Electron spin resonance studies of electron addition to 2-chloro- and 2-bromo-2-nitropropane

The products of electron addition to 2-chloro- and 2-bromo-2-nitropropane, which include their radical anions, have been detected by electron spin resonance spectroscopy.Radical anions of various aliphatic α-substituted nitro compounds have been proposed as reactive intermediates in radical-anion chain substitution reactions (S_RN1) (Scheme 1) and other related reactions.     

Determination of the melting point of porphyrins and other darkly coloured substances with the use of polarized light

Summary For determining the melting points of dark coloured substances, particularly porphyrins, by means of the micromelting point apparatus ofKofler, it is advantageous to illuminate with polarized light and to observe the material through an analyzing eyepiece. The property of birefringence in the solid state causes the material to shine brightly when the surrounding field is at maximum extinction. The moment melting occurs, this colour fades owing to dissolution of the crystal, but reappears on cooling when resolidification takes place. Double melting points may thus be observed with ease upon the same preparation.

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Zusammenfassung Will man die Schmelzpunkte dunkel gefärbter Substanzen, insbesondere von Porphyrinen, mittels derKoflerschen Mikroschmelzpunktsapparatur bestimmen, so ist es vorteilhaft, die Probe unter Beleuchtung mit polarisiertem Licht durch ein Analysatorokular zu beobachten. Infolge der Doppelbrechung im festen Zustand leuchtet die Probe hell, wenn das Gesichtsfeld ringsum das Extinktionsmaximum erreicht hat. Im Augenblick des Schmelzbeginns verblaßt diese Farbe infolge des Zerfließens des Kristalls, erscheint aber beim Erkalten wieder, wenn wieder Erstarrung eintritt. Auf diese Weise können Doppelschmelzpunkte an einem und demselben Präparat leicht beobachtet werden.

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Résumé Si l'on veut déterminer le point de fusion de substances de couleur foncée, surtout de porphyrines, avec le micro-appareil deKofler pour la détermination du point de fusion, il est pratique, d'éclairer la prise d'essai avec de la lumière polarisée et de l'observer avec un oculaire d'analyse. La réfraction double en état concret fait reluire la prise d'essai, tandis que le champ, qui l'entoure a atteint le maximum d'extinction. Au moment, où la fusion commence, la couleur disparait à cause de la dissolution du cristal, pour apparaitre de nouveau, quand la températur baisse et la matiére redevient solide. Ainsi on peut déterminer facilement des points de fusion doubles à la même pré-paration.

     

Radicals containing β-muonium and α or β substituents:

A range of radicals, CH₂(Mu) HX (1) and XCH(Mu)CR₂ (2), where X is a second-row substituent, have been studied by transverse-fieldμ ⁺SR spectroscopy. The reduced muon—electron hyperfine coupling constants (A′_Mu) for class (1) were all close to 37.3 G, the value for the parent radical CH₂(Mu)CH₂. However, for class (2)A′ _Mu values are greatly reduced, as is the case for the corresponding hydrogen derivatives, XCH₂CR₂, relative to CH₃CH₂. Nevertheless, the reduction in coupling for Mu in (2] is appreciably less that that for¹H in XCH₂CR₂ radicals, suggesting significant competition between Mu and X for the out-of-plane site. In addition to theμ ⁺ SR studies, the ESR spectra for the radicals (MeO)₃SiCHCH₃ and (MeO)₃SiCH₂CH₂ have been measured for comparative purposes.     

Electron spin resonance spectrum of radicals in γ-irradiated trimethyl phosphite: P(OMe)4, HP(OMe)3, P(OMe)2, (MeO)3P-P(OMe)3 + and H2COP(OMe)2

The infra-red spectra of 1 : 1 complexes between benzene and chlorine, bromine, and iodine chloride have been studied, with the complexes isolated in a nitrogen matrix at 20 K. The results are interpreted as evidence for an oblique complex structure, with the halogen molecule interacting mainly with one of the C=C bonds.     

On the mechanism of hydrogen atom and electron addition to phosphorus: An electron spin resonance study

A partir des spectres d'absorption du méthane naturel (1,1 pour cent de ¹³CH₄) enregistrés sur un spectromètre à grilles avec un parcours de 10 m, une pression de 10 torr et une résolution de 0,060 cm^-1, nous avons pu mesurer, avec une précision de pointé allant jusqu'à 0,004 cm^-1, 130 raies rotationnelles (correspondant à 150 transitions) de la bande ν₄ de la variété isotopique ¹³CH₄. Ces données ont permis de déterminer pour la première fois un jeu de treize constantes contribuant de façon significative à l'énergie jusqu'au quatrième ordre dans l'état vibrationnel v ₄=1. Pour les 150 transitions introduites dans le calcul, l'écart quadratique moyen est 0,020 cm^-1 et le plus grand écart n'excède pas 0,057 cm^-1. Les nombres d'ondes calculés sont donnés pour 233 transitions de la bande ν₄ de ¹³CH₄ allant de P 12 à R 13.     

Actuation of the Kagome Double-Layer Grid. Part 2: Effect of imperfections on the measured and predicted actuation stiffness

The actuation stiffness of a set of steel Kagome Double-Layer Grid (KDLG) structures with brazed joints is measured experimentally and compared with predictions by the finite element method. The predicted actuation stiffnesses for the perfect KDLGs much exceed the measured values, and it is argued that the low values of observed actuation stiffness are due to the presence of geometric imperfections introduced during manufacture. In order to assess the significance of geometric defects upon actuation stiffness, finite element calculations are performed on structures with a stochastic dispersion in nodal position from the perfectly periodic arrangement, and on structures with wavy bars. It is found that bar waviness has the dominant effect upon the actuation stiffness. The predicted actuation stiffness for the imperfect structures are in satisfactory agreement with the measured values assuming the same level of imperfection between theory and experiment.     

FT‐IR characterization and hydrolysis of PLA‐PEG‐PLA based copolyester hydrogels with short PLA segments and a cytocompatibility study

A series of the biodegradable copolyester hydrogels was prepared using a redox‐initiated polymerization with a constant 1:9 mole ratio of the Boltorn‐based acrylate and diacrylate triblock comacromonomers. The Boltorn® macromonomer was derived from the hyperbranched polyester Boltorn H20, which was functionalized at each terminus with poly(ethylene glycol) acrylate, and the diacrylate triblock macromonomer was poly (lactide‐b‐ethylene glycol‐b‐lactide) diacrylate. The hydrolysis of the copolyesters at pH 7.4 in a phosphate buffered saline solution at 37 °C was studied using ATR‐FTIR spectroscopy. It was found that the presence of the Boltorn, the PEG, and lactide block lengths both play vital roles in determining the structure‐property relationships in these materials. The ATR‐FTIR studies showed that with increasing lactide segment length, the rate of ester hydrolysis increased due to the increased concentration of the hydrolytically sensitive poly(lactic acid) (PLA) ester groups in the network. However, incorporation of Boltorn into the PLA‐PEG‐PLA copolymer did not significantly change the kinetic rate constant for hydrolysis of the PLA segments. The cytocompatibility of a typical one of these materials in the presence of its degradation by‐products was assessed using cultured osteoblasts from the rat. The hydrogel was degraded for 28 days and found to be cytocompatible with osteoblasts over days 23 to 28 of the hydrolysis period. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5163–5176     

Infra-red spectrum of water dimer in carbon tetrachloride solution

Geometries of six low-lying excited states of ozone are calculated by a limited SCF-CI procedure and are analysed in detail on the basis of the bonding properties of the molecular orbitals involved in the corresponding excitations. The triplet and singlet A ₂ states are sharply bent with a valence angle of 99°. Differences between triplet and singlet states of same spatial symmetry are also accounted for with special emphasis on the B ₂ states.     

Electron spin resonance detection of acrylic acid radical anions and related species in low temperature glasses

A contracted gaussian basis set in double-zeta form (plus polarization functions) has been used to calculate the vibrational characteristics of CH₃F by means of an ab-initio SCF finite-difference method. The diagonal force constants, with an error of about 10 per cent, are an upper limit to experiment. The off-diagonal interaction constants give a correct picture of the molecular force field, unlike the Hybrid Orbital Force Field model. With the derivatives of a dipole moment corresponding to a good theoretical evaluation (about 2D), it is possible to discuss the problem of signs in infra-red intensity analysis.