrates, polyethylene glycol, detergents, metal ions and through enzyme immobilization. In presence of iron, the E value for the kinetic resolution of (±)-3- and (±)-4-octyl sulfate was improved from E=3.9 to ≥200 and E=1.1 to 10, respectively. [Copyright &y& Elsevier]