Abstract  Secondary organic aerosols have been characterized by evolved gas analysis (EGA). Hydrocarbons selected as aerosol precursors were representative of anthropogenic emissions (cyclohexene, cyclopentene, 1-decene and 1-dodecene, n-dodecane, 0-zylene, and 1,3,3-tn-metbylbenzene) and of biogenic emissions (the terpenes "alpha"-pinene, "beta"-pinene and "delta"-limonene and the sesquiterpene trans-caryophyllene). Also analyzed by EGA were samples of secondary, primary (highway tunnel), and ambient (urban) aerosols before and after exposure to ozone and other photochemical oxidants. The major features of the EGA thermograms (amount of CO2 evolved as a function of temperature) are described. The usefulness and limitations of EGA data for source apportionment of atmospheric particulate carbon are briefly discussed.

Abstract  Formylation of aromatic compounds such as toluene, xylene, mesitylene, and halogenatedbenzene was carried out in HSO3F-SbF5 under atmospheric CO pressure at 0 degrees C. In HSO3F-SbF5, both formylation and sulfonylation took place to give formyl and sulfonyl compounds depending on the acidity of the solution. Diformylation of polynuclear aromatic compounds such as naphthalene, diphenyl, diphenylmethane and dibenzyl was carried out in HF-SbF5 system by a one-pot reaction.

Abstract  Ozonolysis reactions of alkenes are suggested to play major roles in the chemistry of the troposphere. Rate constants for the gas-phase reactions of O3 with a series of alkenes were determined using relative rate technique based on GC/FID measurements of alkene decays. Experiments were carried out in air over the temperature range of 278-353 K at an atmospheric pressure of 760 Torr. An excess of 1,3,5-trimethylbenzene was used as a HO radical scavenger in all experiments. Arrhenius parameters were calculated for ozonolysis of 1-butene, 1-pentene, 1-hexene, 1-heptene, 2-methyl-1-butene, isobutene, trans-2-butene, trans-2-pentene, cis-2-pentene, trans-2-hexene, cis-2-hexene, 3-chloropropene, 1,1-dichloroethene, and isoprene from temperature-dependent studies of the rate constants. The rate constants obtained in this study are compared with previous literature data. A good linear correlation between the logarithms of the rate constants and calculated HOMO energies of selected alkenes is observed. However, no clear correlation could have been drawn for chlorinated substituted alkenes.

Abstract  Hydroxyl radical yields are reported for the gas-phase ozonolyses of a range of alkenes. 1,3,5-Trimethylbenzene was employed as an OH tracer, and the diminution in its concentration was used to calculate OH yields by both a simple analytical kinetic expression and a numerically integrated model. The following OH yields were obtained, relative to alkene consumed: ethene (0.14), propene (0.32), 2-methylpropene (0.60), 2,3-dimethyl-2-butene (0.89), isoprene (0.44), -pinene (0.24), and -pinene (0.83). A structure activity relationship (SAR) is presented for the estimation of OH yields based on structural moieties and reaction branching ratios. Reaction stoichiometries ([alkene]/[ozone]) are also reported, along with primary carbonyl yields measured in the presence and absence of excess SO2, both under "OH-free" conditions. Reaction stoichiometries are shown to be correlated with alkene OH yields, and the mechanistic implications of this observation are discussed. The fractional increase in primary carbonyl yield in the presence of excess SO2 is shown to be inversely related to the OH yield and is interpreted as a measure of the fraction of the vibrationally excited Criegee intermediate that is stabilized in air at a pressure of 1 atm.

Abstract  Acylation of aromatic compounds (benzene, toluene, p-xylene, mesitylene, anisole, naphthalene, methylnaphthalene and methoxynaphthalene) by an acyl chloride (benzoyl chloride. phenylacety chloride, propionyl chloride or butyryl chloride) in high yield, in a short reaction period (3 h), even in the presence of moisture in the aromatic substrate or solvent (dichloroethane), can be accomplished at low temperature (80+/-1degreesC) using an InCl3 impregnated Si-MCM-41 catalyst in low catalyst concentration. (C) 2002 Elsevier Science Ltd. All rights reserved.

Abstract  As a model protein with quite large dimensions, Bovine Serum Albumin (BSA) has been used to evaluate the influence of the distinct pore structural characteristics of three mesocellular foam (MCF) materials prepared with or without the addition of ammonium fluoride and with varying 1,3,5-trimethylbenzene/Pluronic P123 (TMB/P123) ratios. SBA-15 was also studied for comparative purposes. Characterisation by X-ray diffraction and electron microscopy confirmed the characteristic spheroid cell structure of the MCF pores. Nitrogen adsorption/desorption isotherms at 77 K revealed the different pore structural parameters of the MCF, viz. pore volume (1.8-2.4 cm3/g), cell size (24.6-28.5 nm) and window size (11.3-17.3 nm), as obtained by the NLDFT method. The equilibrium adsorption isotherms and the kinetic adsorption data for BSA at 298 K and pH 5 were well fitted by the Langmuir model and pseudo-second-order kinetic model, respectively. The results showed that adsorption onto the material possessing a window size of 11.3 nm was mostly restricted to the external surface, while a considerable increase in the maximum adsorption capacity from 120 mg/g to 500-600 mg/g was observed when the window size was above the critical dimension of 13.9 nm. In the latter cases, the maximum adsorption capacities could be related to the pore volume rather than to the total surface area. The confined BSA molecules were strongly immobilised in the cells, since only a small proportion was desorbed from the material with windows of 17.3 nm dimensions on contact with a buffer solution of pH 7. [ABSTRACT FROM AUTHOR] Copyright of Adsorption Science & Technology is the property of Multi-Science Publishing Co Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract  H-Pro-Pro-Asp-NH21is a versatile catalyst for asymmetric aldol reactions. Within the catalyst structure, both the N-terminal secondary amine and the carboxylic acid are crucial for efficient catalysis. Here, the importance of the arrangement of these two functional groups towards each other was examined. Several analogues of H-Pro-Pro-Asp-NH2were prepared in which the secondary amine and the carboxylic acid occupy different positions. Evaluation of their catalytic properties revealed that the placement of these two functional groups is highly critical for efficient catalysis. Even seemingly small structural modifications, for example, one methylene group more or less, can modify the catalytic properties significantly. The results demonstrate the difficulty in rationally designing a peptidic catalyst and the value of combinatorial smart screening methods for catalyst discovery. Abbreviations:Fmoc9-fluorenylmethoxycarbonyl; HCTU2-(6-chloro-1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate; MSNT1-(mesitylene-2-sulfonyl)-3-nitro-1H-1,2,4-triazole; TNBS2,4,6-trinitrobenzenesulfonic acid.

Abstract  The shape selectivity properties of USY zeolite crystallites is discussed, and is based on catalyst characterization, molecular simulation, catalytic experiments of model compounds and kinetic modeling. Typical FCC catalysts are prepared with different HY crystallite sizes (0.4 and 0.9 mu m), and are structurally and chemically characterized with nitrogen and argon adsorption/desorption isotherms, temperature-programmed desorption of ammonia and infrared spectroscopy. Catalyst characterization is carried out before and after the hydrothermal treatment (steaming) of the catalyst. Pore-size distribution analysis demonstrates that the effect of the steaming treatment in the Y zeolite results in window enlargement. The influences of structural changes of steam treatment on reactivity is evaluated with the catalytic conversion of 1,2,4-trimethylbenzene in a novel fluidized CREC riser simulator. It is proven that steaming enlarges zeolite windows and influence the 1,2,4-TMB product distribution. A slight modification of the window diameter is proven to significantly affect the adsorbent-adsorbate interactions. Focus is particularly given to the catalyst selectivity toward the tetramethylbenzene isomers, and the "transition-state shape selectivity" is proven to be controlling the product distribution and is consistent with molecular mechanics calculations.

Abstract  The Borexino experiment, aimed at measuring the 7Be solar neutrinos, is currently under construction at the underground National Laboratories of Gran Sasso in central Italy. The Gran Sasso underground labs are located below 1,400 m of rocks. The equivalent shielding for cosmic rays is 3,800 m of water equivalent, and the residual muon flux is ∼1/m2/h. The number of muons crossing the Borexino detector is 10,000/day, to be compared with the number of 7Be neutrino events in the central fiducial detector of ∼10/day. A muon veto sub-detector was designed with the purpose of reducing background from muons and cosmogenic nuclides below 1 event per day in the spectral region of the equivalent energy between 250 and 800 keV, where the signal from the 7Be neutrinos is expected. The muon veto sub-detector consists of two separate parts. Four hundred photomultiplier tubes measure the scintillation photons and the Cerenkov photons produced by muons either in the 300 tons of scintillator or in the 1000 tons of pseudocumene buffer. Two hundred photomultiplier tubes measure the Cerenkov photons produced by muons in the water shield surrounding the pseudocumene buffer. The paper presents an overview of the muon background in Borexino and an estimate of the background reduction which is expected to be produced by the muon veto. A full discussion of the experimental apparatus is provided as well.

Abstract  The advantages of homogeneous and heterogeneous catalytic systems are combined in stationary liquid-phase catalysts such as the system [PtCl2(CH3CN)2] in BF3.H2O on clay or silica supports, which is used here for hydrogenation of arenes. The hydrogenation can be performed under relatively mild conditions, the products are separable by simple filtration, and the hydrogenation proceeds selectively, as shown for a 1:1:1:1 mixture of benzene, toluene, o-xylene, and 1,2,4-trimethylbenzene.

Abstract  Volatile compounds formed by oxidation of rapeseed oil at 60 C in open beakers were studied as a function of time over 289 h. A direct inlet gas-phase FT-IR method was introduced and compounds indicating lipid oxidation were detected and quantified. The development of 1,3,5-trimethylbenzene, 2,4-hexadienal, 2-methyl-1,3-butadiene, 2-methyltetrahydrofuran, acetic acid, methyl cyclopentane, methyl hexanoate, n-butanal, n-hexanal, n-octanal, n-propanal, and trans,trans-2,4-heptadienal was followed. The results showed that gas-phase FT-IR is a potential method of fast analysis for monitoring oil quality. Headspace-gas chromatography-mass spectrometry (HS-GC-MS) was used for compound identification.

Abstract  Tetrafluoro-4-nitropyridine derivatives have been synthesized and separated successfully by HPLC. The resulting fluorinated amines and 4-amino3-chlorotrifluoropyridine have also been diazotized and the resulting diazonium ions coupled to mesitylene giving the corresponding azo-compounds: 2,3,4,6-tetrafluoro-4-(2,4,6-trimethylphenylazo)pyridine (9) (80%), 3-chloro-2,5,6-trifluoro-4-(2,4,6-trimethylphenylazo)pyridine (23) (83%), 2,3,6-trifluoro-4-nitro-5-(2,4,6-trimethylphenylazo)pyridine (20) (80%): 2,3,5-trifluoro-4-nitro-6-(2,4,6-trimethylphenylazo)pyridine (21) (84%). Treatment of these azo-compounds mentioned earlier with sodium methoxide in methanol/tetrahydro furan gave 3,6-difluoro-2-methoxy-4-nitro- 5-(2,4,6-trimethylphenyl azo)pyridine (24) (37%), 3-fluoro-2,5dimethoxy-4-nitro-6-(2,4,6-trimethylphenylazo)pyridine (26) (49%), 2,3-difluoro-4,5-dimethoxy-6-(2,4,6-trimethylphenylazo)pyridine (25) (32%), 3-chloro-2,3,5-trifluoro-6-methoxy-4-(2,4,6-trimethylphenylazo) pyridine 24 (87%), 3-chloro-3,5-difluoro-2,6-dimethoxy4-(2,4,6-trimethylphenylazo)-pyridine 23 (83%). The two diazepines 25 and 26 were successfully separated by HPLC. The thermolysis of the synthesized azocompounds in boiling mestylene gave the corresponding diazepines: 1,2,4-trifluoro-7,9-dimethyl-11-H-pyrido[4,3-c]benzo[1,2]diazepine (15) (75%), -1,4-difluoro-3-methoxy-7,9-dimethyl-11-H-pyrido[4,3-c]benzo[1,21diazepi ne (32) (80%) and 3,4-difluoro-l-methoxy-7,9-dimethyl-11-H-pyrido[4,3-c]benzo[1,2]diazepin e (33) (9%). The structural diazepine-isomers 32 and 33 were also separated by HPLC.

Abstract  C9 arenes consist of a series of isomeric compounds with very close boiling points. Although hard to separate by distillation, e.g. the separation of 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzene, it was possible to perform flow sheet and equipment analyses of the actual operating data by computer simulation and produce a successful flow sheet revamp. That is, with new separation technology and structured packing technology, the original flow sheet was rearranged and columns were reconstructed. The conclusion of the retrofit demonstrated increased throughput, purity and productivity of 1,2,4-trimethylbenzene (the main product). In addition, 1,3,5-trimethylbenzene, a very important by-product, was obtained at higher purity. This reconstruction brings significant economic benefit and advanced technology for the separation and utilization of C9 arenes in worldwide operations. (c) 2007 Curtin University of Technology and John Wiley & Sons, Ltd.

Abstract  The purpose of this study is to develop an emission inventory for major anthropogenic air pollutants and VOC species in the Yangtze River Delta (YRD) region for the year 2007. A "bottom-up" methodology was adopted to compile the inventory based on major emission sources in the sixteen cities of this region. Results show that the emissions of SO2, NOx, CO, PM10, PM2.5, VOCs, and NH3 in the YRD region for the year 2007 are 2391.8 kt, 2292.9 kt, 6697.1 kt, 3115.7 kt, 1510.8 kt, 2767.4 kt, and 458.9 kt, respectively. Ethylene, mp-xylene, o-xylene, toluene, and 1,2,4-trimethylbenzene, 2,4-dimethylpentane, ethyl benzene, propylene, 1-pentene, and isoprene are the key species contributing 77% to the total OFPs. The spatial distribution of the emissions shows the emissions and OFPs are mainly concentrated in the urban and industrial areas along the Yangtze River and around the Hangzhou Bay. The industrial sources including power plant, other fuel combustion facilities, and non-combustion processes contribute about 97%, 86%, 89%, 91%, and 69% of the total SO2, NOx, PM10, PM2.5, and VOC emissions. Vehicles take up 12.3% and 12.4% of the NOx and VOC emissions, respectively. Regarding OFPs, chemical industry, domestic use of paint and printing, and gasoline vehicle contribute 38.2%, 23.9%, and 11.6% to the ozone formation in the YRD region. [ABSTRACT FROM AUTHOR] Copyright of Atmospheric Chemistry & Physics Discussions is the property of Copernicus Gesellschaft mbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract  The reactions of ozone with alkenes are an important source of hydroxyl (OH) radicals; however, quantification of their importance is hindered by uncertainties in the absolute OH yield. Hydroxyl radical yields for the gas-phase ozonolysis of isoprene are determined in this paper by four different methods: (1) The use of cyclohexane as an OH scavenger, and the production of cyclohexanone, (2) The use of 1,3,5-trimethylbenzene as an OH tracer, and the diminution in its concentration, (3) A kinetic method in which the OH yield was obtained by performing a series of pseudo-first-order experiments in the presence or absence of an OH scavenger (cyclohexane), (4) The OH and HO2 yields were determined by fitting the temporal OH and HO2 profiles following direct detection of absolute OH and HO2 concentrations by laser induced fluorescence at low pressure (Fluorescence Assay by Gas Expansion-FAGE). The following OH yields for the ozonolysis of isoprene were obtained, relative to alkene consumed, for each method: (1) Scavenger (0.25 0.04), (2) Tracer (0.25 0.03), (3) Kinetic study (0.27 0.02), and (4) Direct observation (0.26 0.02), the error being one standard deviation. An averaged OH yield of 0.26 0.02 is recommended at room temperature and atmospheric pressure and this result is compared with recent literature determinations. The HO2 yield was directly determined for the first time using FAGE to be 0.26 0.03. [ABSTRACT FROM AUTHOR] Copyright of Atmospheric Chemistry & Physics Discussions is the property of Copernicus Gesellschaft mbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract  Accurate thermal expansion coefficient alpha(p), speed-of-sound and density measurements found in the literature have been used to characterize the general behavior with pressure of the constant pressure heat capacity C(p) of benzene and toluene. The results agree well with direct measurements of C(p) found in the literature. Indirect methods for estimating C(p) at high pressures are discussed. Alpha(p) results obtained with an expansion technique using a differential method have been used to characterize the high-pressure behavior of C(p) for mesitylene.

Abstract  Pulse radiolysis study of liquid benzyl chloride has been carried out at room temperature. In order to identify transient species that absorb in the UV-vis region, various scavengers were used including oxygen, ethanol, pyrrole, biphenyl, and mesitylene (1,3,5-trimethylbenzene). The spectrum of the benzyl cation was obtained by subtracting the transient spectrum of the 0.6 M solutions of ethanol in O-2-saturated benzyl chloride from that for O-2-saturated benzyl chloride. The difference spectrum obtained has a strong absorption band at 303 +/- 2 nm and a weak broad band near 500 nm. The analyses of end products formed in the y radiolysis of benzyl chloride were done in the presence and absence of scavengers. The formation of benzyl ethyl ether with a G value of 0.9 from a 0.6 M solution of ethanol in O-2-saturated benzyl chloride was taken as evidence that added ethanol reacts with benzyl cations to give benzyl ethyl ether. Some pulse radiolysis experiments were performed with benzyl bromide. Transient spectra observed in benzyl bromide are similar to those observed in benzyl chloride. It is, however, inferred from the product analysis that the radiolytic mechanisms of benzyl bromide appreciably differ from those of benzyl chloride.

Abstract  The oxidation of pseudocumene in the benzene nucleus can be effected in HOAc solution by using inorganic oxidizing agents containing oxygen, such as NaNO₃, hetero-polyacids, O₂, Na₂S₂O₈ and H₂O₂, with Pd(OAc)₂ as catalyst. Na₂S₂O₈ and H₂O₂ are the most effective, being also active in the absence of Pd(II).

Abstract  Study of computational model of the concerted Diels-Alder reaction between 9,10-dimethyl anthracene (as donor) and tetracyanoethylene (as acceptor) in absence and in presence of aromatic solvents (benzene, mesitylene and hexamethylbenzene, as donors) using an AM1 semi-empirical method. AM1 method used to study the neutral charge transfer complex models that could be expected between donor and acceptor during the course of the concerted Diels-Alder reaction. Calculated enthalpies of reaction of the charge transfer complexes models showed physical and chemical meaning for explain the effect of aromatic solvents on the kinetic process of concerted Diels-Alder reaction that contains tetracyanoethylene.

Abstract  Mesitylketene was generated flash photolytically in aqueous solution by the photo-Wolff reaction of 2,4,6-trimethyldiazoacetophenone and also by rearrangement of mesitylynol obtained through photodecarbonylation of mesitylhydroxycyclopropenone, and rates of hydration of this ketene were measured in dilute perchloric acid, sodium perchlorate, and sodium hydroxide solutions as well as in concentrated sodium perchlorate and perchloric acid solutions. In dilute solution only an uncatalyzed reaction and a sodium-hydroxide-catalyzed process were observed, both of which could be attributed to nucleophilic attack, by water and by hydroxide ion, respectively, at the ketene carbonyl carbon atom. In concentrated sodium perchlorate solutions, a mild decrease in reaction rate with increasing salt concentration was observed, as expected on the basis of decreasing water activity and a consequent slowing of the uncatalyzed reaction. A similar mild decrease was found in perchloric acid solutions up to but this then gave way to a rate increase that became dominant above This appearance of acid catalysis indicates a change in reaction mechanism from nucleophilic attack of water to an electrophilic process involving rate-determining protonation on the -carbon atom of the ketene group. Analysis of the acid-catalyzed reaction rate by the CoxYates method gives the catalytic coefficient This, when compared with for ketene itself, shows that the mesityl group retards acid-catalyzed hydration by a factor of 2200, and consequently the acid-catalyzed reaction of this, and other aromatic ketenes as well, becomes apparent only under strongly acidic conditions. Keywords: mesitylketene, ketene hydration, acid catalysis, CoxYates excess acidity correlation.On a gnr le msitylctne par photolyse clair en solution aqueuse l'aide d'une raction de photo-Wolff de la 2,4,6-trimthyldiazoactophnone ainsi que par un rarrangement du msitylynol obtenu par photodcarbonylation de la mesitylhydroxycyclopropenone et on a mesur ses vitesse d'hydratation en solution dilue d'acide perchlorique, de perchlorate de sodium et d'hydroxyde de sodium ainsi que dans des solutions concentres de perchlorate de sodium et d'acide perchlorique. En solutions dilues, on n'a observ qu'une raction qui n'est pas catalyse et un processus catalys par l'hydroxyde de sodium; les deux peuvent tre attribus une attaque nuclophile, respectivement par l'eau et l'ion hydroxyde, au niveau du carbone du carbonyle du ctne. En solutions concentres d'acide perchlorique, on a observ une lgre diminution de la vitesse de raction avec une augmentation de la concentration de sel, tel qu'on peut s'y attendre en se basant sur une diminution de l'activit de l'eau accompagnant un ralentissement de la raction qui n'est pas catalyse. On a aussi observ une lgre diminution semblable dans les solutions d'acide perchlorique jusqu' des concentrations de HClO4d'environ 1M; toutefois, au-del de cette valeur, il y a une augmentation de la vitesse qui devient dominante au-dessus de [HClO4]2M. Cette catalyse acide apparente indique qu'il se produit un changement de mcanisme de raction qui passe d'une attaque nuclophile de l'eau un processus lectrophile impliquant une protonation du carbone en du groupe ctne dans l'tape qui dtermine la vitesse. Une analyse de la vitesse de raction acidocatalyse par la mthode de CoxYates fournit un coefficient catalytique Cette valeur, compare celle observe avec le ctne non substitu montre que le groupe msityle retarde la raction d'hydratation acidocatalyse par un facteur de 2200 et que la raction acidocatalyse de ce ctne ainsi que celles d'autres ctnes aromatiques ne deviennent apparentes que dans des conditions fortement acides. Motscls: msitylne, hydratation de ctne, catalyse acide, corrlation d'acidit en excs de CoxYates. [Traduit par la rdaction]

Abstract  The photolysis of dimesitylbis(trimethylsilyl)germane (3) in hexanes or THF, at low temperature, has been investigated as a potential method for the preparative-scale synthesis of tetramesityldigermene (5). A product mixture, consisting of hexamethyldisilane, mesitylene, 2-trimethylsilylmesitylene (7), a new germacyclobutene (8), and an unidentified polymer, was obtained. No evidence for the formation of tetramesityldigermene (5) was observed. (English) [ABSTRACT FROM AUTHOR] On a tudi la photolyse du dimsitylbis(trimthylsilyl)germane (3) dans les hexanes ou le THF, de faibles tempratures, comme mthode potentielle de la synthse l'chelle prparative de ttramsityldigermne (5). On a obtenu un mlange de produits form d'hexamthyldisilane, de msitylne, de 2-trimthylsilylmsitylne (7), d'un nouveau germacyclobutne (8) et d'un polymre non identifi. On n'a observ aucune formation du ttramsityldigermne (5). (French) [ABSTRACT FROM AUTHOR] Copyright of Canadian Journal of Chemistry is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract  The structure of 2-(4-carbomethoxy-2-nitrophenoxy)-1,3,5-trimethylbenzene, C17H17NO5, has been determined by X-ray diffraction. The crystals are monoclinic, a=8.352(4), b=17.892(10), c=10.966(6), =100.59(3) , P21/cwith Z=4. The intensities of 3877 independent reflections were measured on a four circle diffractometer; 2272 of these reflections were used to obtain a final least-squares residual of 0.053 and traditional Rfactor of 0.054. The general conformation is similar to that found earlier for differently substituted diphenyl ethers. Comparison of this structure with those previously determined indicates that distortions in ring angles are primarily a result of electronic rather than steric effects.On a dtermin la structure cristalline du (carbomthoxy-4 nitro-2 phnylate)-2 trimthyl-1,3,5 benzne, C17H17NO5, par diffraction de rayons-X. Les cristaux sont monocliniques, a=8.352(4), b=17.892(10), c=10.966(6), =100.59(3) , P21/cavec Z=4. On a mesur les intensits de 3877 rflexions indpendantes l'aide d'un diffractomtre quatre cercles. On a utilis 2272 de ces rflexions pour affiner la structure jusqu' une valeur de Rpondre de 0.053 et une valeur d Rconventionnelle de 0.054. La conformation gnrale de cette molcule se rapproche de celle observe antrieurement pour des diphnylthers substitus dans diverses positions. Une comparaison de cette structure avec d'autres dtermines antrieurement indique que les distorsions dans les angles du cycle sont dues principalement des effets lec troniques plutt que striques. [Traduit par le journal]

Abstract  H-atom scrambling and cistransisomerization of dideuteroethylene have been observed with various photosensitizers: benzene, toluene, p-xylene, o-xylene, m-xylene, mesitylene, fluorobenzene, and benzotrifluoride. The pressure dependences are satisfactorily explained in terms of the two excited state mechanism previously proposed.Using Kassel's equation for the rate of unimolecular reactions, the energies of the triplet states of the sensitizers have been estimated. The values obtained coincide with the spectroscopic values.non disponible

Abstract  In order to study the effect of association with -donors, the proton resonance signal of chloroform in the aromatic solvents benzene, toluene, mesitylene, chlorobenzene, o-dichlorobenzene, bromobenzene, nitrobenzene and in the olefinic solvents 1-hexene, cyclohexene, and cyclohexadiene was measured as a function of concentration. The observed shifts of the resonance signal are indicative of specific complex formation. In the aromatic solvents benzene, toluene, and mesitylene, complex formation results in an anomalous shift of the chloroform resonance to high field, which can be attributed to a large induced diamagnetism resulting from the circulation of -electrons in the aromatic ring. An approximate calculation indicates that the chloroform molecule in the complex is oriented with the hydrogen atom near the six-fold axis above the plane of the aromatic ring and the chlorines directed away from the ring. In nitrobenzene this type of association with chloroform gives way to n-donor association with the oxygen atom of the nitro group. This type of association also occurs to some extent in the halogenated benzenes. A small shift of the chloroform signal to low field is observed with the olefinic solvents, which is attributable to weak -donor association. Analysis of the freezing-point diagrams of the binary systems with chloroform provide further evidence of complex formation.non disponible

Abstract  Enthalpies of solution (Hs) of 1-octanol and five model compounds (di-n-butyl ether, n-heptyl methyl ether, 1-fluoro-octane, 1-chlorooctane, and n-octane) have been determined in 13 solvents (heptane, cyclohexane, CCl4, 1,1,1-trichloro-ethane, 1,2-dichloroethane, triethylamine, butyl ether, ethyl acetate, DMF, DMSO, benzene, toluene, mesitylene), and combined with heats of vaporization to give enthalpies of transfer from vapor to solvent (H(vS)). These values have been used to calculate the enthalpy of hydrogen bond formation (Hh) of 1-octanol with each solvent, using the pure base (PB), solvation enthalpy (SE), and non-hydrogen-bonding baseline (NHBB) methods. Evidence is presented suggesting that (a) the SE method is susceptible to mismatches of the 1-octanol vs. model polar and dispersion interactions, (b) the PB method is sensitive to polar interaction mismatches, whereas (c) the NHBB method compensates for both polar and dispersion interactions mismatches. The (apparent) Hhvalues determined by the SE and PB methods may be as much as several kcal/mol (nearly 50%) too large, because of the inclusion of other polar and dispersion interactions. The NHBB method is therefore preferred for determining enthalpies of H-bond formation from calorimetric data. However, apparent Hhvalues from the SE and PB methods can be incorporated into total solvatochromic equations using TaftKamiet *, , and parameters, to provide enthalpies of H-bond formation in good agreement with Hh(NHBB).On a dtermin les enthalpies de solution (Hs) de l'octanol-1 et de cinq composs modles (ther di-n-butylique, mthoxy-1 heptane, fluoro-1 octane, chloro-1 octane et n-octane) dans treize solvants organiques (heptane, cyclohexane, CCl4, trichloro-1,1,1 thane, dichloro-1,2 thane, trithylamine, ther butylique, actate d'thyle, DMF, DMSO, benzne, tolune, msitylne) et on a combin ces valeurs avec les chaleurs de vaporisation afin d'obtenir les enthalpies de transfert de la phase vapeur au solvant (H(vS)). On a utilis ces valeurs pour calculer l'enthalpie de formation de la liaison hydrogne (Hh) de l'octanol-1 avec chacun des solvants en utilisant les mthodes de la base pure (BP), de l'enthalpie de solvatation (ES) et de la ligne de base sans liaisons hydrognes (LBSLH). Les donnes obtenues suggrent que: (a) la mthode des ES peut tre affecte si les interactions soit polaires ou de dispersion de l'octanol-1 sont mal assorties par rapport au compos modle, (b) la mthode de la BP est sensible aux mauvais assortiments qui peuvent tre dus aux interactions polaires tandis que (c) la mthode de la SLH permet de compenser aussi bien les mauvais assortiments dus aux interactions polaires que ceux dus aux interactions de dispersion. Les valeurs (apparentes) du Hh, telles que dtermines par les mthodes des ES et de la BP, peuvent tre survalues par plusieurs kcal/mol (presque 50%) cause de l'inclusion d'autres interactions polaires et de dispersion. On prfre donc la mthode de la LBSLH pour dterminer les enthalpies de formation des liaisons hydrognes partir des donns calorimtriques. Cependant, on peut incorporer les valeurs apparentes du Hhobtenues partir des mthodes des ES et de la BP dans les quations solvatochromiques totales en utilisant les paramtres *, et de TaftKamlet pour obtenir des enthalpies de formation de la liaison hydrogne qui sont en bon accord avec les valeurs de Hh(LBSLH). [Traduit par le journal]