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A kinetic study on [S.sub.N]Ar reactions of 1-aryloxy-2,4-dinitrobenzenes (1a-1h) with a series of cyclic secondary amines in 80 mol% water - 20 mol% DMSO at 25.0 [+ or -] 0.1 [degrees]C is reported. The plots of [k.sub.obsd] versus amine concentration curve upward except for the reactions of substrates possessing a strong electron-withdrawing group in the leaving aryloxide with strongly basic piperidine. The curved plots indicate that the reactions proceed through both uncatalytic and catalytic routes. Linear Bronsted-type plots have been obtained for the uncatalyzed and catalyzed reactions of 1-(4-nitrophenoxy)-2,4-dinitrobenzene (1a) with [[beta].sub.nuc] = 0.84 and 0.78, respectively. The Yukawa-Tsuno plot for the uncatalyzed reactions of 1a-1h with piperidine results in an excellent linear correlation with [rho] = 1.66 and r = 0.31. In contrast, rate constants for catalyzed reactions are independent of the electronic nature of the substituent in the leaving group. The current [S.sub.N]Ar reactions have been proposed to proceed via a zwitterionic intermediate (MC[+ or -]) that partitions to products through uncatalytic and catalytic routes. The catalyzed reaction from MC[+ or -] has been concluded to proceed through a concerted mechanism with a six-membered cyclic transition state ([TS.sub.cycl]) rather than via a stepwise pathway with a discrete anionic intermediate ([MC.sup.-]), the traditionally accepted mechanism. Medium effects on the reactivity and reaction mechanism are discussed. Particularly, hydrogen bonding of the amines to water precludes formation of kinetically significant dimers found in some aprotic solvents; no explicit role for water in the catalytic transition state is required or proposed. The specific stabilization of the leaving aryloxides substituted with strong electron-withdrawing groups accounts for the lack of the catalytic pathway in these systems (1a-1c) with piperidine nucleophile. Key words: [S.sub.N]Ar reaction, Bronsted-type plot, Yukawa-Tsuno plot, zwitterionic intermediate, six-membered cyclic transition state. Resume : Nous presentons une etude cinetique des reactions [S.sub.N]Ar de 1-aryloxy-2,4-dinitrobenzenes (1a-1h) avec une serie d'amines secondaires cycliques dans un melange a 80 mol% eau - 20 mol% DMSO a 25,0 [+ or -] 0,1 [degrees]C. Les courbes de [k.sub.obsd] representees en fonction de la concentration d'amine s'incurvent vers le haut, sauf celles des reactions de substrats dont le groupe partant aryloxyde presente un substituant fortement electroattracteur avec la piperidine, une amine fortement basique. Les traces courbes indiquent que les reactions s'effectuent a la fois par des voies catalytiques et non catalytiques. Nous avons obtenu des courbes de type Bronsted lineaires pour les reactions non catalysee et catalysee du 1-(4-nitrophenoxy)-2,4-dinitrobenzene (1a), dont les coefficients [[beta].sub.nuc] sont de 0,84 et 0,78 respectivement. La courbe de Yukawa-Tsuno pour la reaction non catalysee des composes 1a-1h avec la piperidine presente une excellente correlation lineaire, dont les parametres [rho] = 1,66 et r = 0,31. En revanche, les constantes de vitesse des reactions catalysees sont independantes de la nature electronique du substituant present sur le groupe partant. Nous avons pose l'hypothese que les reactions [S.sub.N]Ar en question procedent par un intermediaire zwitte-rionique (MC[+ or -]) qui se partage en produits par des voies catalytiques et non catalytiques. Nous avons conclu que la reaction catalytique de l'intermediaire MC[+ or -] s'effectue via un mecanisme concerte en passant par un etat de transition cyclique a six membres ([ET.sub.cycl]) plutot que via un mecanisme sequentiel, passant par un intermediaire anionique discret (MC), qui est le mecanisme traditionnellement admis. Nous abordons les effets du milieu sur la reactivite et le mecanisme de reaction. Notamment, les liaisons hydrogene entre les amines et les molecules d'eau empechent la formation de dimeres, favorable sur le plan cinetique, qui est observee dans certains solvants aprotiques; aucun role explicite de l'eau dans l'etat de transition de la voie catalytique n'est necessaire ni n'est propose. L'absence de la voie catalytique dans la reaction des systemes (1a-1c) avec la piperidine comme nucleophile s'explique par la stabilisation specifique des groupes partants aryloxydes portant des substituants fortement electroattracteurs. [Traduit par la Redaction] Mots-cles : reaction [S.sub.N]Ar, courbe de type Bronsted, courbe de Yukawa-Tsuno, intermediaire zwitterionique, etat de transition cyclique a six membres., Introduction In the toolkit of the synthetic organic chemist involved in the design and preparation ofnew aromatic compounds, nucleophilic aromatic substitution on electron-deficient substrates is a versatile, even essential, implement. [...]

In this study, the adsorption behaviors of methanol, methanal, toluene, ethylbenzene, and styrene molecules in FAU, FER, CON, and MWW zeolites were investigated. The adsorption isotherms of the five adsorbates in the four zeolites at 298 and 350 K were simulated using grand canonical Monte Carlo simulations. Moreover, binary component adsorptions were considered. The results revealed that the saturated adsorption capacity ofsingle components in different zeolites decreased in the order of FAU > MWW > CON > FER, and the adsorption capacity of the five adsorbates in the same zeolite decreased in the order of methanal > methanol > toluene > styrene > ethylbenzene. The equilibrium adsorption capacity slightly decreased with increasing temperature. In terms of binary component adsorption, intense competition existed between the smaller adsorbed molecules. As the differences among the molecular structures increased, the competition in adsorption became more intense. Key words: zeolite, adsorption, grand canonical Monte Carlo simulation, adsorption isotherm, molecular simulation. Dans le cadre des present travaux, nous avons etudie le comportement d'adsorption des molecules de methanol, de methanal, de toluene, d'ethylbenzene et de styrene sur des zeolites de structure FAU, FER, CON et MWW. Nous avons simule les isothermes d'adsorption des cinq adsorbats sur les quatre zeolites a 298 K et a 350 K en utilisant la methode Monte-Carlo dans l'ensemble grand canonique. En outre, nous avons etudie le cas des adsorptions de composantes binaires. En ce qui concerne les composantes uniques, les resultats ont revele que la capacite de saturation de leur adsorption sur differentes zeolites diminuait selon l'ordre FAU > MWW > CON > FER et que la capacite d'adsorption des cinq adsorbats sur une meme zeolite diminuait selon l'ordre methanal > methanol > toluene > styrene > ethylbenzene. La capacite d'adsorption a l'equilibre diminuait legerement en fonction de l'augmentation de la temperature. En ce qui concerne l'adsorption de composantes binaires, la competition pour l'adsorption etait plus forte entre les molecules de plus petite taille. A mesure que la difference entre les structures moleculaires augmentait, la competition pour l'adsorption s'intensifiait. [Traduit par la Redaction] Mots-cles: zeolite, adsorption, simulation de Monte-Carlo dans l'ensemble grand canonique, isotherme d'adsorption, simulation moleculaire., Introduction Styrene is an important monomer that is industrially applied for the synthesis of plastics and rubbers. (1) It is traditionally synthesized from benzene and ethylene, which is a complicated [...]

Abstract: (benzene)Cr[(CO).sub.3] was claimed to be more aromatic than benzene, based on the central [.sup.1]H Me chemical shifts in dimeth-yldihydropyrene annulated to it. In this paper, several dihydropyrenes are computationally [...]

Abstract: The crystal structure of 4-Methyl-N-(1-phenylethyl)-N'-(1-phenylethylidene) benzene sulfonohydrazide is disclosed, which is obtained from direct reaction between acetophenone tosylhydrazone and potassium tert-butoxide. Reaction mechanisms and the corresponding energy barriers were [...]

Monoalkyl esters of benzene-1,2-dicarboxylic (phthalic) acid have not been reliably characterized by analytical parameters for their chromatographic and chromatospectral identification. Mass spectra of a series of monoalkyl phthalates (R = [C.sub.1]-[C.sub.8]) are discussed; their gas chromatographic retention indices on the RTX-5 polydimethylsiloxane stationary phase (5% phenyl groups) are determined. A linear dependence of indices on the number of carbon atoms in n-alkyl fragments of molecules and a correlation between the indices of any monoalkyl phthalates and corresponding diesters were used for the control of the data obtained. Using the last correlation, we found that most part of index values of mono (2-ethylhexyl) phthalate given in literature is wrong and, therefore, the results of identification of this compound in various samples must be revised. It was found that simplest monoalkyl phthalates are unstable during gas chromatographic separation, which may result in distortions of their mass spectra. To compare with monoalkyl phthalates, a similar series of monoesters of (Z)-butenedioic (maleic) acid was characterized. Retention indices of monoalkyl phthalates in reversed phase HPLC were determined and discussed. Keywords: phthalic acid, maleic acid, monoalkyl esters, gas chromatographic retention indices, reversed phase HPLC, mass spectrometry, Present-day chromatographic and chromatospectral identification of organic compounds in complex mixtures implies a comparison of their mass spectra and chromatographic retention parameters (indices) with reference data. Algorithms of such comparison [...]

Now that we have completed our discussion of benzene rings and the infamous 'benzene fingers,' the next topic on our hydrocarbon hit parade is carbon-carbon double bonds. C=C bonds, otherwise [...]

Following up on the last installment, we examine the infrared (IR) spectra of mono- and disubstituted benzene rings. We examine numerous example spectra and learn how the position of C-H [...]

The objective of this study was to examine the potential for beneficial reuse of fly ash as a sorbent for benzene, trichloroethylene, and ethylbenzene in soils treated with cement (i.e., cement-based solidification/stabilization (S/S)). Batch testing was performed with soil-cement mixtures containing fly ash and compared with similar samples with humic acid as a source of organic carbon. The experimental batch test results were fit to the Freundlich sorption model assumingboth linear and nonlinear behavior. It was found that the level of sorption is low for benzene and trichloroethylene, but relatively higher for ethylbenzene. Cement addition appeared to not only decrease sorption values obtained for fly ash, but also eliminate the nonlinear sorptive behavior, likely due to the blocking-coating of sorption sites. To demonstrate the practical application of the sorption observed, a hypothetical contaminated site is modeled with a one-dimensional contaminant transport program. It iss shown that the addition of fly ash can potentially reduce off-site migration of trichloroethylene (TCE), but is more effective at reducing ethylbenzene migration, for the time frames considered in the modeling. Key words: fly ash, cement, sorption, volatile organic compounds (VOCs), stabilization, solidification. L'objectif de cette etude est d'evaluer le potentiel de reutilisation des cendres volantes en tant que sorbant pour le benzene, trichlorethylene et ethylbenzene dans des sols traites avec du ciment (solidification/stabilisation (S/S) avec du ciment). Des essais en batch ont ete realises avec des melanges sol-ciment contenant des cendres volantes, et par la suite ont ete compares a des echantillons similaires avec de l'acide humique comme source de carbone organique. Les resultats des essais en batch ont ete associes au modele de sorption de Freundlich en supposant un comportement lineaire et non-lineaire. Il a ete observe que le niveau de sorption est faible pour le benzene et le trichlorethylene mais relativement eleve pour l'ethylbenzene. L'ajout de ciment semble diminuer les valeurs de sorption obtenues pour les cendres volantes et aussi eliminer le comportement en sorption non-lineaire, probablement en raison du blocage-enveloppement des sites de sorption. Pour demontrer l'application pratique de la sorption observee, un site contamine hypothetique est modelise avec un programme de transport de contaminants en une dimension. Il est demontre que l'ajout de cendres volantes peut potentiellement reduire la migration hors du site de trichlorethylene (TCE), mais est plus efficace pour reduire la migration de l'ethylbenzene, pour les periodes de temps considerees dans la modelisation. [Traduit par la Redaction] Mots-cles: cendres volantes, sorption, composes organiques volatils (COV), stabilisation, solidification., Introduction The use of cement or other binder materials to solidify and (or) stabilize contaminants present in soils has been used extensively in the USA and the UK as a [...]

[TiCl.sub.4]-mediated Friedel-Crafts benzylation of benzene with 8-(bromomethyl)[2.2]metacyclophanes to afford 8-benzyl[2.2] metacyclophanes is described. Substituent effect through space on the rate of the benzylation of benzene with a bromomethyl group attached on the opposite aromatic ring was first found in this investigation. Interestingly, the introduction of the substituents at the internal position 16 tends to promote the present benzylation reaction rate 1.8-3.8 times. It was found that the benzyl cation intermediate was stabilized by the the direct through-space cation-πt interaction among the opposite benzene ring in the benzylation of [2.2]metacyclophane systems. Key words: cyclophanes, Friedel-Crafts benzylation, benzyl cation intermediate, through-space electronic interaction. On decrit la reaction de benzylation du benzene par le 8-bromomethyl)[2,2]metacyclophanes par la meethode de Friedel-Crafts catalysee par le [TiCl.sub.4]. Dans ce travail, on a mis en evidence pour la premiere fois, un effet de substituant qui se fait sentir a travers l'espace sur la vitesse de benzylation du benzene en raison d'un groupe bromomethyle attacheee sur le noyau aromatique oppose. Il est interessant de noter que l'introduction de substituants a la position interne 16 tendent a acceterer les vitesses de reaction de benzylation par des facteurs allant de 1,8 a 3,8. On a trouvee que le cation benzylique intermeediaire est stabilise; par une interaction cation-π directe a travers l'espace du noyau benzeenique oppose dans la benzylation de systemes [2,2] meetacyclophanes. Mots-cles: cyclophanes, benzylation suivant Friedel-Crafts, cation benzylique intermeediaire, interaction electronique a travers l'espace., Introduction The geometry of the [2.2]metacyclophane ([2.2]MCP) skeleton is known in detail from an X-ray structural analysis. (2,3) The crystal consists of discrete molecules, each of which has a center [...]

Commercial dodecylbenzene cable fluid was aged at temperatures of 105 and 135 [degrees]C in dry oxygen-free nitrogen. In addition, selected samples were aged at 135 [degrees]C under sealed conditions where air was excluded from the headspace above the oil. A variety of analytical techniques, such as ultra-violet visible and infra-red spectroscopy, acid number and water content measurements, were then used to characterize the aged oils. In addition, their electrical properties were assessed by dielectric spectroscopy. Compared with ageing in air, the ageing rate was reduced significantly and, as expected, no major oxidation peaks were detected in the infrared spectrometer. Significantly, very little absorbance at 680 nm ('red absorbers') was detected in samples aged with copper and, consequentially, no large increases in dielectric loss were recorded within the ageing times considered here. This study compliments previous investigations on cable fluid and 1-phenyldodecane aged in air and show that the same ageing indicators are valid in oils aged under conditions which more closely resemble those found in high voltage plant. Index Terms--Ageing, optical spectroscopy, dielectric properties, dodecylbenzene fluid, DDB fluid, cable oil.

An Fe[Cl.sub.3]-mediated intramolecular heterocyclization of 3-alkoxyimino-2-arylalkylnitriles is applied to prepare a series of functionalized N-alkoxyindole-3-carbonitrile derivatives. The novel synthetic method allows the N-moiety on the side chain to be annulated to the benzene ring as the final synthetic step which in turn facilitates the functionalization of the benzenoid portion of the indole at an early stage of the synthesis.

Br fragment in photodissociation of o-, m-, and p-bromofluorobenzene at 266 nm is investigated using velocity imaging technique combined with (2!) resonance-enhanced multiphoton ionization (REMPI). The obtained translational energy distributions suggest that the Br fragments are generated through two dissociation channels.

The solvation characteristic of ketocyanine dye is studied by monitoring the absorption band of the dye in two ternary solvent mixtures. The maximum energy of absorption (E) of the dye, in both ternary and binary solvents mixtures are found to be deviated significantly from the mole fraction average of the E values in the component solvents.

The synthesis, isolation, and characterization of hexakis(4-(N-butylpyridylium))benzene as both a hexacation and neutral molecule are reported.

A novel microelectromechanical device has been developed to study the details of the heat transfer mechanisms involved at the nucleation site for the nucleate boiling process. This device enables quantifying the magnitude, time period of activation, and specific areas of influence of different mechanisms of heat transfer from the surface with a resolution several times greater than previously reported. This is achieved through the use of an array of embedded temperature sensors within a carefully designed dual-layer (silicon and benzocyclobutene) wall which allows for the accurate calculation of local heat flux, circumventing difficulties encountered when using existing methods. The sensors are radially distributed around the nucleation site. Heat is supplied to the wall by a thin film heater fabricated on the outer nonwetted surface. Single bubbles are generated at the center of the array while the temperatures and the bubble images are recorded with a sampling frequency of 8 kHz. The temperature data provided the necessary thermal boundary conditions to numerically calculate the surface heat flux with an unprecedented radial resolution of 22-40 [micro]m. Fabrication, characterization, and the ability of the developed device to elucidate the heat transfer aspects of the nucleation process are demonstrated. [2007-0016] Index Terms--Boiling, bubble, heat transfer.

The N-H bond dissociation energy in benzamide in the gas phase is calculated to explain the thermochemical properties of benzoylnitrene radical anion.

The synthesis and characterization of 1,4-difluorobenzo[c]phenanthrene (1,4-DFBcPh) was carried to understand its extent of DNA binding by the metabolities of dihydrodiol and diol epoxides. The findings showed that increased molecular distortion decreased metabolic activation to the terminal metabolities and the formation of diol epoxide metabolites was the DNA-damaging species.

The synthesis and characterization of a new class of highly fluorescent and stable carbazole-based dendrimers that contain the ethynylbenzene and diethynylbenzene cores are presented. The results have indicated the dendrimers potential use as blue-emitting materials in organic light-emitting diodes (OLEDs).

Several new ferrocene derivatives bearing two donor-acceptor systems are reported in which the ferrocene unit has acted both as a donor group and as a rotating spacer. These ferrocene sensors have allowed the naked-eye selective colorimetric detection of copper[II] cation and of benzoate, acetate, or cyanide anions, all anions of special toxicological and biological relevance.

Photochromic systems can convert light energy into mechanical energy, thus they can be used as building blocks for the fabrication of prototypes of molecular devices that are based on the photomechanical effect. Hitherto a controlled photochromic switch on surfaces has been achieved either on isolated chromophores or within assemblies of randomly arranged molecules. Here we show by scanning tunneling microscopy imaging the photochemical switching of a new terminally thiolated azobiphenyl rigid rod molecule. Interestingly, the switching of entire molecular 2D crystalline domains is observed, which is ruled by the interactions between nearest neighbors. This observation of azobenzene-based systems displaying collective switching might be of interest for applications in high-density data storage. scanning tunnel microscopy | molecular switches | photochromic system | data storage

The dilational properties of hydroxy-substituted alkyl benzenesulfonates are studied by using oscillating the bubble method at water-air and water-decane interfaces. The structural changes in surfactant influence the distinct maxima in dilational modulus vs time curves in some cases.

The composition of AMP and concentrations of samples are analyzed to study the inclusion complexes in solution of CD and AMP and the viscosity of these mixtures. The higher concentrations of these solutions show increased viscosity and large cluster formation and a significant response to UV and visible spectra which is not observed in the dilute solutions.

The atomic Cl kinetics was monitored by using the laser flash photolysis resonance fluorescence technique. The kinetic isotope effects in both directions support the mechanism for the reaction of phenyl with HCl with a recommended rate constant for Cl benzene derived from high-temperature measurements and data at room temperature.

The ab initio calculations were performed to investigate the gas-phase reactivity of cycloheptatrienyl and indenyl radicals. It was found that the reaction of the cycloheptatrienyl radical with atomic hydrogen could lead to its fast conversion into the more stable benzyl radical which involves the reaction pathway for intermediate formation of heptatriene, norcaradiene and toluene.

1,3,5-Triethylbenzene and pyrogallol are used for the synthesis of new tripodal receptor bearing three catechol subunits on a benzene platform and the binding ability of the tricatecholic receptor for carbohydrate detection is examined. The results have shown that the tripodal catecholic receptor binds the octyl glycosides with different affinities and with a 6-fold selectivity factor of the [alpha]-mannoside over the [beta]-glucoside.

The dimers involving benzene or other substituted [pi] systems were investigated to examine the relevance of the magnitudes of their attractive and repulsive interaction energy components in governing the geometries of several [pi]-[pi] systems. The findings suggest that the presence of substituents on the aromatic ring, irrespective of their electron withdrawing or donating nature leads to an increase in the binding energy.

The laser-induced fluorescence spectrum of 3-vinyl-1H-indene is presented along with a theoretical analysis based on density functional and configuration interaction calculations. The negative identification of 3-vinyl-1H-indene as the carrier of the mass 142 spectrum has made the identification of species arising from the discharge of benzene in argon very interesting.

A study is conducted to demonstrate that equatorial 4-O-benzyl ethers are removed with moderate selectivity on exposure to dichlorodicyanoquinone in wet dichloromethane at room temperature in the presence of other benzyl ethers in glycopyranosides and glycothiopyranosides. It is inferred that selective cleavage of the 4-O-benzyl ethers derives from antiperiplanar nature of C4-O4 and C5-O1 bonds maximizes the electron-withdrawing properties of the latter and hastens the decomposition of the radical cation.

The feasibility of ruthenium-catalyzed cyclization of 2-alkyl-1-ethynylbenzenes through benzene 1,5-hydrogen shift activated by a cationic ruthenium-vinylidine intermediate is studied. It is found that catalytic cyclization of 2-alkyl-1-ethynylbenzene derivatives has formed 1-substituted-1H-indene products.

The binary mixtures containing quaternary phosphonium salt- tetrabutylphosphonium methanesulfonate and alcohols or alkylbenzenes were analyzed for solid-liquid phase and liquid-liquid phase equilibria. The aromatic hydrocarbons were used to detect the immiscibility of solid-liquid equilibria with immiscibility in the liquid phase.

Experimental and computational were used to study the reaction of benzene-tropothione and identify three equimolar isomeric products. The findings suggest that the biradical character of the benzyne has a key role in the present reaction.

Emission from charge recombination between radical cations and anions of various tetrakis(phenylethynyl)-benzenes (TPEBs) were measured during pulse radiolysis in benzene (Bz). The three types of charge-transfer pathways suggest that the emission spectra of TPEBs with intramolecular charge transfer (ICT) character depend on the substitution pattern and the various kinds of donor and acceptor groups during pulse radiolysis in Bz.

A study was conducted to examine the reactions of 1,3-disubstituted isobenzofurans with the fullerene [C.sub.60] in the context of an approach to open a large orifice on the fullerene framework. The thermal stability of the adducts toward retro-Diels-Alder fragmentation differs greatly in solution from that in the solid state which suggest that they could be stored at room temperature in the solid state for several weeks without significant decomposition but have to be handled within several hours in solution.

The systematic investigation of in-plane hydrogen-bonded complexes of ammonia with partially substituted fluorobenzenes has shown that fluorobenzene, difluorobenzene and trifluorobenzene have favored the formation of cyclic complexes with a C-H...N-H...F-C binding motif. The tendency with which fluorobenzenes adapt to the C-H...N-H...F-C binding motif has decreased with the progressive fluorination of the benzene ring and has disappeared completely when benzene ring is substituted with five or more fluorine atoms.

The singlet excited states and doublet ionized/electron-attached states of o-benzoquinone (o-BQ) are analyzed by using the symmetry adapted cluster (SAC)/SAC-configuration interaction (SAC-CI) method. The SAC-CI theoretical spectra have showed that it is essential to take electron correlation into account when describing the singlet and doublet excited states of o-BQ.

An efficient protocol is described for the synthesis of structurally diverse (diphenylphosphinoylmethyl)benzenes. The transformation and elaboration of 4-bromo-1,3-bis(diphenylphosphinoyl)benzene through the transition-metal-mediated procedures has produced functionalized (diphenylphosphinoylmethyl)benzenes.

The regeneration of a series of 2,3-dihydrobenzo[b]selenophene-5-ol derivatives by water-soluble N-acetylcysteine in a two-phase model system for lipid peroxidation is investigated. The results have shown that the regeneration and catalytic performance is dictated by the number and position of methyl substituents present in the phenolic ring of the antioxidant.

An efficient protocol is described for the synthesis of structurally diverse (diphenylphosphinoylmethyl)benzenes. The transformation and elaboration of 4-bromo-1,3-bis(diphenylphosphinoyl)benzene through the transition-metal-mediated procedures has produced functionalized (diphenylphosphinoylmethyl)benzenes.

The electrosynthesis, isolation and characterization of reaction products between [C.sub.60.sup.2-] and benzyl bromide in PhCN are reinvestigated. The visible and near-infrared spectra of the monoanion and dianion of 1,2-[(PhC[H.sub.2]).sub.2][C.sub.60] are described.

A quantitative structure-property relationship (QSPR) study is presented for exploring the physical properties of catafusenes (cata-condensed benzenoids). Cata-condensed benzenoid hydrocarbons have some physical properties that depend in large measure on the presence of linearly condensed benzenoid rings that is parameter n and bulk properties that reflect in a large measure the weak intermolecular forces.

Van der Waals (vdW) complexes of aromatic moieties are investigated to understand the intermolecular interaction between some small molecules (HF, [H.sub.2]O, N[H.sub.3], and C[H.sub.4]) and certain benzenoid ring system. The point dipole-quadrupole and point quadrupole-quadrupole interactions found in the complexes have accounted for the preferred orientations and the distributed multipole moments of the constituent atoms are found to give a quantitative description of the interaction in such complexes.

A cationic rhodium(I)/Segphos complex has catalyzed an enantio- and diastereoselective intermolecular [2+2+2] cycloaddition of 1,2-bis(arylpropiolyl)benzenes with various monoalkynes in order to produce axially chiral 1,4-teraryls possessing an anthraquinone structure. A thermal intramolecular [4+2] cycloaddition of 1,2-bis(arylpropiolyl)benzenes has proceeded at 60 [degree]C to produce aryl-substituted naphthacenediones in moderate to good yields.

A new two-photon (TP) probe for the detection of free [Mg.sup.2+] ions in living cells and live tissues was developed. This probe can be excited by 880nm laser photons and is capable of imaging endogenous stores of free [Mg.sup.2+] in live tissues using TP microscopy.

The complex bioactive natural and unnatural benzopyran congeners were synthesized using one/two-step approaches. The congeners were synthesized by phenol directed intramolecular diastereoselective dipolar thermal/base catalyzed [2+] cycloaddition approach.

Azobenzene derivatives carrying a nitroxide radical (aminoxyl) were prepared and their photoisomerization reaction to the corresponding cis-isomers was investigated. The unsubstituted derivatives at the para position were found to undergo photoisomerizations by irrdiation and the intermolecular magnetic interactions were observed by structural change for each photochromic couple.

The influence of solvent, temperature and viscosity on the photoautomerization processes of a series of o-hydroxyarylbenzazoles is examined. All the compounds, including 2-(3'-hydroxy-2'-pyridyl)benzoxazole (HPyBO), have undergone an excited-state intramolecular proton transfer (ESIPT) from the hydroxyl group to the benzazole N3 to yield an excited tautomer in syn conformation.

One-electron oxidation of alcohols such as methanol, ethanol and 2-propanol by 1,3,5-trimethoxybenzene radical cation ([TMB.sup..+]) in the excited state ([TMB.sup..+]*) is observed during the two-color two-laser flash photolysis. The analysis has shown that the hole of transfer from [TMB.sup..+]* to alcohols is initiated by the selectively excitation of [TMB.sup..+] in solution by using the two-color two-laser photolysis technique.

The rearrangement of n(n = 1,...,19) Ar atoms around [Na.sup.+]-benzene clusters and an atom-bond potential energy surface are used to study the gradual evolution from cluster rearrangement to solvation dynamics. The results have shown that benzene molecule is strongly bound to [Na.sup.+] independently of the number of solvating rare-gas atoms, although due to the anisotropy of the interaction potential, the Ar atoms solvate the [Na.sup.+]-benzene cluster preferentially on the side of the cation.

Potential energy curves are produced for the halogen bonding interactions of several halobenzene-formaldehyde complexes. The results have shown that for most halogen substituents, a halobenzene and formaldehyde form stable halogen bonded complexes with interaction energies that increase as the size of the halogen substituent increases.

The synthesis, photochromism, and optical properties of a chiral heliconoid diarylethene that shows a large change in specific optical rotation induced by photochromism is reported. The diarylethene possessing one [4]thiaheterohelicene and one benzothiophene with a chiral methoxymethoxyethyl group on its C-3 position was proved to work as a switch of specific optical rotation at a wavelength at which both colored and colorless forms have no absorption in solution.