Vibrational spectra of C60.C8H8 and C70.C8H8 in the rotor-stator and polymer phases

C(60).C(8)H(8) and C(70).C(8)H(8) are prototypes of rotor-stator cocrystals. We present infrared and Raman spectra of these materials and show how the rotor-stator nature is reflected in their vibrational properties. We measured the vibrational spectra of the polymer phases poly(C(60)C(8)H(8)) and poly(C(70)C(8)H(8)) resulting from a solid-state reaction occurring on heating. On the basis of the spectra, we propose a connection pattern for the fullerene in poly(C(60)C(8)H(8)), where the symmetry of the C(60) molecule is D(2h). On illuminating the C(60).C(8)H(8) cocrystal with green or blue light, a photochemical reaction was observed leading to a product similar to that of the thermal polymerization.     

C. M. C., counterion binding and thermodynamics of ethoxylated anionic and cationic surfactants

Summary The properties of a series of ionic ethoxylated surfactants of the typeR _m (OC₂H₄) SO₄Na andR _m (OC₂H₄) TAB (m = 10, 12, 14 or 16 andx = 0, 1, 2 or 3) were studied. Surface areas obtained from surface tension measurements increased as the ethoxy group number increased whereas increasing the hydrocarbon chain length had little effect. The c.m.c.'s obtained from conductivity decreased with increase in hydrocarbon chain length and to a smaller extent as the ethoxy group number increased. Values ofG° showed the methylene group to be four fold as effective as the ethoxy group in promoting micellisation. As the temperature was varied between 5 and 60 °C all the surfactants exhibited a minimum c.m.c. value close to 25 °C which decreased as the surfactant became more hydrophobic and increased as the surfactant became more hydrophilic. Counterion binding from specific ion electrode measurements increased with increase in hydrocarbon chain length but decreased with increase in ethoxy group number. Counterion binding decreased with increase in temperature.

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Zusammenfassung Die Eigenschaften einer Reihe ionischer äthoxylierter oberflächenaktiver Stoffe vom TypR _m (OC₂H₄) SO₄Na undR _m (OC₂H₄) TAB (m = 10, 12, 14 oder 16 undx = 0, 1, 2 oder 3) wurden untersucht. Die bei der Messung der Oberflächenspannung ermittelten Werte verzeichneten eine Zunahme bei der Zunahme der Äthoxy-Gruppe, wohingegen die Verlängerung der Kohlenwasserstoffkette keine nennenswerten Auswirkungen zeigte. Die durch Leitfähigkeit erhaltenen c.m.c.'s verringerten sich bei der Verlängerung der Kohlenwasserstoffkette und, in etwas geringerem Maße, beim Anwachsen der Äthoxy-Gruppe. Meßwerte vonG° deuteten darauf hin, daß die Methylengruppe in der Steigerung der Micellisierung um das Vierfache wirksamer war als die Äthoxy-Gruppe. Zwischen 5° und 60° zeigten alle untersuchten oberflächenaktiven Stoffe ein Minimum im c.m.c.-Wert in der Nähe von 25°, das sich verringerte, wenn diese Stoffe hydrophober wurden, und zunahm, wenn sie hydrophiler wurden. Die Bindung von Gegenionen, die aus Messungen mit spezifischen Ionenelektroden gewonnen wurde, steigerte sich mit zunehmender Länge der Kohlenwasserstoffkette, aber ging zurück mit zunehmender Zahl der Äthoxy-Gruppen. Die Bindung von Gegenionen verringerte sich mit steigender Temperatur.

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With 7 figures and 4 tables     

Separation of phenotypically indistinguishable Candida species, C. orthopsilosis, C. metapsilosis and C. parapsilosis, by capillary electromigration techniques

At the current state of laboratory diagnostics, methods for fast identification of phenotypically indistinguishable species are difficult or inaccurate. An example is represented by Candida parapsilosis, which is the second most common yeast species isolated from bloodstream infections. C. parapsilosis comprises a complex of three genetically distinct groups. Genotypes II and III have been designated as the separate species Candida orthopsilosis and Candida metapsilosis, phenotypically indistinguishable. The considerable genetic variability of these newly described yeasts species has caused difficulties in the development of molecular techniques for their precise identification. Similarly, the detection of biofilm formation, which is considered as an important yeast virulence factor, is accompanied by difficulties. In this study we optimize the first precise and reproducible method for the separation and possible identification of C. orthopsilosis, C. metapsilosis and C. parapsilosis as well as the detection of their ability to form biofilm. The method is based on capillary isoelectric focusing and capillary electrophoresis with UV detection. In capillary isoelectric focusing, very narrow pH gradients were established. With such gradients, differences in isoelectric points of biofilm-negative and biofilm-positive species calculated from the migration times of the selected pI markers were below 0.03 pI units. In the capillary zone electrophoresis narrow zones of the cells of Candida species were detected with sufficient resolution. The values of the isoelectric point and the migration velocities of the examined species were independent on the origin of the tested strains. Capillary isoelectric focusing was examined also for the separation and detection of the cultivated biofilm-negative C. parapsilosis in the blood serum.     

Electrochemistry of thiols and disulfides. 11: D.C., A.C. and differential pulse polarography of glutathione]

Flame emission and atomic absorption procedures are described for determination of aluminum in typical sulphide and silicate minerals and in representative ores and slags. Sodium peroxide fusion was the most satisfactory of three dissolution procedures used. Optimum flame types, background correction, and the addition of sample concomitants to the comparison standards are discussed.     

Numerical simulation of C/C/C planar X-ray waveguides.

A numerical simulation was done to check the possibility of using planar C/C/C multilayers with density contrast 0.2 and 0.7 g/cm3 as an X-ray waveguide. After an optimization procedure, suitable waveguide layer thicknesses were found which provide a high degree of resonant standing wave field intensity enhancement in the core layer at incident beam energy of 13 keV. The obtained results were compared with those of the Mo/Be/Mo waveguide, whose high waveguiding capability at the same energy value was reported in the 1990s. The comparison shows that standing wave field intensity resonant enhancement provided by C/C/C planar multilayers is very high and, consequently, a guided beam can be well detected.     

H. C. Brown

“As mentioned below, I had rough times and frustating moments during my first year at Purdue. However, nothing has been more frustating than the fact that the Nobel Committee has kept mistreating H. C. Brown. While there can be chemists who are worthy of all prizes except Nobel Prize, H. C. Brown is definitely not one of them.”     

Linear ketenimines. Variable structures of C,C-dicyanoketenimines and C,C-bis-sulfonylketenimines

C,C-dicyanoketenimines 10a-c were generated by flash vacuum thermolysis of ketene N,S-acetals 9a-c or by thermal or photochemical decomposition of alpha-azido-beta-cyanocinnamonitrile 11. In the latter reaction, 3,3-dicyano-2-phenyl-1-azirine 12 is also formed. IR spectroscopy of the keteniminines isolated in Ar matrixes or as neat films, NMR spectroscopy of 10c, and theoretical calculations (B3LYP/6-31G) demonstrate that these ketenimines have variable geometry, being essentially linear along the CCN-R framework in polar media (neat films and solution), but in the gas phase or Ar matrix they are bent, as is usual for ketenimines. Experiments and calculations agree that a single CN substituent as in 13 is not enough to enforce linearity, and sulfonyl groups are less effective that cyano groups in causing linearity. C,C-bis(methylsulfonyl)ketenimines 4-5 and a C-cyano-C-(methylsulfonyl)ketenimine 15 are not linear. The compound p-O2NC6H4N=C=C(COOMe)2 previously reported in the literature is probably somewhat linearized along the CCNR moiety. A computational survey (B3LYP/6-31G) of the inversion barrier at nitrogen indicates that electronegative C-substituents dramatically lower the barrier; this is also true of N-acyl substituents. Increasing polarity causes lower barriers. Although N-alkylbis(methylsulfonyl)ketenimines are not calculated to be linear, the barriers are so low that crystal lattice forces can induce planarity in N-methylbis(methylsulfonyl)ketenimine 3.     

C45- und C50-Carotinoide. 5. Mitteilung

C₄₅- and C₅₀-Carotenoids. Synthesis of an Optically Active Cyclic C₂₀-Building Block and of (2R,2′S)-3′,4′-Didehydro-1′,2′-dihydro-2-(4-hydroxy-3-methylbut-2-enyl)-2′-(3-methylbut-2-enyl)-β,ψ-caroten-1′-ol (= C. p. 473) The synthesis of the optically active C₂₀-building block (R)- 16 and of the optically active C₅₀-carotenoid C.p. 473 ( 1 ) starting from (?)-β-pinene is reported.     

Comparability graphs and molecular properties III. C9 and C10 alkanes

The graph-theoretical approach recently developed for comparing and ordering isomeric chemical compounds is extended and applied to the calculation of various molecular properties of C₉ and C₁₀ alkanes (critical densities, volumes, and pressures; heats and entropies of vaporization; standard entropies in liquid and gas state). The key to the approach is in specifying subsets of comparable isomers which are located in the same paths in the so-called comparability graphs. Optimized samples for structure-property correlations are thus obtained.