The acetal concept : regioselective access toortho,ortho-diphenols via dibenzo-1,3-dioxepines

Traditional methods are ill-suited for the synthesis of ortho,ortho-biphenols, a structural motif found in many polyphenolic natural products, as well as synthetically useful compounds such as the chiral ligands binol, vapol, and vanol. The new route consists of a radical-based reaction of an acetal-tethered biphenyl ether substrate and subsequent hydrolytic cleavage of the dibenzo-1,3-dioxepine intermediate.

ortho-Bromo(propa-1,2-dien-1-yl)arenes : substrates for domino reactions

o-Bromo(propa-1,2-dien-1-yl)arenes exhibit novel and orthogonal reactivity under Pd catalysis in the presence of secondary amines to form enamines (concerted Pd insertion, intramolecular carbopalladation, and terminative Buchwald–Hartwig coupling) and of amides to form indoles (addition, Buchwald–Hartwig cyclization, and loss of the acetyl group). The substrates for these reactions can be accessed in a reliable and highly selective two-step process from 2-bromoaryl bromides.

The loss of CO from the ortho, meta and para forms of deprotonated methyl benzoate in the gas phase

The ortho, meta and para anions of methyl benzoate may be made in the source of a mass spectrometer by the S(N)2(Si) reactions between HO- and methyl (o-, m-, and p-trimethylsilyl)benzoate respectively. All three anions lose CO upon collisional activation to form the ortho anion of anisole in the ratio ortho>>meta > para. The rearrangement process is charge directed through the ortho anion. Theoretical calculations at the B3LYP/6-311++G(d,p)//HF/6-31+G(d) level of theory indicate that the conversion of the meta and para anions to the ortho anion prior to loss of CO involve 1,2-H transfer(s), rather than carbon scrambling of the methoxycarbonylphenyl anion. There are two mechanisms which can account for this rearrangement, viz. (A) cyclisation of the ortho anion centre to the carbonyl group of the ester to give a cyclic carbonyl system in which the incipient methoxide anion substitutes at one of the two equivalent ring carbons of the three membered ring to yield an intermediate which loses CO to give the ortho anion of anisole, and (B) an elimination reaction to give an intermediate benzyne-methoxycarbonyl anion complex in which the MeOCO- species acts as a MeO- donor, which then adds to benzyne to yield the ortho anion of anisole. Calculations at the B3LYP/6-311++G(d,p)//HF/6-31+G(d) level of theory indicate that (i) the barrier in the first step (the rate determining step) of process A is 87 kJ mol(-1) less than that for the synchronous benzyne process B, and (ii) there are more low frequency vibrations in the transition state for benzyne process B than for the corresponding transition state for process A. Stepwise process A has the lower barrier for the rate determining step, and the lower Arrhenius factor: we cannot differentiate between these two mechanisms on available evidence.

Pyroxene thermometry of rhyolite lavas of the Bruneau–Jarbidge eruptive center, Central Snake River Plain

The Bruneau–Jarbidge eruptive center of the central Snake River Plain in southern Idaho, USA produced multiple rhyolite lava flows with volumes of <10 km³ to 200 km³ each from ~11.2 to 8.1 Ma, most of which follow its climactic phase of large-volume explosive volcanism, represented by the Cougar Point Tuff, from 12.7 to 10.5 Ma. These lavas represent the waning stages of silicic volcanism at a major eruptive center of the Yellowstone hotspot track. Here we provide pyroxene compositions and thermometry results from several lavas that demonstrate that the demise of the silicic volcanic system was characterized by sustained, high pre-eruptive magma temperatures (mostly ≥950 °C) prior to the onset of exclusively basaltic volcanism at the eruptive center. Pyroxenes display a variety of textures in single samples, including solitary euhedral crystals as well as glomerocrysts, crystal clots and annealed microgranular inclusions of pyroxene ±magnetite± plagioclase. Pigeonite and augite crystals are unzoned, and there are no detectable differences in major and minor element compositions according to textural variety — mineral compositions in the microgranular inclusions and crystal clots are identical to those of phenocrysts in the host lavas. In contrast to members of the preceding Cougar Point Tuff that host polymodal glass and mineral populations, pyroxene compositions in each of the lavas are characterized by single rather than multiple discrete compositional modes. Collectively, the lavas reproduce and extend the range of Fe–Mg pyroxene compositional modes observed in the Cougar Point Tuff to more Mg-rich varieties. The compositionally homogeneous populations of pyroxene in each of the lavas, as well as the lack of core-to-rim zonation in individual crystals suggest that individual eruptions each were fed by compositionally homogeneous magma reservoirs, and similarities with the Cougar Point Tuff suggest consanguinity of such reservoirs to those that supplied the polymodal Cougar Point Tuff. Pyroxene thermometry results obtained using QUILF equilibria yield pre-eruptive magma temperatures of 905 to 980 °C, and individual modes consistently record higher Ca content and higher temperatures than pyroxenes with equivalent Fe–Mg ratios in the preceding Cougar Point Tuff. As is the case with the Cougar Point Tuff, evidence for up-temperature zonation within single crystals that would be consistent with recycling of sub- or near-solidus material from antecedent magma reservoirs by rapid reheating is extremely rare. Also, the absence of intra-crystal zonation, particularly at crystal rims, is not easily reconciled with cannibalization of caldera fill that subsided into pre-eruptive reservoirs. The textural, compositional and thermometric results rather are consistent with minor re-equilibration to higher temperatures of the unerupted crystalline residue from the explosive phase of volcanism, or perhaps with newly generated magmas from source materials very similar to those for the Cougar Point Tuff. Collectively, the data suggest that most of the pyroxene compositional diversity that is represented by the tuffs and lavas was produced early in the history of the eruptive center and that compositions across this range were preserved or duplicated through much of its lifetime. Mineral compositions and thermometry of the multiple lavas suggest that unerupted magmas residual to the explosive phase of volcanism may have been stored at sustained, high temperatures subsequent to the explosive phase of volcanism. If so, such persistent high temperatures and large eruptive magma volumes likewise require an abundant and persistent supply of basalt magmas to the lower and/or mid-crust, consistent with the tectonic setting of a continental hotspot.

Ortho-Dihydroxyl-9,10-anthraquinone dyes as visible-light sensitizers that exhibit a high turnover number for hydrogen evolution

Pt/TiO2 sensitized by the cheap and organic ortho-dihydroxyl-9,10-anthraquinone dyes, such as Alizarin and Alizarin Red, achieved a TON of approximately 10 000 (TOF > 250 h−1 for the first ten hours) during >80 hours of visible light irradiation (>420 nm) for photocatalytic hydrogen evolution when triethanolamine was used as the sacrificial donor. The stability and activity enhancements can be attributed to the two highly serviceable redox reactions involving the 9,10-dicarbonyl and ortho-dihydroxyl groups of the anthracene ring, respectively

Developing spatial infrastructures for the Q.U.T. Samford Ecological Research Facility.

Staff and students of the Surveying and Spatial Sciences discipline at QUT have worked collaboratively with the Institute of Sustainable Resources in the creation and development of spatial information layers and infrastructure to support multi-disciplinary research efforts at the Samford Ecological Research Facility (SERF). The SERF property is unique in that it provides staff and students with a semi-rural controlled research base for multiple users. This paper aims to describe the development of a number of spatial information layers and network of survey monuments that assist and support research infrastructure at SERF. A brief historical background about the facility is presented along with descriptions of the surveying and mapping activities undertaken. These broad ranging activities include introducing monument infrastructure and a geodetic control network; surveying activities for aerial photography ground-control targets including precise levelling with barcode instruments; development of an ortho-rectified image spatial information layer; Real-Time-Kinematic Global Positioning Systems (RTK-GPS) surveying for constructing 100metre confluence points/monuments to support science-based disciplines to undertake environmental research transects and long-term ecological sampling; and real-world learning initiative to assist with water engineering projects and student experiential learning. The spatial information layers and physical infrastructure have been adopted by two specific yet diverse user groups with an interest in the long-term research focus of SERF.

Three-dimensional hydrogen-bonded structures in the guanidinium salts of the monocyclic dicarboxylic acids rac-trans-cyclohexane-1,2-dicarboxylic acid (2:1, anhydrous), isophthalic acid (1:1, monohydrate) and terephthalic acid (2:1, trihydrate).

The structures of bis(guanidinium)rac-trans-cyclohexane-1,2-dicarboxylate, 2(CH6N3+) C8H10O4- (I), guanidinium 3-carboxybenzoate monohydrate CH6N3+ C8H5O4- . H2O (II) and bis(guanidinium) benzene-1,4-dicarboxylate trihydrate, 2(CH6N3+) C8H4O4^2- . 3H2O (III) have been determined and the hydrogen bonding in each examined. All three compounds form three-dimensional hydrogen-bonded framework structures. In anhydrous (I), both guanidinium cations give classic cyclic R2/2(8) N--H...O,O'(carboxyl) and asymmetric cyclic R1/2(6) hydrogen-bonding interactions while one cation gives an unusual enlarged cyclic interaction with O acceptors of separate ortho-related carboxyl groups [graph set R2/2(11)]. Cations and anions also associate across inversion centres giving cyclic R2/4(8) motifs. In the 1:1 guanidinium salt (II), the cation gives two separate cyclic R1/2(6) interactions, one with a carboxyl O-acceptor, the other with the water molecule of solvation. The structure is unusual in that both carboxyl groups give short inter-anion O...H...O contacts, one across a crystallographic inversion centre [2.483(2)\%A], the other about a two-fold axis of rotation [2.462(2)\%A] with a half-occupancy hydrogen delocalized on the symmetry element in each. The water molecule links the cation--anion ribbon structures into a three-dimensional framework. In (III), the repeating molecular unit comprises a benzene-1,4-dicarboxylate dianion which lies across a crystallographic inversion centre, two guanidinium cations and two water molecules of solvation (each set related by two-fold rotational symmetry), and a single water molecule which lies on a two-fold axis. Each guanidinium cation gives three types of cyclic interactions with the dianions: one R^1^~2~(6), the others R2/3(8) and R3/3(10) (both of these involving the water molecules), giving a three-dimensional structure through bridges down the b cell direction. The water molecule at the general site also forms an unusual cyclic R2/2(4) homodimeric association across an inversion centre [O--H...O, 2.875(2)\%A]. The work described here provides further examples of the common cyclic guanidinium cation...carboxylate anion hydrogen-bonding associations as well as featuring other less common cyclic motifs.

Prediction model of the buildup of volatile organic compounds on urban roads

A model to predict the buildup of mainly traffic-generated volatile organic compounds or VOCs (toluene, ethylbenzene, ortho-xylene, meta-xylene, and para-xylene) on urban road surfaces is presented. The model required three traffic parameters, namely average daily traffic (ADT), volume to capacity ratio (V/C), and surface texture depth (STD), and two chemical parameters, namely total suspended solid (TSS) and total organic carbon (TOC), as predictor variables. Principal component analysis and two phase factor analysis were performed to characterize the model calibration parameters. Traffic congestion was found to be the underlying cause of traffic-related VOC buildup on urban roads. The model calibration was optimized using orthogonal experimental design. Partial least squares regression was used for model prediction. It was found that a better optimized orthogonal design could be achieved by including the latent factors of the data matrix into the design. The model performed fairly accurately for three different land uses as well as five different particle size fractions. The relative prediction errors were 10–40% for the different size fractions and 28–40% for the different land uses while the coefficients of variation of the predicted intersite VOC concentrations were in the range of 25–45% for the different size fractions. Considering the sizes of the data matrices, these coefficients of variation were within the acceptable interlaboratory range for analytes at ppb concentration levels.

Thermal stability of the ‘cave’ mineral brushite CaHPO4•2H2O -mechanism of formation and decomposition

Thermogravimetry combined with evolved gas mass spectrometry has been used to ascertain the stability of the ‘cave’ mineral brushite. X-ray diffraction shows that brushite from the Jenolan Caves is very pure. Thermogravimetric analysis coupled with ion current mass spectrometry shows a mass loss at 111°C due to loss of water of hydration. A further decomposition step occurs at 190°C with the conversion of hydrogen phosphate to a mixture of calcium ortho-phosphate and calcium pyrophosphate. TG-DTG shows the mineral is not stable above 111°C. A mechanism for the formation of brushite on calcite surfaces is proposed, and this mechanism has relevance to the formation of brushite in urinary tracts.

Effects of climate change on the wash-off of volatile organic compounds from urban roads

The predicted changes in rainfall characteristics due to climate change could adversely affect stormwater quality in highly urbanised coastal areas throughout the world. This in turn will exert a significant influence on the discharge of pollutants to estuarine and marine waters. Hence, an in-depth analysis of the effects of such changes on the wash-off of volatile organic compounds (VOCs) from urban roads in the Gold Coast region in Australia was undertaken. The rainfall characteristics were simulated using a rainfall simulator. Principal Component Analysis (PCA) and Multicriteria Decision tools such as PROMETHEE and GAIA were employed to understand the VOC wash-off under climate change. It was found that low, low to moderate and high rain events due to climate change will affect the wash-off of toluene, ethylbenzene, meta-xylene, para-xylene and ortho-xylene from urban roads in Gold Coast. Total organic carbon (TOC) was identified as predominant carrier of toluene, meta-xylene and para-xylene in <1µm to 150µm fractions and for ethylbenzene in 150µm to >300µm fractions under such dominant rain events due to climate change. However, ortho-xylene did not show such affinity towards either TOC or TSS (total suspended solids) under the simulated climatic conditions.

Single crystal raman spectroscopy of natural finnemanite and comparison with the synthesised analogue

The single crystal Raman spectra of natural mineral finnemanite Pb5(AsO3)3Cl from the Långban locality, Filipstad district, Värmland province, Sweden are presented for the first time. It is a hexagonal mineral belonging to the ortho arsenite group, where the [AsO3]3- ion is isolated. The spectra of finnemanite are characterized by a strong band at 734 cm-1 overlying a shoulder at 726 cm-1, and broad overlapping bands in the lower wavenumber with the strongest band positioned at 174 cm-1. Band assignments were made based on band symmetry, experimental band positions from literature and DFT calculated Raman spectrum, and spectral comparison with other ortho arsenite minerals reinerite, cafarsite, and nealite and synthetic lead arsenite compounds Pb2(AsO2)3Cl, Pb2As2O5, and PbAs2O4 . The band at 734 cm-1 was assigned to υ1(AsO3), bands at 726 and 640 cm-1 assigned to υ3, 372 and 357 cm-1 to υ2, and 244, 239 and 207 cm-1 to υ4. The single crystal spectra of finnemanite showed good mode separation, allowing bands to be assigned a symmetry species of Ag, E1g, or E2g.

Water–rock interactions : an investigation of the relationships between mineralogy and groundwater composition and flow in a subtropical basalt aquifer

A holistic study of the composition of the basalt groundwaters of the Atherton Tablelands region in Queensland, Australia was undertaken to elucidate possible mechanisms for the evolution of these very low salinity, silica- and bicarbonate-rich groundwaters. It is proposed that aluminosilicate mineral weathering is the major contributing process to the overall composition of the basalt groundwaters. The groundwaters approach equilibrium with respect to the primary minerals with increasing pH and are mostly in equilibrium with the major secondary minerals (kaolinite and smectite), and other secondary phases such as goethite, hematite, and gibbsite, which are common accessory minerals in the Atherton basalts. The mineralogy of the basalt rocks, which has been examined using X-ray diffraction and whole rock geochemistry methods, supports the proposed model for the hydrogeochemical evolution of these groundwaters: precipitation + CO 2 (atmospheric + soil) + pyroxene + feldspars + olivine yields H 4SiO 4, HCO 3 -, Mg 2+, Na +, Ca 2+ + kaolinite and smectite clays + amorphous or crystalline silica + accessory minerals (hematite, goethite, gibbsite, carbonates, zeolites, and pyrite). The variations in the mineralogical content of these basalts also provide insights into the controls on groundwater storage and movement in this aquifer system. The fresh and weathered vesicular basalts are considered to be important in terms of zones of groundwater occurrence, while the fractures in the massive basalt are important pathways for groundwater movement.

Infrared spectra of Mg-SiO smokes : comparison with analytical electron microscopy studies

An important component of current models for interstellar and circumstellar evolution is the infrared (IR)spectral data collected from stellar outflows around oxygen-rich stars and from the general interstellar medium [1]. IR spectra from these celestial bodies are usually interpreted as showing the general properties of sub-micron sized silicate grains [2]. Two major features at 10 and 20 microns are reasonably attributed to amorphous olivine or pyroxene (e.g. Mg2Si04 or MgSi03) on the basis of comparisons with natural standards and vapor condensed silicates [3-6]. In an attempt to define crystallisation rates for spectrally amorphous condensates, Nuth and Donn [5] annealed experimentally produced amorphous magnesium silicate smokes at 1000K. On analysing these smokes at various annealing times, Nuth and Donn [5] showed that changes in crystallinity measured by bulk X-ray diffraction occured at longer annealing times (days) than changes measured by IR spectra (a few hours). To better define the onset of crystallinity in these magnesium silicates, we have examined each annealed product using a JEOL 1OOCX analytical electron microscope (AEM). In addition, the development of chemical diversity with annealing has been monitored using energy dispersive spectroscopy of individual grains from areas <20nm in diameter. Furthermore, the crystallisation kinetics of these smokes under ambient, room temperature conditions have been examined using bulk and fourier transform infrared (FTIR)spectra.

Analytical electron microscopy of Mg-SiO smokes; a comparison with infrared and XRD studies

Experimentally obtained Mg.SiO smokes were studied by analytical electron microscopy using the same samples that had been previously characterized by repeated infrared spectroscopy. Analytical electron microscopy shows that unannealed smokes contain some degree of microcrystallinity which increases with increased annealing for up to 30 hr. An SiO2 polymorph (tridymite) and MgO may form contemporaneously as a result of growth of forsterite (Mg2SiO4) microcrystallites in the initially nonstoichiometric smokes. After 4 hr annealing, forsterite and tridymite react to enstatite (MgSiO3). We suggest that infrared spectroscopy and X-ray diffraction analysis should be complemented by detailed analytical electron microscopy to detect budding crystallinity in vapor phase condensates.

Electron petrography of fine-grained matrix in the Karoonda C4 carbonaceous chondrite

The study of matrices of rare Type 4 carbonaceous chondrites can reveal important information on parent body rnetamorp~ic processes and provide a comparison with processes on parent bodies of ordinary chc-idrites. Reflectance spectra (Tholen, 1984) from the two largest asteroids in the asteroid belt, Ceres and Pallas, suggest that they may be metamorphosed carbonaceous chondrites. These two asteroids constitute - onethird of the mass in the asteroid belt implying that type 4-6 carbonaceous chondrites are poorly represented in the meteorite collection and may be of considerable importance. The matrix of the C4 chondrite Karoonda has been investigated using a JEOL 2000FX analytical electron microscope (AEM) with an attached Tracor-Northem TN5500 energy dispersive spectrometer (EDS). In previous studies (Scott and Taylor, 1985; Fitzgerald, 1979; Van Schmus, 1969), the petrography of the Karoonda matrix has been described as consisting largely of coarse-grained (50-200 urn in size) olivine and plagioclase (20-100 um in size), associated with micrometer sized magnetite and rare sulphides. AEM observations on matrix show that in addition to these large grains, there is a significant fraction (10 vol%) of interstitial fine grained phases « 5 urn). The mineralogy of these fine-grained phases differs in some respects from that of the coarser-grained matrix identified by optical and SEM techniques (Scott and Taylor, 1985; Fitzgerald, 1979; Van Schmus, 1969). I~ particular crystals of two compositionally distinct pyroxenes « 2 urn in size) have been identified which have not been previously observed in Karoonda by other analytical techniques. Thin film microanalyses (Mackinnon et al., 1986) of these two pyroxenes indicate compositions consistent with augite and low-Ca pyroxene (- Fs27). Fine-grained anhedral olivine « 2 urn size) is the most abundant phase with composition -Fa29' This composition is essentially indistinguishable from that determined for coarser-grained matrix olivines using an electron microprobe (Scott and Taylor, 1985; Fitzgerald, 1979; Van Schmus, 1969). All olivines are associated with subhedral magnetites « 1 urn size) which contain significant Cr (- 2%) and Al (- 1%) as was also noted for larger sized Karoonda magnetites by Delaney et al. (1985). It has recently been suggested (Burgess et al., 1987) on the basis of sulphur release profiles for S-isotope analyses of Karoonda that CaS04 (anhydrite) may be present. However, no sulphate phase has, as yet, been identified in the matrix of Karoonda. Low magnification contrast images suggest that Karoonda may have a significant porosity within the fine-grained matrix fraction. Most crystals are anhedral and do not show evidence for significant compaction. Individual grains often show single point contact with other grains which result in abundant intergranular voids. These voids frequently contain epoxy which was used as part of the specimen preparation procedure due to the friable nature of the bulk sample.