摘要:

AbstractThe reactions of chlorine and fluorine atoms with the structural isomers CH3CHO and C2H4O have been studied at low pressures and room temperature by the discharge flow technique with mass spectrometric detection. Using the reference reactionsthe relative rate constant for the reactionswere determined:k1/k0= 1.04 ± 0.09,k2/k0= 0.49 ± 0.04,k3/k00= 0.47 ± 0.05. — Reaction (1) proceeds mainly via hydrogen abstraction from the aldehyde group (>93%) forming CH3CO. In the reactions of ethylene oxide (2), (3) the abstraction route is observed, contributions from addition channels in reaction (2) are discu

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930403

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1989

数据来源: WILEY

摘要:

AbstractVibrationally highly excited azulene (E≤ 17000 cm‐1) was prepared by light absorption in the S1band and subsequent fast internal conversion. Collisional energy transfer in 22 bath gases was measured in the temperature range 300–800 K. In the investigated energy range, the average energies 〈ΔE〉 transferred per collision nearly linearly depend on the excitat

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930404

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1989

数据来源: WILEY

摘要:

AbstractThe formation of dimers and oligomers of the monomeric sodium halides NaCl, NaBr and NaI were studied in a flow reactor at a pressure of 300 Pa and temperatures of 623 and 645 K. The reactions propynyl chloride/bromide + Na vapour were used to generate the gaseous NaCl and NaBr while the sodium iodide monomer was formed via the reaction Na + CH3I. The rate constants for the dimerizations of NaCl, NaBr and NaI were found to be 8.0 · 1013, 5.0 · 1013and 5.0 · 1012cm3mol‐1s‐1, respectively. Under the experimental conditions the dimerizations were near their high‐pressure limits. NaCl oligomers up to [NaCl]5were detected while the detection of NaBr oligomers was limited by the accessible mass range to [NaBr]3. — In the system Na + Phenyliodide (PhI) mixed Na/Phenyliodides were formed but hardly any NaI. Disodium‐phenyliodide was a main product. Higher compounds such as Na3Ph2J and Na3PhI2were also detected in lower concentrations. In addition, diphenyl was a product of a homogeneous reaction while benzene was formed both by a heterogeneous and a homogeneous reaction. The reaction mechanism is discussed on the basis of an intermediate complex Na +

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930405

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1989

数据来源: WILEY

摘要:

AbstractCrystal structures of the stable and a metastable phases of 2,4‐bis(trichloromethyl)‐benzo‐1,3‐dioxine‐6‐carboxylic acid (TMB‐COOH) and 2,4‐bis(trichloromethyl)‐benzo‐1,3‐dioxine‐6‐amine (TMB‐NH2) were determined at room temperature. Crystal data are as follows; TMB‐COOH (stable): monoclinic, space group C52h‐P21/n,a= (1052.6 ± 0.2) pm,b= (2582.2 ± 0.4) pm,c= 598.7 ± 0.3) pm,β= 99.86° ± 0.02°,R= 0.053; TMB‐COOH (metastable): monoclinic,space group C52h‐P21/c,a= (577.5 ± 0.5) pm,b= (2087.2 ± 1.1) pm,c= (1318.6 ± 0.7) pm,β= 91.98° ± 0.06°,R= 0.098; TMB‐NH2: orthorhombic, space group C92v‐Pna21,a= (2539.0 ± 0.2) pm,b= (1005.1 ± 0.1) pm,c= (566.7 ± 0.1) pm,R= 0.049. Disorder of hydrogen atom in the OH ··· O hydrogen bond system was found for the cyclic dimers of TMB‐COOH in both phases. Judging from the molecular structures determined, chloral hydrate and 4‐substituted phenols seem to react in a stereospecific way to give a single conformer found in these crystals. The35Cl NQR spectra of TMB‐COOH, TMB‐NH2and related compounds were measured in the range 77 ≦ T/K ≦ 400. The temperature dependence of the NQR spectra showed that the potential barrier hindering the reorientation of the group is considerably different for the two nonequivalent CCl3groups in a molecule. Atom‐atom potential calculations based on the crystal data showed that the difference is of intermolecular nature. The NQR frequencies calculated from the orbital popula

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930406

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1989

数据来源: WILEY

摘要:

AbstractThe temperature dependence studies of1H and19F NMR spin‐lattice relaxation times (T1) as well as differential thermal analysis measurements were carried out for [(CH3)4N]SbF6crystals. A phase transition assignable to the second order one was located at 200 K, above which temperature the temperature gradient of1HT1and19FT1curves became slightly gentler. The appearance of the1HT1curve was BPP like one although a maximum was detected at ca. 110 K. The1HT1minimum was explained as resulting from the CH3C3reorientation and the overall reorientation of the cation activated at almost the same temperature. The19FT1curves observed at 19.5 and 32 MHz were somewhat complicated. On the high temperature region above ca. 120 K,19FT1was determined mainly by the motion of the cation activated at higher temperatures than that of the anion through1H‐19F magnetic dipolar interactions. On the other hand,19FT1observed below 120 K have a broad minimum attributable to the overall reorientation of the complex anion. The motional parameters for the above motions were derived. On the analysis of theT1curves observed, cross relaxation mechanism operative between1H and19F nuclei is fully conside

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930407

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1989

数据来源: WILEY

摘要:

AbstractThe35CI NQR spectra of pentachloroethylstannate(IV) complex salts A2[(C2H5)SnCl5)] with four different cations A⊕(A⊕= Tetra‐ methylamnionium, [(CH3)4N]⊕(I), Pyridinium, [CSHSNH]⊕(II). Methylammonium, [CH3NH3]⊕ (III), and 4‐Picolinium, [4‐CH3‐ C5H4NH]⊕ (IV)) have been recorded and their crystal structures were determined. The compounds crystallize with a distorted K2PtCI6‐type structure ((I): space group C62h/c, a = 1408.9 pm, b = 1123.2 pm, c = 1332.7 pm, β = 90.94°, Z = 4; (II): space group C52h/c, a = 1618.8 pm, b = 744.6 pm, c = 1520.0 pm, β = 90.515°, Z = 4; (IV): space group Ct‐Pi, a = 1093.4 pm, b = 938.8 pm, c = 722.6 pm, α = 108.37°, β = 90.84', γ = 93.90, Z = 2 = (IV): space group D42‐P212121, a = 2181.1 pm, b = 1088.3 pm, c = 858.2 pm, Z = 4). The effects of the substitution of one Cl⊖ligand within a SnCl2⊖6octahedron by the stronger electron donor C2H⊖5are: (a) The mean strength of all 5 Sn—Cl bonds is lowered. This is reflected by a decrease of the mean35Cl NQR frequencies and an increase in Sn—Cl bond length compared with hexachlorostannates; (b) There exists a distinct cis and trans influence of the ethyl group. The Sn—Cl bonds in cis position to the ethyl group are highly weakened (cis‐weakening), while the trans effect is much smaller in magnitude and probably of opposite sign (trans‐strengthening). The influence of hydrogen bonds weakens Sn—Cl bonds in addition to cis‐weakening. A correlation of35Cl NQR frequencies and Sn—Cl bond lengths shows a slope of —0.6 MHz/pm. The ethyl group is ordered in (II) and (III), disordered in (IV) and rotates in (I). In (I) a phase transition at 180 K could be detected by35Cl NQR and DTA, the reason

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930408

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1989

数据来源: WILEY

摘要:

AbstractThe liquid crystalline smectic mixed phases in eight binary systems have been investigated by X‐ray methods. The mixed phases have orthogonal (sE, sB, sA‐phases) or tilted (sG, sF, s1‐phases) structures. Especially the thickness of the smectic layersdas a function of the concentration has been considered. In the orthogonal phases the functiond(x)is related to an averaged molecular lengthT(x)=xAlA+xBlB, wherelAandlBdenote the molecular lengths of the compounds A and B in the most stretched all‐trans‐configuration. In the tilted phases besidesT(x)the tilt angleβ(x)is related tod(x).Adding the second compound the tilted molecular long axes arise within

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930409

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1989

数据来源: WILEY

摘要:

AbstractX‐ray studies on microdomains of liquid crystals with higher ordered smectic phases require a technique providing a relative high resolution of the X‐ray reflexes. A diffractometer technique for such X‐ray investigations on liquid crystals and also a special oven, containing permanent magnets for getting aligned microdomains, is described. Some examples for the application of this technique on bulk samples and free standing films are disc

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930410

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1989

数据来源: WILEY

摘要:

AbstractFIR‐absorption spectra of methyl fluoride (CH3F) as a pure fluid and as a one mole percent component in mixtures with dense argon and CF4have been measured. A frequency range between 10 cm‐1and 200 cm‐1was covered. Temperatures of —10, 69 and 125°C were used. Total sample pressures extended to 1000 bar.PVT‐data permit the discussion of the spectra as functions of density. Measurements were made with a modified Fourier‐transform IR‐spectrometer. An optical absorption cell for use to 1000 bar and 200°C is described. The molar absorptivity at 69°C has a pronounced maximum at 40 cm‐1at all temperatures and densities which indicates hindered rotation. This absorption decreases with growing density and an increasing absorption develops above 70 cm‐1, caused by in termolecular libration. The suppression of the CH3F‐rotation in the dense argon is much weaker than in the pure polar fluid. The intermolecular mean squared torque increases linearly with density with the pure fluids CH3F and CHFl2F and about four times as strongly as with the compounds diluted in argon. Spectral fourth moments of the power spectra and time correlation functions for pure fluids and mixtures are compared to show the influence of dipole interaction on rotation and libration. Spectra obtained with CH3F in high pressure CF4are analogous to those

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930411

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1989

数据来源: WILEY

摘要:

AbstractThe decomposition of hydrogen peroxide in the presence of potassium iodate and sulphuric acid (the Bray‐Liebhafsky oscillatory reaction) is analysed at different temperatures. It is noted that the temperature variation at constant acidity have the similar effect on the system as the acidity variation at constant temperature. Thus, the character of oscillations can be changed by temperature variation; the system thereby shifts to some other kinetic state in which the resumption of the oscillatory trains, in the region of the smooth catalysis after completion of the last regular oscillation, can be provoked by dilution. In spite of this, the activation energy of the overall reaction is calculate

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930412

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1989

数据来源: WILEY