Optical crystallographic properties of organic compounds

Summary The optical crystallographic properties of coumarin (I), salicylanilide, chlorothymol, and neocinchophen, all used in medicine or related fields, have been determined. These constants are useful in the identification of these compounds. It has been shown that both, chlorothymol and thymol, can be identified in mixtures of these two substances. Salicylanilide shows very strong negative birefringence, whereas coumarin and chlorothymol both show strong and moderately strong positive birefringence, respectively.

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Zusammenfassung Die kristalloptischen Eigenschaften von Cumarin (I), Salioylanilid, Chlorthymol und Neocinchophen, vier Verbindungen, die medizinisch von Interesse sind, wurden bestimmt. Die optischen Konstanten sind für die Erkennung dieser Substanzen nützlich und es wird darauf hingewiesen, daß Chlorthymol und Thymol in Mischungen dieser beiden Verbindungen erkannt werden können. Salicylanilid zeigt sehr starke negative Doppelbrechung, während Cumarin (I) und Chlorthymol stark bzw. mittelmäßig stark positiv doppelbrechend sind.

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Résumé On a déterminé les propriétés cristallographiques optiques de la coumarine (I), de la salicylanilide, du chlorothymol et du néocinchophène, produits employés en médecine. Ces constantes sont utiles pour l'identification de 764 R. N. Castle: Optical Crystallographic Properties of Organic Compounds. ces composés. On a montré que le thymol et le chlorothymol peuvent être identifiés dans les mélanges contenant ces deux substances. La salicylanilide possède une biréfringence négative très forte, tandis que la coumarine et le chlorothymol possèdent respectivement, une biréfringence positive forte et moyenne.

     

Determination of isotopically labelled monoesterphthalates in urine by high performance liquid chromatography-mass spectrometry

A method of analysis for monoesters of phthalic acid ('monoesterphthalates') in human urine has been developed. The method was needed to determine the hydrolysis and excretion efficiency of isotopically-labelled phthalate diesters ('phthalates') when they were fed to volunteers as part of a biomarker study to estimate total exposure to phthalates. The targeted substances were 13C-monobutylphthalate (MBP), 2H4-monobutylphthalate (MBP), 2H4-monobenzylphthalate (MBeP), 13C-monocyclohexylphthalate (MCHP), 13C-monoethylhexylphthalate (MEHP), and 13C-monoisodecylphthalate (MIDP). The monoesters in urine were deconjugated enzymatically, extracted into solvent, and then determined by high performance liquid chromatography-mass spectrometry (LC-MS) using atmospheric pressure chemical ionisation in the negative ion mode. The limits of determination were 10 ng ml(-1) for MBP, MCHP, MBeP and MEHP, and 40 ng ml(-1) for MIDP. The recovery from urine spiked at 100 ng ml(-1) was in the range from 70 to 85% except for MIDP which was lower at 55%. The between-batch reproducibility of the analysis was in the range 8 to 17% (n = 6 batches on separate days).     

Sensitivity factors,cross-section and resolution data for use with the Si Kα X-ray source

This paper describes the manufacture and use of a silicon Kα X-ray source giving a characteristic photon of energy 17 39.4 eV. Resolution and signal strength are given for the Au N₇, line. Sensitivity factors relative to the fluorine 1s peak are provided for 45 key elements. These data we are used to show that the transmission function of the ESCA 3 spectrometer (V.G. Scientific Ltd.) is close to the inverse of the function describing the inelastic mean free path over the kinetic energy range 170–1450 eV.     

Variation of the local field through the liquid-vapour interface

We derive an integral equation for the self-consistent local field E^loc(z) within an inhomogeneous non-polar fluid, with particular application to the liquid-vapour interface. Approximate solutions are given for the cases of induced atomic dipoles oriented perpendicular and parallel to the interface. For the perpendicular case we relate the average field to the local field and thus obtain an equation for the static dielectric constant ?(z) in terms of the density profile n(z). The departures of the local field from Lorentz form $\text{E}{}^{\mathrm{<mtext>ext</mtext>}}\text{/(1 + (}\text{8}\text{3}\text{)παn(z))}$ and of the dielectric constant from the Clausius-Mossotti form ($\text{1 + (}\text{8}\text{3}\text{)πan(z))/(1 ? (}\text{4}\text{3}\text{)παn(z))}$ are shown to be small. For the parallel case we discuss fringing of the external field and show that the dipoles align themselves with the average field, not the external field. The departure of the local field from $\text{E}{}^{\mathrm{<mtext>ave</mtext>}}\text{/(1 ? (}\text{4}\text{3}\text{παn(z))}$ is shown to be small.     

The synthesis of hydroxyphenylthiophenes

The synthesis of the five isomeric methoxyphenylthiophenes is described. The methoxy compounds were hydrolyzed to yield the hydroxyphenylthiophenes.     

Synthesis of monoamino and monohydroxydibenzothiophenes

The synthesis of the four monoaminodibenzothiophenes and the four monohydroxydibenzothiophenes is described.     

Stereoselective cascade reactions that incorporate a 7-exo acyl radical cyclization

[reaction: see text] Radical cascades that feature a 7-exo acyl radical cyclization followed by a 6-exo or 5-exo alkyl radical cyclization proceed with very good yields and diastereoselectivities. Two stereocenters are created by the reaction, and a single isomeric product was obtained from each of the five substrates examined. The relative configurations of the products are consistent with cyclizations occurring via chairlike or pseudochairlike transition states.     

Collaborative trial validation study of two methods, one based on high performance liquid chromatography-tandem mass spectrometry and on gas chromatography-mass spectrometry for the determination of acrylamide in bakery and potato products

A European inter-laboratory study was conducted to validate two analytical procedures for the determination of acrylamide in bakery ware (crispbreads, biscuits) and potato products (chips), within a concentration range from about 20 microg/kg to about 9000 microgg/kg. The methods are based on gas chromatography-mass spectrometry (GC-MS) of the derivatised analyte and on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) of native acrylamide. Isotope dilution with isotopically labelled acrylamide was an integral part of both methods. The study was evaluated according to internationally accepted guidelines. The performance of the HPLC-MS/MS method was found to be superior to that of the GC-MS method and to be fit-for-the-purpose.     

Determination of Dihydroxybenzenes in Plastic Food Packaging Materials and in Food Simulating Liquids Using Capillary Electrophoresis

A capillary electrophoresis method has been developed to determine 1,2-dihydroxybenzene and 1,3-dihydroxybenzene in the food simulants distilled water, 3% acetic acid, 15% ethanol, and olive oil. Both substances, used as monomers and additives to make food packaging plastics, could be analyzed within 15 min. The 1,4-dihydroxybenzene isomer was unretained and eluted with the electroosmotic flow, and so the CE method can give only a semi-quantitative estimate of this isomer if it is present as a migrant. The analytical recovery for the 1,2- and 1,3-isomers from spiked simulants was good at 87% to 98% except for 1,2-dihydroxybenzene which could only be recovered to the extent of 58% from olive oil. Calibration graphs were linear and the limit of detection for each substance was 0.6 mg/kg, which is well below migration limits for these substances. It is concluded that CE offers a rapid and reliable analysis for the control of migration from plastics intended for food contact which employ 1,2-dihydroxybenzene or 1,3-dihydroxybenzene during manufacture, and offers a screening method for 1,4-dihydroxybenzene migration.