Polycyclic Aromatic Hydrocarbons In Solution Research Articles

Photophysical and Photochemical Studies of Polycyclic Aromatic Hydrocarbons in Solutions Containing Tetrachloromethane. III. Photochemical Interaction of Excited Polycyclic Aromatic Hydrocarbons with Tetrachloromethane in Two-Component Mixtures

Abstract In the photoreactions of polycyclic aromatic hydrocarbons with tetrachloromethane in binary mixtures of tetrachloromethane with cyclohexane, benzene and acetonitrile, both the quenching of the fluorescence and the photoreactions run through an intermediate stage which is an exciplex of the excited hydrocarbon with tetrachloromethane. Abnormal quantum yields of the hydrocarbon decrease are interpreted in terms of the appearance of a new reaction channel via a triplex consisting of the excited hydrocarbon, solvent and tetrachloromethane. The photoreaction is quenched by diphenylpicrylhydrazyl, thus suggesting the radical nature of the chemical transformations. A kinetic scheme is suggested for the photophysical and photochemical processes describing the observed phenomena.

Polycyclic Aromatic Hydrocarbon Solute Probes. Part IX: Evaluation of Additional Pentaphene, Pentacene, and Pyranthrene Compounds as Possible Solvent Polarity Probes

Fluorescence emission spectra are reported for benzo[rst]dinaphtho[2,1,-8,7defg;2′1′8′,7′ijkl]pentaphene, dibenzo[a,rst]naphtho[8,l,2cde]pentaphene, dibenzo[fg,ij]pentaphene (also called dibenzo[b,n]perylene), dibenzo[de,kl]naphtho[l,2,3,4rst]pentaphene, dibenzo[h,rst]pentaphene, pyranthrene, tetrabenzo[de,hi,op,st]pentacene, and dinaphtho[2,l,8,7de fg;2′,l′,8′,7′opqr]pentacene dissolved in various organic solvents. Results of these measurements are used to screen PAHs for potential solvent polarity behavior. Of the eight PAHs examined, only dibenzo-[h,rst]pentaphene exhibited probe behavior as evidenced by selective, systematic emission intensity enhancement of band I with increasing solvent polarity.

Polycyclic Aromatic Hydrocarbon Solute Probes. Part VIII: Evaluation of Additional Naphthacene and Perylene Derivatives as Possible Solvent Polarity Probe Molecules

Fluorescence emission spectra are reported for phenanthro[5,4,3,2efghi]perylene, dibenzo[cd,k]naphtho[8,1,2fghi]perylene, benzo[b]peryiene, dibenzo[e,ghi]perylene, and benzo[a]naphtho[8,1,2cde]-naphthacene dissolved in various organic solvents. Results of these measurements are used to screen PAHs for potential solvent polarity behavior. Of the five PAHs studied, only phenanthro[5,4,3,2efghi]perylene exhibited probe behavior, as evidenced by selective emission intensity enhancement of band I with increasing solvent polarity.

Fluorescence Emission Properties of Polycyclic Aromatic Compounds in Review

Abstract Fluorescence emission behavior of polycyclic aromatic hydrocarbons (PAHs), polycyclic aromatic nitrogen heterocycles (PANHs), polycyclic aromatic sulfur heterocycles (PASHs) and benzofluoranthenes dissolved in organic solvents of varying polarity is reviewed. Measured fluorescence properties are used to divide aromatic solutes into two categories, probe and nonprobe molecules, depending upon whether the molecule's emission intensity ratios vary systematically with solvent polarity. Seventeen polycyclic aromatic hydrocarbon solute probes are identified and possible probe character versus molecular structure correlations are examined. Also discussed are instrumental and chemical artifacts associated with accurate determination of fluorescence emission intensities.

Fast Atom Bombardment Combined with Mass Spectrometry or Characterization of Polycyclic Aromatic Hydrocarbons

A new approach using fast atom bombardment combined with mass spectrometry to characterize polycyclic aromatic hydrocarbons (PAHs) in the range of 128–252 u molecular weight is described. Sulfolane was employed as a liquid matrix for these π-conjugated hydrocarbons. Bombardment of sulfolane solution of certain PAHs with an atom beam produces both radical cation (M +∓) and protonated molecule [(M + H) +], with no evidence of fragmentation. Collisional activation of the fast atom bombardment-desorbed M +∓ ions, however, results in several structure-specific fragment ions. Structural differences in a few isomeric hydrocarbons can be detected using the [(M + H) +]/[M +∓] abundance ratio and in the pyrene-fluoranthene pair by the B/E linked-field-collision-activated dissociation data. The [(M + H) +]/[M +∓] was found to be compound-specific and correlated well with certain properties (resonance energy, proton affinity, and ionizing energy) of PAHs.

Destruction of Polycyclic Aromatic Hydrocarbons with Ultrasound

Abstract Dilute ethanol-water solutions of a few polycyclic aromatic hydrocarbons, a dioxin, and neat chlorinated solvents were sonicated and then characterized by UV-visible absorption spectrophotometry and laser excited Shpol'skii spectrometry. The results indicate that all the compounds were destroyed on sonication leaving a carbonaceous residue.

Polycyclic Aromatic Hydrocarbon Solute Probes. Part VII: Evaluation of Additional Coronene Derivatives as Possible Solvent Polarity Probe Molecules

Fluorescence emission spectra are reported for dinaphtho[8,1,2abc; 2′,1′,8′klm]coronene, naphtho[8,1,2abc]coronene, naphth[2′,1′,8′,7′: 4,10,5]anthra[1,9,8abcd]coronene, dibenzo[bc,ef]coronene, benzo[1,2,3bc;4,5,6b′c′]dicoronene, anthra[2,3a]coronene, dinaphtho-[8,1,2abc;2′,1′,8′jkl]Coronene, and tetrabenzo[de,hi,mn,qr]naphthacene dissolved in n-hexadecane, butyl acetate, dichloromethane, and acetonitrile. Results of these measurements are used to screen PAHs for potential solvent polarity probe behavior. Of the eight PAHs studied, only naphtho[8,1,2abc]coronene, dinaphtho[8,1,2abc;2′,1′,8′klm]-coronene, and anthra[2,3a]coronene were classified as probe molecules. The fluorescence spectra of the first two PAHs show selective enhancement of the I band emission intensity in polar solvents. For anthra-[2,3a]coronene, the measured ratio of emission intensities of bands I and II decreased systematically with increasing solvent polarity.

Polycyclic Aromatic Hydrocarbon Solute Probes. Part VI: Effect of Dissolved Oxygen and Halogenated Solvents on the Emission Spectra of Select Probe Molecules

Fluorescence emission properties of pyrene, benzo[ ghi]perylene, coronene, and ovalene dissolved in carbon tetrachloride, chloroform, and dichloromethane are reported. Measurements indicate that the emission intensities of select solutes are time dependent, and suggest that the polycyclic aromatic hydrocarbon molecule undergoes a photochemical reaction with the chlorinated solvent. The effect of dissolved oxygen on the experimental ratio of emission intensities is also reported.

Polycyclic Aromatic Hydrocarbon Solute Probes. Part V: Fluorescence Spectra of Pyrene, Ovalene, Coronene, and Benzo[ghi]perylene Dissolved in Liquid Alkylammonium Thiocyanate Organic Salts

Fluorescence properties of pyrene (Py), benzo[ghi]perylene (BPe), coronene (Co), and ovalene (Ov) dissolved in n-butylammonium thiocyanate, sec-butylammonium thiocyanate, and dipropylammonium thiocyanate are reported. Solvent polarities of the thiocyanate salts are estimated from the fluorescence emission intensity ratios of bands I and III (i.e., Py = I/III) of the polycyclic aromatic hydrocarbon vibronic spectra. Calculated BPe, Co, and Ov values indicate that all three thiocyanate salts are comparable in polarity to cyclohexanone.

Polycyclic Aromatic Hydrocarbon Solute Probes. Part IV: Effect of Solvent Polarity on the Fluorescence Emission Fine Structures of Select Pyrene and Pentaphene Derivatives

Fluorescence properties of benzo[e]pyrene, benzo[a)pyrene, dibenzo[a,ejpyrene (naphtho[1,2,3,4def]chrysene), 1-chloropyrene, tribenzo[de, kl,rst]pentaphene, dinaphtho[2,1,8,7defg,2′,1,8′,7'ijkl]pentaphene, benz [rst]anthra[9,1,2cde]pentaphene, and dibenzo[fg,ij]phenanthro[2,1,10,9,8,7pqrstuv]pentaphene dissolved in solvents of varying polarity are reported. Measurements indicate that emission intensities of benzo[e)pyrene (BePy) and dibenzophenanthropentaphene (DBPP) depend on solvent polarity. Two new polarity scales are defined, BePy = I/IV and DBPP = I/II, on the basis of the ratio of the fluorescence intensities of select vibronic bands. For fluorescence spectra for the remaining six compounds studied, either the spectra were not clearly resolvable or the calculated intensity ratios remained nearly constant, irrespective of solvent polarity.

Comparison of the gas-chromatographic properties of mesomorphic polymeric stationary phases

The gas-chromatographic properties of two mesomorphic polysiloxane (MEPSIL) stationary phases, one smectic (SB) and the other nematic (N), were investigated. The retention indices and separation factors (relative retentions), α, of several pairs of polycyclic aromatic hydrocarbon (PAH) and fatty acid methyl ester (FAME) isomer solutes were used to gauge differences in the selectivity provided by each. The heats of solution of the PAH showed that the smectic MEPSIL is more selective for solutes with different length-to-breadth ratios. Also, five peaks were resolved for sixcis andtrans octadecenoic FAME isomers with this solvent. The nematic MEPSIL, on the other hand, was found to be more useful at higher temperatures because of its higher clearing point. In addition, solute capacity factors were smaller than those observed with the smectic MEPSIL, as evidenced by lower retention indices. The former was therefore more useful for the analysis of high molecular-weight PAH.

Polycyclic Aromatic Hydrocarbon Solute Probes. Part III: Fluorescence Emission Spectra of Pyrene, Ovalene, Benzo[ghi]perylene, and Coronene Dissolved in Liquid Tetrabutylammonium Sulfonate Salts

Article on polycyclic aromatic hydrocarbon solute probes and fluorescence emission spectra of pyrene, ovalene, benzo[ghi]perylene, and coronene dissolved in liquid tetrabutylammonium sulfonate salts.

Polycyclic aromatic hydrocarbon solute probes. Part II. Effect of solvent polarity on the fluorescence emission fine structures of coronene derivatives.

The fluorescence properties of coronene (Co), benzo[a]coronene (BCo), naphtho[2,3-a]coronene (NCo), dibenzo[a,j]coronene (DCo), naphtho[1,2,3,4-ghi]perylene, benzo[pqr]naphtho[8,1,2-bcd]perylene and dibenzo[cd,lm]perylene dissolved in solvents of varying polarity are reported. Measurements indicated that the emission intensities of the four coronene derivatives depended on solvent polarity. The Co, BCo and NCo scales have been defined as the ratio of the fluorescence intensities of bands I and III of the vibronic spectra. Band III of dibenzo[a,j]coronene was not clearly identifiable in all the solvents studied, and the DCo scale was therefore defined as the intensity ratio of band I and IV. Emission intensity ratios of the three perylene derivatives remained nearly constant, irrespective of solvent polarity.

Optimization of the gas chromatographic separation of five-membered ring polyarenes with an admixed BPhBT liquid crystal—dexsil 300 stationary phase

A window diagram constructed with the liquid crystal BPhBT in admixtures with the gum phase Dexsil 300 gave the optimum mixing ratio for the gas chromatographic resolution of five-membered ring polycyclic aromatic hydrocarbon solutes. The window diagram was constructed from relative retention data obtained from specific retention volume measurements. Plots of the specific retention volumes versus percentage of BPhBT in the blend were linear to within ± 5% for all solutes. Further, intimately blended phases gave specific retention volumes virtually identical with those of mechanically mixed phases, within experimental error, when the same mixing ratios were compared. This suggests that the liquid crystal is only dispersed (as opposed to dissolved) in Dexsil 300 and that the two phases act independently of each other in the blends. This contention is supported by differential scanning calorimetric measurements. The use of the retention index scheme for the purpose of window diagram construction is shown not to be a valid option for this system.

Photophysical and Photochemical Studies of Polycyclic Aromatic Hydrocarbons in Solutions Containing Tetrachloromethane II. The Solvent Effect on the Fluorescence Quenching of Aromatic Hydrocarbons by Tetrachloromethane

Fluorescence quenching of aromatic hydrocarbons in a large concentration range of the quencher has been studied in a variety of two-component mixtures of tetrachloromethane with other solvents. In aliphatic solvents the process could be described by the Stern-Volmer equation, whereas in the remaining mixtures the fluorescence quenching curves showed a parabolic behaviour which has been explained in terms of specific interactions between the components of the mixtures.

Photophysical and Photochemical Studies of Polycyclic Aromatic Hydrocarbons in Solutions containing Tetrachloromethane. I. Fluorescence Quenching of Anthracene by Tetrachloromethane and its Complexes with Benzene, p-Xylene and Mesitylene

Fluorescence quenching of anthracene has been studied in two-component mixtures of CCl4 with cyclohexane, benzene, p-xylene and mesitylene. Non-typical quenching curves have been found in mixtures containing benzene and its derivatives.

Formation of nitroarenes from the reaction of polycyclic aromatic hydrocarbons with dinitrogen pentoxide

Download Hi-Res ImageDownload to MS-PowerPointCite This:Environ. Sci. Technol. 1985, 19, 11, 1115-1121

Cytotoxicity of fine particles with and without adsorbed polycyclic aromatic hydrocarbons using Chinese hamster lung cells (V79)

The cytotoxic effects of coal fly ash (CFA) and wood charcoal, with and without adsorbed polycyclic aromatic hydrocarbons (PAH), were compared to the cytotoxicity of alumina and silica particles in V79 cells. Particle uptake was confirmed using light and scanning electron microscopy (SEM). Cellular toxicity was determined by clonal survival following a 6-day exposure to CFA and wood charcoal particles, with and without adsorbed pyrene and benzo( a)pyrene (BaP), and to alumina and silica. Particle concentrations needed to produce a 50% reduction in survival were used to compare cytotoxic endpoints. Clonal survival decreased in a dose-response fashion as particle concentration increased. Silica and alumina were the most toxic particles, followed by charcoal and CFA was the least toxic. Differences in the chemical nature of the particle surfaces and the amount of adsorbed toluene-soluble mater were hypothesized to influence the observed cytotoxicities of the different particles. Adsorption of pyrene on CFA had minimal effect on the cytotoxicity of the CFA. Pyrene adsorption had little or no effect on charcoal cytotoxicity. The toxic effect of charcoal was increased following adsorption of 50 × 10 −12 moles of BaP/ μg particle. Generally, the toxicity of the particle with adsorbed PAH was less than the sum of the toxicity due to particle alone plus the same concentration of PAH in solution.

Thermodynamics of solutions of polycyclic aromatic hydrocarbons studied by gas—liquid chromatography with a nematic and an isotropic stationary phase

Thermodynamic solution parameters of the isomeric polycyclic aromatic hydrocarbons phenanthrene and anthracene at infinite dilution in the nematic liquid crystal N,N′-bis( p-methoxybenzylidene)-α,α′-bi- p-toluidine (BMBT) and in its isotropic analogue N,N′-bis( p-methoxybenzylidene)-4,4′-diaminodiphenylmethane (BMBDM) have been derived by gas—liquid chromatography. The unique selectivity exhibited by BMBT towards isomeric polycyclic aromatic hydrocarbons is explained in the light of a current solution theory in terms of differences in the partial molar enthalpies and entropies of solution. Differences in solution behaviour between BMBT and BMBDM are examined with infinite-dilution solute activity coefficient, partial molar excess enthalpy and entropy data.

Determination of the solubility behavior of some polycyclic aromatic hydrocarbons in water

The dynamic coupled column liquid chromatographic (DCCLC) method for determining the solubility of polycyclic aromatic hydrocarbons (PAH) in water is described. The DCCLC technique is a very rapid, precise, and accurate method for determining the aqueous solubility behavior of sparingly soluble organic compounds. The agreement of PAH aqueous solubilities and calculated solubility parameters, such as ..delta..Hs, with values that have been previously reported in the literature helps to confirm the validity of this approach. In all cases replicate solubility measurements of the generated PAH solutions at constant temperature were better than +- 3 percent and in most cases better than +- 1%. The lack of an appropriate physical parameter for accurately extrapolating PAH solubilities further enhances the utility of DCCLC method.