Investigation of Heterogeneous Reactions of PAH's on Particle Surfaces Using Laser Microprobe Mass Analysis

Abstract

Artificially generated NaCl particles were coated with PAH's by using a condensation technique. These particles were exposed to reactive gases like ozone, bromine and nitrogen dioxide. The original as well as the exposed particles were investigated by fluorimetric analysis and by LAMMA (Laser Microprobe Mass Analysis) in the desorption mode, which allows the evaporation and characterization of surfaces of single particles. The results are interpreted in terms of possible heterogeneous atmospheric reactions. The reactivity of the considered PAH's towards nitrogen dioxide was found to be negligible. The structure of the reaction products formed with ozone was partially elucidated.     

Enhanced Fluorescence And Room Temperature Liquid Phosprorescence Detection In Pseudophase Liquid Chromatography (Plc)

Abstract

The effect of a micellar mobile phase on the fluorescence detection of a variety of polynucleararomatic hydrocarbons (PAH's) separated via HPLC is examined. It was found that the “fluorescence peaks” of the separated PAH's were enhanced up to ten times by the sodium dodecylsulfate micellar mobile phase. Furthermore, one can use room temperature liquid phosphorescence detection when the mobile phase consists of a deoxygenated aqueous solution of thallium and sodium dodecylsulfate micelles. The phosphorescence intensity was relatively weak and difficult to obtain compared to the fluorescence.     

Identification and Differentiation of Isomeric Methylated Derivatives of Oxygenation Products of Polycyclic Aromatic Hydrocarbons by Gas Chromatography - Mass Spectrometry

Abstract

An isomeric pair of compounds is obtained from 4-car-boxyaldehydephenanthrene-5-carboxylic acid (1) by various methods routinely applied for the methylation of acidic oxygenation products of K-region polycyclic aromatic hydrocarbons (PAH's) prior to GC and GC/MS analysis. Differentiation of the individual cyclic and acyclic isomers, a classical general problem, proves possible by careful analysis of the mass spectral fragmentation patterns in the representative case studied here.     

Coupling micro-LC and capillary GC as a powerful tool for the analysis of complex mixtures

A multidimensional chromatography system with a packed fused silica Micro-LC column connected on-line with capillary gas chromatography is presented. The Micro-LC column is used for group separation. Whole peaks are injected into the capillary GC column via an on-column injector. The reproducibility of the proposed transfer system for polyaromatic hydrocarbons is 3% to 7% relative standard deviation. The potential of this on-line Micro-LC-GC system is demonstrated by the analyses of PAH's and of a complex light gasoline fraction.     

Detectors for Liquid Chromatographic Analysis for Polynuclear Aromatic Hydrocarbons

Abstract

A number of liquid chromatographic detectors of various types have been evaluated for both selectivity and sensitivity for the detection of polynuclear aromatic hydrocarbons (PAH). Detection limits for fixed and variable wavelength UV photometers, filter fluorimeters, and spectrofluorimeters have been determined. The utility of each of these types of detectors for use in the reversed-phase HPLC analysis of environmental extracts containing trace levels of PAH's is discussed.     

Effects of Different Stationary Phases and Surfactant or Cyclodextrin Spray Reagents on the Fluorescence Densitometry of Polycyclic Aromatic Hydrocarbons and Dansylated Amino Acids

Abstract

The detectable luminescence of twelve dansy1 amino acids and four polycyclic aromatic hydrocarbons (PAH's) spotted on five common TLC stationary phases was evaluated. The detectable luminescence varied appreciable for compounds associated with different stationary phases. The use of surfactant and cyclodextrin spray reagents caused luminescence enhancements on some stationary phases but not others. The reagents did not affect all compounds to the same degree indicating that qualitative information could be obtained in some cases. The largest luminescence increase for a compound spotted on silica gel was for pyrene (i.e., 47-fold) sprayed with sodium cholate. The degree to which the plates were dried also affected the luminescence intensity. Possible reasons for the observed effects are discussed.     

Sorption Tubes Packed with Polydimethylsiloxane: A New and Promising Technique for the Preconcentration of Volatiles and Semi-Volatiles from Air and Gaseous Samples

This paper is concerned with the determination of volatile and semi-volatile organic components in air and gaseous (headspace) samples, focusing primarily on polar analytes. Samples were analyzed by preconcentration on different (ad)sorbents followed by thermal desorption and analysis by capillary gas chromatography. The performance of a cartridge filled with 100% polydimethylsiloxane (PDMS) particles was compared to that of adsorbents like Tenax TA and Carbotrap 300. Though the PDMS phase is non-polar it showed adequate retention for both polar and non-polar components. The blank runs of the PDMS trap were significantly better than those of most adsorbents and did not deteriorate, as was the case with all the conventional adsorbents investigated. With respect to trapping efficiencies, the PDMS phase performed better for most of the analytes under investigation compared to the adsorbents. For a range of analytes including triethylamine, butanone, diacetyl, nicotine, and acetic acid the PDMS phase performed exceptionally well whereas all adsorbents showed unsatisfactory performance. The packed PDMS traps were employed for the determination of organic acids, PAH's and nitro-PAH's in air and for the analysis of the headspace of cacao and hop.     

Enantioselective Reduction of 2-Ketoalkanephosphonate by Baker's Yeast

Bioreduction of 2-oxo-3-halo (or azido) alkanephosphonates and 4-ethoxy-4,2-dioxobutanephosphonates by baker's yeast afforded 3-substituted 2-hydroxyalkanephosphonates in moderate to good yields and ee value. Moreover, a regio- and stereoselective bioreduction of 2,3-dioxoalkanephosphonates and 2,4-dioxoalkanephosphonates by baker's yeast was studied also. The resulting chiral hydroxy compounds can be used as chirons for the stereoselective synthesis of biologically active molecules.     

Aldolic Condensations on Inorganic Solid Support: Application to the Synthesis of O-Ethyl Esters of 3-Phenyl-2-propenethioic Acids

Aldolic condensations with 0-ethyl thioesters are performed on basic alumina to give 2,3-unsaturated thioates. The stereochemistry of the reaction is discussed and compared with Knoevenagel's, Pinner's and Wittig-Horner's reactions.     

Heterocyclization reaction of 2‐(2‐methylaziridin‐1‐yl)‐3‐ureidopyridines under appel's conditions

The reaction of 2‐(2‐methylaziridin‐1‐yl)‐3‐ureidopyridines 12 with triphenylphosphine, carbon tetra‐chloride, and triethylamine (Appel's conditions) led to the corresponding carbodiimides 13 , which underwent intramolecular cycloaddition reaction with aziridine under the reaction conditions to give the pyridine‐fused heterocycles, 2,3‐dihydro‐1H‐imidazo[2′,3′:2,3]imidazo[4,5‐b]pyridines 16 and 12,13‐dihydro‐5H‐1,3 ‐benzodiazepino [2′,3′:2,3] imidazo[4,5‐b]pyridines 17 .     

The synthesis of thiaolivacine and related compounds

1,5-Dimethylbenzothieno[2,3-g]isoquinoline (thiaolivacine) has been prepared from the nitro-vinyl derivative of 4-methyl-3-dibenzothiophenecarboxaldehyde. Using the same aldehyde, 4-des-methylisothiaolivacine was prepared by formation of the Schiff's base with aminoacetaldehyde diethyl acetal followed by cyclization. Similar methods yielded the pyrido-N-isomer, 1-des-methylthiaolivacine, from 4-methyl-2-dibenzothiophenecarboxaldehyde. The thiaolivacine parent unsubstituted ring system, benzothieno[2,3-g]isoquinoline, was prepared from 2-dibenzothio-pheneearboxaldehyde by the aminoacetaldehyde approach, as was the corresponding oxygen analog, benzofuro[2,3-g]isoquinoline, from 2-dibenzofurancarboxaldehyde. The 100 MHz spectra of these fused isoquinolines are recorded and correlated.     

A Practical Synthesis of Chiral 3-Chloro-2-hydroxyalkanoates and 2,3-Epoxyalcohols

Asymmetric reduction of 3-chloro-2-oxoalkanoates with baker's yeast gave optically active 3-chloro-2-hydroxyalkanoates with ≥95% e.e. in most cases, which were converted to optically active 2,3-epoxyalcohols with ≥78.0% e.e.     

Amphiphilic Cyclodextrin Complexation of Clofazimine

The cyclodextrin amphiphilesheptakis[6-(1'-sulfonato-3'-propyl)-6-thio-2,3-di-O-acetyl]-β-cyclodextrin,heptakis[6-(6' -sulfonato-2'-benzimidazolyl)-6-thio-2,3-di-O-acetyl]-β-cyclodextrin, and heptakis[6-(β-D-glucosyl)-6-thio-2,3-di-O-acetyl]-β-cyclodextrin have been shown to form aggregates in water by fluorescencemeasurements on the binding of 2-anilinonaphthalene, and by laserlight-scattering measurements. Estimates of aggregation number have been obtained.These aggregates successfully incorporate clofazimine, a lipophilic heterocyclic drug,and increase its water solubility by a factor of 30 to 50.     

Cyclisation of 7-Deazaxanthine-9-propionic Acid to an Active-Site-Directed,Irreversibly Acting Inhibitor of Xanthine Oxidase

Phase-transfer alkylation of 2,4-dimethoxy-7H-pyrrolo[2,3-d]pyrimidine ( 2 ) with ethyl 3-bromopropionate leads regioselectively to ethyl 2,3-dimethoxy-7H-pyrrolo[2,3-d]pyrimidine-7-propionate ( 3a ). After saponification and ether cleavage, the functionalised 7-deazaxanthine 4b was obtained. Reaction of 4b with H₂O-soluble carbodiimide resulted in an intramolecular acylation at N(3) with formation of the tricyclic compound 5 . Compound 5 - bearing a reactive lactam ring - is an active-site-directed, irreversibly acting inhibitor of xanthine oxidase from cow's milk.     

Synthesis of pinacol esters of 2,3-alkadienylboronic acid via the copper(I) mediated coupling reaction of Knochel's (dialkoxyboryl)methylzinc reagents with propargylic tosylates

The reaction of propargyl tosylates (1) with (dialkoxyboryl)methyl-copper(I) reagents, prepared in situ from Knochel's (dialkoxyboryl)-methylzinc iodide (2) and CuCN · 2LiCl, produced 2,3-alkadienyl-boronates (3) in moderate yields. The reaction proceeded regioselectively to provide an S_N2' substitution product without contamination by other products such as 3-alkynylboronate.     

Cyclocondensation of 3(2H)-benzo[b]thiophenone and oxidation products obtained during these reactions

The cyclocondensation of 3(2H)-benzo[b] thiophenone under acidic conditions has been studied. The symmetrical cyclotrimer tris(benzo[b]thieno)[2,3:2',3':3',2']benzene was formed and under certain conditions also a rearranged cyclotrimer, tris(benzo[b]thienyl)[2,3:2',3':3',2']benzene.The formation of cyclotrimers was accompanied by oxidative coupling products involving the initially formed dimeric compound, 3-hydroxy-2,3-bibenzo[b]thienyl. During several of these reactions, a novel heterocycle, tris(benzo[b]thieno)[3,2-b:2',3'-d:2',3'-f]oxepin, was formed. The products were studied by mass spectrometry and fragmentation pathways were determined by a linked scanning technique.     

Synthesis of fluorantheno[1,2-b]thiophene and fluorantheno[3,2-b]thiophene,isosteres of benzofluoranthenes

The total syntheses of fluorantheno[1,2-b]thiophene and fluorantheno[3,2-b]thiophene are reported. The common cyclobutanone intermediate which was obtained by [2 + 2] addition of fluorenylidene ketene with 2,3-dihydrothiophene underwent regioselectively α or β ring opening to lead to linear or angular PAC skeleton molecules under desired conditions. 2,3-Dichloro-5,6-dicyanobenzoquinone was applied for aromatization to achieve the formation of PAC's. These two isosteres exhibit very similar uv/visible spectra to benzo[a] and [b]fluoranthenes respectively. Spectroscopic data used for their structural assignments is also discussed.     

One-stage synthesis of condensed pyrimidines by reaction of substituted 3-(pyrimidin-5-yl)propanoic acids with <Emphasis Type="Italic">ortho</Emphasis>-diamines: Extension of limits

By condensation of 2-aryl-substituted pyrimidin-5-ylpropanoic acids with 1,2-ethanediamine and 1,2-benzenediamine in polyphosphoric acid new derivatives of heterocyclic systems were synthesized: imidazo- and benzo[4',5']imidazo[1',2':1,6]pyrido[2,3-d]pyrimidines. Unlike that the reaction of substituted 2-mercaptopyrimidin-5-ylpropanoic acid with 1,2-benzenediamine in polyphosphoric acid in the presence of equimolar amount of ZnCl₂ proceeds by a tandem mechanism with the formation of 4-methyl-5,6-dihydrobenzo[4',5']imidazo[1',2':1,6]pyrido[2,3-d]pyrimidine-2-thiol and the corresponding disulfide.     

Bifunctionalized Allenes. Part VIII. An Efficient and Varied Method for the Synthesis of 2-Sulfonylated Alka-2,3-Dienoates

Abstract

An efficient and varied method for the synthesis of 2-sulfonylated alka-2,3-dienoates by intermediate formation of allenecarboxylates, allenyl sulfones, and propargyl sulfinates using the relatively high acidity of the hydrogen atom at the allenic C-1 atom and the [2,3]-sigmatropic rearrangement is described.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Synthesis of pyrido[2,3-d]pyrimidinones by the reaction of aminopyrimidin-4-ones with benzylidene meldrum's acid derivatives

A series of pyrido[2,3-d]pyrimidine-4,7-diones 5a-h were prepared from 6-amino-4-pyrimidones 1 and benzylidene Meldrum's acid derivatives 2 by cyclization reactions in boiling nitrobenzene. The structure of 5, determined by nmr measurements, reveals a selective orientation of 1 and 2 in the addition step.