Synthesis and properties of aromatic polyesters and brominated polyesters derived from α,α′-bis(4-hydroxyphenyl)-1,4(or 1,3)-diisopropylbenzene

The interfacial polycondensation technique was used for the preparation of polyarylates and brominated polyarylates. Polyarylates and brominated polyarylates were prepared by mixing a solution of diacid chloride such as terephthaloyl chloride, isophthaloyl chloride, or their mixture in dichloromethane with an aqueous alkaline solution of ,-bis(4-hydroxyphenyl)-1,4(or 1,3)-diisopropylbenzene or ,-bis(4-hydroxy-3,5-dibromophenyl)-1,4(or 1,3)-diisopropylbenzene using triethylbenzylammonium chloride as the phase transfer agent. Moderate to high molecular weight polyarylates with _inh up to 1.27 dL/g were obtained, and most of them could be cast into tough and flexible films depending on the polymer composition. In general, polymers containing more 1,3-isomer or isophthaloyl chloride moieties gave transparent and flexible films and had lower glass transition temperatures and higher solubility. Although these polymers have two isopropylidene linkages in their repeating units, they still exhibit moderately high thermal stability and show no obvious weight loss before 400 °C. The introduction of bromine on the polymer backbone caused a decrease of inherent viscosity, crystallinity, and thermal stability of the polyarylates, while causing an increase in glass transition temperature and a great enhancement of fire retardancy.     

Alkylation of α-Methylnaphthalene with Long-Chain Olefins over Large-Pore Zeolites

The liquid-phase alkylation of -methylnaphthalene with long-chain olefins (C_11–12) has been investigated firstly in the presence of H-Y and H-Beta zeolites with different pore architectures. The H-Y zeolites exhibited outstanding catalytic performances. The influences of various reaction parameters like temperature, pressure, mole ratio of -methylnaphthalene to olefins (n _rea), solvent concentration, volume hour space velocity (VHSV) and time on stream on the reaction were studied in detail. Under the optimal reaction parameters, more than 90% conversion of olefins and 100% selectivity for the desired mono-alkyl methylnaphthalene were achieved.     

Suppression of the α → β-nickel hydroxide transformation in concentrated alkali: Role of dissolved cations

The presence of dissolved cations such as Al and Zn in alkaline electrolyte (6 M KOH) suppresses the -nickel hydroxide transformation. The uptake of Al (10 mol%) and Zn (30 mol%) exhibited by the active material likely stabilizes the -phase. Dissolved Al is deleterious to the performance of the nickel hydroxide electrode, whereas, dissolved Zn enhances the specific discharge capacity of nickel hydroxide by approximately 25% showing that the mode of metal uptake is different in the two cases.     

Asymmetric structure analysis of active surface-sites by in situ polarized total-reflection fluorescence EXAFS

An in situ polarization-dependent total reflection fluorescence yield EXAFS system has been developed to analyze the asymmetric structures of catalytically active metal sites on single crystal surfaces. This technique separately reveals the bonding feature parallel and perpendicular to the support surface. The systems of Cu ion on -quartz(0001), Co oxide on -alumina(0001), and Pt₄ on -alumina(0001) were investigated as model surfaces of supported catalytic systems. The location of Cu sites on -quartz(0001), the epitaxial growth mode of Co₃O₄ on -alumina(0001), and the Pt raft structure with metal-support interaction in Pt₄ / -alumina(0001) were observed.     

Stereospecific antennal response by red turpentine beetle,Dendroctonus valens to chiral monoterpenes from ponderosa pine resin

The antennal response ofDendroctonus valens to host monoterpenes from the resin of ponderosa pine was studied using the electroantennogram (EAG) technique. Male and female beetles were given a single dose of each of 11 different monoterpenes. Response amplitude to the different compounds did not vary between sexes and was generally well correlated with results from field attraction studies. Response to (S)-(–)--pinene was greatest. The relative amplitude of the responses to the (R)-(+) and (S)-(–) enantiomers of a-pinene, however, were reversed from their relative attractiveness in the field. A dose-response study was conducted for the (R)-(+) and (S) -(–) enantiomers of a-pinene, plus a reciprocal differential saturation test with successive doses of first one enantiomer of-pinene and then the other. Comparison of EAG traces suggests different receptors for the two stereoisomers of-pinene. Differential saturation curves suggest that while one set of receptors may respond to both enantiomers, some receptors respond only to the (S)-(–) enantiomer.     

Selective synthesis of α-olefins on Fe-Zn Fischer-Tropsch catalysts

Fe/Zn oxides promoted with K and Cu selectively produce -olefins at typical Fischer-Tropsch synthesis conditions (2/1 H₂/CO, 1 MPa, and 270°C). The simultaneous presence of K and Cu introduces a synergistic activity enhancement while maintaining the high olefin selectivity obtained by alkali promotion. Structural and morphological differences in Fe-Zn oxides prepared from ammonium glycolate complexes or precipitated from nitrate solutions have only a small influence on catalytic properties. Catalyst behavior is strongly influenced by synergistic promoter effects (Cu, K) and by the controlled in situ conversion of iron oxide precursors to carbides.     

Additional male mediterranean fruitfly (Ceratitis capitata wied.) Attractants from Angelica seed oil (Angelica archangelica L.)

Two sesquiterpene hydrocarbons, -copaene and -ylangene, were isolated from bioactive fractions of angelica seed oil and were shown by field bioassays to be attractive to the male Mediterranean fruit fly. Their relative attractiveness, compared with the(+)-and (–)--copaene enantiomers, are: (+)--copaene>angelica -copaene>angelica -ylangene>(–)--copaene. The enantiomer ratios for the two compounds are: -copaene, 61.4% (+), 38.6% (–); -ylangene, 91.9% (+), 8.1% (–).trans--Bergamotene was also isolated from the same fractions, but in sufficient quantity for bioassay [enantiomer ratio: 95.7% (+), 4.3% (–)].     

Highly Efficient Platinum-Catalyzed Enantioselective Hydrogenation of Trifluoroacetoacetates in Acidic Solvents

The hydrogenation of methyl-, ethyl- and isopropyl-4,4,4-trifluoroacetoacetates to the corresponding chiral trifluoromethyl alcohols has been investigated over Pt/A1₂O₃ modified by O-methyl-cinchonidine. Up to 96% ee and 1850 h^-1 average TOF have been achieved in the synthesis of this important chiral building block. The special role of reaction medium and particularly the impact of water and acids on enantiodiscrimination are discussed.     

Silyl Triflate-Initiated Ring-Opening Polymerizations of Cyclosiloxanes

Polymer yields between 70 and 85% form in ring-opening polymerizations of trimeric cyclosiloxanes initiated with trimethylsilyl triflate in the presence of a selective scavenger for protic acids, 2,6-di-t-butylpyridine. Examples include the polymerization of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane (F₃) and hexamethylcyclotrisiloxane (D₃). Siloxane bond redistribution is essentially absent and data are presented establishing a nonterminating polymerization giving an average of roughly one trimethylsilyl group per chain. The present observations contrast with other work that suggests that the presence of free triflic acid is required for initiation with trimethylsilyl triflate.     

Highly stereoselective epoxidation of (−)-α-pinene over chiral transition metal (salen) complexes occluded in zeolitic hosts

Various transition metal complexes of seven different salen ligands have been incorporated in specially modified zeolitic host materials. The thus immobilized sterically demanding complexes have been tested in the diastereoselective epoxidation of (–)--pinene in the liquid phase in an autoclave at room temperature and elevated pressure using O₂ as oxidant. In most cases conversions of 100% could be achieved. Best results so far – 100% conversion, 96% epoxide chemoselectivity and 91% diastereomeric excess – have been obtained in the presence of the entrapped [(R,R)-(N,N)-bis(3,5-di-tert-butylsalicylidene)-1,2-diphenylethylenediamino]cobalt(II) = Co(salen-5) complex. Computer simulations were done in order to prove that the reaction can take place inside the pore system, i.e., (–)--pinene is able to diffuse through the microporous entrances of the carrier material.     

A study of the influence of the synthesis conditions upon the catalytic properties of silicoaluminophosphate molecular sieves

The skeletal isomerization of 1butene was performed over a series of silicoaluminophosphate molecular sieves with AEL structure (SAPO11). The results were compared with those obtained over an aluminophosphate molecular sieve (AlPO₄11). The three SAPO11 samples, with different acidic properties, were synthesized by either varying the chemical composition of the synthesis gel or by varying the preparation time of the aforementioned gel. The catalytic results indicate that irrespective of how the acidity of the SAPO11 samples is changed (viz., independently of the method elected to modify the acidic properties of the samples), a close parallelism between the selectivity towards the skeletal isomerization and the number of (moderate + strong) Brønsted acid sites (sites retaining pyridine above 623 K) was observed for the SAPO11 solids. These results, definitively, indicate the participation of these acid sites in the skeletal isomerization process.     

Residual effects of growing mungbean and uridbean on the yield and nitrogen uptake of a succeeding wheat crop

A two year field experiment was carried out at the Indian Agricutural Research Institute, New Delhi - 110012, India to assess the effect of mungbean (Vigna radiata L.) and uridbean (Vigna mungo L.) residues on the yield and N uptake of a succeeding wheat crop as compared to sorghum fodder. Sorghum produced 3.5–7.5 times more dry matter and removed 2–3 times more nitrogen than mungbean or uridbean during same duration (80 ± 10 days) of their growth. Without N application the grain yield of wheat following mungbean and uridbean (without residue incorporation) was 0.45 and 0.48 t ha^–1 more than the yield of wheat following sorghum fodder. These yields were equivalent to that predicted when 36 and 38 kg urea-N ha^–1, respectively, was directly applied to wheat. The residual effects of these grain legumes were higher when succeeding wheat was fertilized with 60 kg urea-N ha^–1; at this level mungbean and uridbean spared 52 and 43 kg urea-N ha^–1, respectively, in succeeding wheat. The residual effect of mungbean and uridbean further increased when their residue was incorporated in soil; with this practice they spared 94 and 115 kg urea-N ha^–1, respectively, without N application to wheat and 74 and 82 kg urea-N ha^–1, respectively, with an application of 60 kg urea-N ha^–1 to wheat.Mungbean and uridbean, without residue incorporation, increased aboveground plant-N uptake of succeeding wheat by 11.5–34.9 and 10.8–34.0 kg N ha^–1, respectively; whereas with residue incorporation, they increased aboveground plant-N content of succeeding wheat by 26.1–45.8 and 32.7–47.7 kg N ha^–1, respectively.The results of the present study indicate that there is both an indirect sparing effect and a direct residual effect of mungbean and uridbean on the nitrogen needs of succeeding wheat, more so when their residues are incorporated in soil.     

Electrosynthesis of 4,4′-dinitroazobenzene on PbO2 electrodes

Parameters which affect the electrosynthesis of 4,4-dinitroazobenzene from p-nitroaniline on platinum and PbO₂ electrodes were investigated and optimum conditions were determined. Maximum conversion efficiency for electrosynthesis was 95% with a pure -PbO₂ electrode. It was found that the electrocatalytic activity of a PbO₂ electrode depends upon its / ratio and its degree of crystallinity. The effects of the added base and water on the conversion efficiency were also elucidated.     

Enantioselective hydrogenation of α-ketoesters over Pt/alumina modified with cinchonidine: theoretical investigation of the substrate-modifier interaction

Enantio-differentiation in the asymmetric hydrogenation of -ketoesters to -hydroxyesters over platinum catalysts modified with cinchona-alkaloid modifiers occurs through interaction of the ketoester with the cinchona modifier. The structure of the probable transition complex has been calculated for the system methyl pyruvate (substrate) cinchonidine (modifier) using molecular mechanics and quantum chemistry techniques at both ab initio and semiempirical levels. The calculations suggest that protonated cinchonidine is energetically more likely to interact with the substrate and that the crucial interaction occurs via hydrogen bonding of the quinuclidine nitrogen and the oxygen of the -carbonyl moiety of methyl pyruvate. In this complex the methyl pyruvate is transformed into a half-hydrogenated species which is adsorbed on the platinum surface and on hydrogenation yields the product methyll actate. Theoretical studies indicate that adsorption of the complex leading to (R) -methyl lactate is energetically more favourable than that of the corresponding complex which yields (S) -methyl lactate, which may be the key for the enantio-differentiation.     

Hydroformylation of functional alkenes with heterodonor phosphine rhodium catalysts: substrate or ligand directed regioselectivity?

The catalytic activity and selectivity of heterodonor phosphine rhodium catalysts prepared in situ were tested in the hydroformylation of functional alkenes (ethyl acrylate, methyl methacrylate, styrene, 4-vinyl-1-cyclohexene, dicyclopentadiene and cis-1,2,3,6-tetrahydrophthalic anhydride). Systematic variation of the heterodonor atom in the ortho position of the ligand showed that the heterodonor atom has a significant influence on the activities and selectivities of the reaction. However, the activity seems to depend mainly on the modifying ligand, and the regioselectivity mainly on the substrate (i.e., the structure and functionality of the alkene). Nevertheless, regioselective control is only obtained through synergy between the substrate and the catalyst. Clear regiocontrol was observed in the hydroformylation of ,-unsaturated esters and styrene with an in situ formed o-(thiomethylphenyl)diphenylphosphine rhodium catalyst.     

Multichemical defense of plant bugHotea gambiae (westwood) (Heteroptera: Scutelleridae)

Chemical defense in larvae of the plant bugHotea gambiae has been investigated. Results of analyses (GC, GC-MS) on the secretions from the three dorsally situated larval abdominal defense (scent) glands are reported. The secretion from the first abdominal gland consists of a mixture of C₁₀ and C₁₅ isoprenoids: (C₁₀) -pinene, -pinene, limonene, -phellandrene; (C₁₅) -caryophyllene, caryophyllene oxide, -humulene, and (the major component) humulene epoxide II. The secretions from the second and third abdominal glands are similar mixtures consisting of (E)-2-decenal, (E)-4-oxohex-2-enal, andn-tridecane together with lesser amounts of (E)-2-hexenal,n-dodecane, and other materials. Isoprenoid defense is now known from four species of plant bugs (Heteroptera) associated with Malvaceae.     

Apple Fruit Infested with Codling Moth are More Attractive to Neonate Codling Moth Larvae and Possess Increased Amounts of (E,E)-α-Farnesene

Apple fruit artificially infested with codling moth larvae attracted significantly more neonate larvae of the codling moth, Cydia pomonella than uninfested fruit. A greater number of larvae responded to odor in an olfactometer from codling moth-infested cold-stored Red Delicious thinning apples than uninfested apples. Immature Granny Smith, Red Delicious, or Golden Delicious apples that were infested on the tree for five days by codling moth larvae were more attractive to neonate codling moth larvae than similar but uninfested fruit of the same varieties. Apples infested on the tree and sampled five days later also contained significantly greater amounts of the larval attractant (E,E)--farnesene, compared to uninfested apples. Other types of injury to apple fruit did not produce results similar to that from codling moth infestation, either in increased attractiveness to codling moth larvae or in increased quantities of (E,E)--farnesene. These results are consistent with the reported attractiveness of (E,E)--farnesene to neonate codling moth larvae.     

Enhancement of the activities with feedstream doping by tetrachloromethane in the oxidative dehydrogenation of propane on α-magnesium pyrovanadate

The oxidative dehydrogenation of propane to propylene has been investigated on -magnesium pyrovanadate (Mg₂V₂O₇) at 723 K in the presence and absence of tetrachloromethane (TCM). Under the present conditions, the conversion of propane and the selectivity to propylene were 5.0 and 74.5%, respectively, in the absence of TCM while those were 14.0 and 70.2%, respectively, upon addition of a small amount of TCM (P(TCM) = 0.34 kPa) into the feedstream on the catalyst. The conversion of propane on Mg₂V₂O₇ without oxidant in the presence and absence of TCM revealed that a contribution of lattice oxygen in the catalyst to the oxidation was strongly controlled by the addition of TCM, resulting in the enhancement of the activity with TCM.     

Response of the European elm bark beetle,Scolytus multistriatus (Coleoptera: Scolytidae), to isomers and components of its pheromone

Laboratory bioassays (two methods) and field tests demonstrated synergistic action of the three components [(–)-4-methyl-3-heptanol (I); (–)-2,4-dimethyl-5-ethyl-6,8-dioxabicylo[3.2.1]octane (-multistriatin) (II); and (–)--cubebene (III)] of the pheromone bouquet ofScolytus multistriatus. Individually and in pairs the components were slightly attractive; I+II was clearly the most active doublet. Indirect evidence indicates that only one of the four enantiomers of I is active. Of the , , and isomers of II, only the is active. With the addition of compound I, slightly attractive extract from mated females became nearly as active as extract from virgin females.     

Synergistic interaction between potato glycoalkaloidsα-solanine andα-chaconine in relation to destabilization of cell membranes: Ecological implications

In studies of the lysis of rabbit erythrocytes, red beet cells, andPenicillium notatum protoplasts by the potato glycoalkaloids -solanine and -chaconine, the latter was consistently the more membrane-disruptive compound and erythrocytes the more susceptible cell type. A 11 mixture of solanine and chaconine produced pronounced synergistic effects in all three test systems. In beet cells, such effects were apparent from an early stage of treatment and persisted over a period of several hours. With erythrocytes and fungal protoplasts, the synergism was maximal with mixtures containing approximately 70% chaconine, whereas with beet cells it peaked at approximately 40% chaconine. Synergistic interactions between solanine and chaconine also occurred with regard to cholesterol binding in vitro, with a maximum response corresponding to the 50% mixture. The implications of these findings for the nature and efficacy of chemical defense systems in plants are discussed.