L. H. Klemm

Determination and mutagenic activity of nitrogen-containing thiophenic compounds in coal-derived products

Abstract Polycyclic aromatic compounds containing both nitrogen and sulphur heteroatoms in aromatic rings were determined in a coal-derived liquid and a coal tar by capillary column gas chromatography and gas chromatography-mass spectrometry. G.c. with a flame photometric detector was used to analyse the nitrogen-containing polycyclic aromatic compound fraction obtained by adsorption chromatography on neutral alumina. The four possible isomers of the azadibenzothiophenes, and various other azathiophenic compounds, were positively identified by comparison with retention data of newly synthesized standard compounds. The aminodibenzothiophenes were the major nitrogen/sulphur-containing heterocycles in the coal liquid, while the azathiophenic compounds were the major ones in the coal tar. The differences between the two coal-derived products were related to the reaction conditions during their production. The four isomers of the azadibenzothiophenes were assayed for mutagenicity using the Ames test and compared with the mutagenicities previously reported for the aminodibenzothiophenes. It was found that the azadibenzothiophenes were not mutagenic, as opposed to the aminodibenzothiophenes.

Syntheses of Tetracyclic and Pentacyclic Condensed Thiophene Systems

Publisher Summary This chapter summarizes the syntheses of various tetracyclic and pentacyclic condensed thiophene systems. The close physicochemical analogies between the benzene and thiophene rings are discussed. There are many advantages of using the thienolog correlation. Perhaps the most important advantage is that one can use the structural formulas of the known and predicted polycyclic aromatic hydrocarbons as a point of reference for writing the structures of all of the numerous condensed thiophenes that are theoretically possible. Most commonly, tetracyclic and pentacyclic condensed thiophenes are synthesized by the process of annulation, i.e., by constructing one or more rings onto a precursor molecule by an intermolecular or intramolecular process. Thus, most of the synthetic methodologies are categorized first in terms of the nature of the ring produced, whether a sulfur heterocyclic ring or a carbocyclic one, and second in terms of the reagents or the type of reaction used. A few synthetic methods that do not fit neatly into one of the annulations categories are also discussed in the chapter.

13C-NMR SPECTRAL DATA FOR SUBSTITUTED THIENO[2,3-b]- AND THIENO[3,2-b]PYRIDINES AND THE CORRELATION OF IPSO SUBSTITUENT CHEMICAL SHIFTS

The C NMR chemical shifts in CDCI3 for the parent thieno[2,3-b]and thieno[3,2-b]pyridines and 44 of their monosubstituted derivatives are reported. Linear correlations of ipso substituent chemical shifts in these compounds and in the corresponding benzene derivatives are found and are compared with reported data for compounds with substituted pyridine or thiophene rings. In the two thienopyridine systems the slope of the correlation line characterizes the position of substitution with respect to the heteroatom in the substituted ring. Introduction Various research groups obtained C NMR spectra of a number of simple monosubstituted thiophenes (1,2), pyridines (3), thienothiophenes (4), and isoquinolines (5). These workers directed special attention to the ipso substituent chemical shift (ISCS), i.e. the difference in chemical shifts between the substituted carbon atom in the derivative and that in its parent compound (with Η attached to the carbon). Meanwhile, literature ISCS values for monosubstituted benzenes were accumulated in a table by Ewing (6), who noted that theoretical calculations were inadequate to account for these data (7). Nonetheless, as shown in references 1-5, if one keeps the solvent and the position of substitution on the heterocyclic ring constant one obtains a linear plot for ISCS for the heterocyclic system versus ISCS for the same array of substituents in the benzene system. In the present paper we report C NMR data for chemical shifts in the parent system thieno[2,3-to]pyridine 1 and 25 of its derivatives 2-2S, as well as the parent system thieno[3,2-b]pyridine 22 and 19 of its derivatives 2S-4S (see Tables 1 and 2). Data derived from ISCS plots are also presented (see Tables 3 and 4).

X-RAY CRYSTALLOGRAPHIC STUDIES OF FOUR MONOSUBSTITUTED THIENOPYRIDINES. COMPARISON OF EXPERIMENTAL DATA WITH CALCULATED OR MEASURED VALUES FOR THE PARENT COMPOUNDS

X-ray crystallographic data are reported for thieno[3,2-b]pyridine-2-carbonitrile (lb), thieno[3,2c]pyridine-4-carbonitrile (2b), 3-acetylaminothieno[2,3-c]pyridine (3b). and ethyl thieno[2,3-b]pyridine-3-carboxylate (4b). All of the thienopyridine ring systems are planar with internal bond angles of 90.7 ± 0.6° for C-S-C and 115.9 ± 1.9° for C-N-C. C -S and C-N bond lengths in the rings are 1.73 ± 0.02 Ä and 1.34 ± 0.02 Ä, respectively. Comparison is made of our measured data with bond angles and lengths calculated from molecular orbital theory for the parent unsubstituted compounds la, 2a, and 4a and for reported experimental data for parent 3a. In general, numerical values are remarkably close in the corresponding a and b systems. C Nmr spectral data are also reported for 2b-4b.

Kinetics of reduction of cinnamaldehyde by means of hydrido- and deuteridocobalt tetracarbonyl

The reaction of HCo(CO)4 (HT) or DCo(CO)4 (DT) with excess cinnamaldehyde (CA) in methylcyclohexane (RH) at 22.2° and under 1 atm of CO follows pseudo-first-order kinetics in HT or DT with an inverse isotopic effect of 0.54. Identified products of the reaction are hydrocinnamaldehyde (HCA) and styrene (STY). The STY is believed to be an artifact of the thermal decomposition of the true product PhCH2CH2C( (DOUBLE BOND) O)Co(CO)4 (X) or its isomer. Reduction of the carbon-carbon double bond in CA is effected by hydrogen from both the cobalt compound and RH. It is proposed that the reaction involves a free-radical chain mechanism in which the rate of the slow step is proportional to [CA], the initial molar concentration of CA raised to a power of 1.5− 1.8. Additionally the rate of conversion of CA to HCA and X meets the criteria of a homocompetitive reaction with [CA], [HCA], and [STY] simple functions of t0.5 (where t is reaction time) for use of DT or (in a single case) a function of (t0.5 + t) for use of HT.

Thin-layer and gas chromatography of some fluorobiphenyls and fluoronaphthalenes

Abstract Relative retention data are reported for biphenyl, naphthalene, seven fluorine substituted biphenyls (bearing 1, 2, 8, and 10 fluorine atoms per molecule), and mono- and octafluoronaphthalenes in gas chromatography with (a) silicone fluid DC 710, (b) Carbowax 20M, and (c) Bentone 34-silicone fluid DC 710 and in thin-layer chromatography on (d) silica gel and (e) alumina. With a and d retention generally decreases with increasing number of fluoro substituents, n , and, for a given n , is higher for a biphenyl compound than for a naphthalene one. 2,2′-Difluorobiphenyl is an exception in d, since it has the smallest R F of the various solutes. Some irregularities in these trends are found in cases b, c and e.

Intermolecular methyl group transfers in the xylene and xylene—benzene systems by means of anhydrous HF

Abstract Treatment of xylene with anhydrous HF (200 wt.%) at 180°C for 2 h in a sealed bomb gives disproportionation to toluene ( A , 42%) and trimethylbenzenes ( B , 32%). Extension to use of xylene—benzene mixtures for the hydrocarbon component gives transmethylation wherein yields of A and B (maxima of 30% and 27%, respectively) are found to vary with hydrocarbon composition, weight percentage of HF used, reaction temperature, reaction pressure, and addition of inorganic salts.