NMR-spektroskopische Untersuchungen an 15N-markierten Phenylamidochlorocyclotetraphosphazenen

NMR Spectroscopic Studies of ¹⁵N Labelled Phenylamidochlorocyclotetraphosphazenes Some endocyclically ¹⁵N labelled phenylamidochlorocyclotetraphosphazenes, ¹⁵N₄P₄Cl₇NHPh, 6,8-¹⁵N₄P₄Cl₆(NHPh)₂ and 4,8-¹⁵N₄P₄Cl₆(NHPh)₂, as well as the corresponding exocyclically ¹⁵N labelled compounds N₄P₄Cl₇¹⁵NHPh, 6,8-N₄P₄Cl₆(¹⁵NHPh)₂ and 4,8-N₄P₄Cl₆(¹⁵NHPh)₂ were prepared, and the ³¹P and ¹⁵N NMR spectra were recorded. In the case of the endocyclically labelled compounds it is possible to determine the relative signs of the coupling constants ¹J_PN by means of spectra simulation. In order to interprete the relatively large coupling constants ³J_PN to the exocyclic nitrogen a Karplus diagram was calculated and discussed.     

NMR-spektroskopische Untersuchungen an Mercaptophosphazenen. I. Verlauf der Reaktion von Natriumethylmercaptid mit Hexachlorocyclotriphosphazatrien bzw. Octachlorocyclotetraphosphazatetraen

N.M.R. Spectroscopic Investigations of Thiophosphazenes. I. Reactions of Sodium Ethylthiolate with Hexachlorocyclotriphosphazatriene and Octachlorocyclotetraphosphazatetraene By reactions of hexachlorocyclotriphosphazatriene with an excess of sodium ethylthiolate as a suspension in ether all of the possible geminal derivatives N₃P₃Cl_6?n(SEt)_n; n = 1–6, are formed in different quantities. Products from reactions of octachlorocyclotetraphosphazatetraene with sodium ethylthiolate, N₄P₄Cl_8?n(SEt)_n, likewise contain all of the geminally substituted derivatives up to n = 8 with the exception of the derivatives with n = 1 and n = 7. Compounds with n = 3, 4, or 5 exist in two geminal isomers respectively. Nongeminal ethylthiochlorophosphazenes were not found by any reaction. The formed compounds were isolated by chromatographic methods and studied by ³¹P n.m.r. spectroscopy.     

Some thermodynamic quantities of n-alkanes as a function of chain length

Summary Results from high pressure dilatometry onn-alkanes and linear polyethylene and literature data yield a linear relation between specific volume, entropy and enthalpy of fusion, the reciprocal melting temperature and 1/n, wheren denotes the number of C-atoms per molecule. Extrapolating towards infiniten one always obtains polyethylene data.The differences in the properties ofn-alkanes and polyethylene can be ascribed to the influence of the chain ends. Assuming entropy and enthalpy contributions from these chain ends as made probable by a molecular model one can quantitatively explain then-dependence of the above mentioned quantities including their pressure dependence.With 10 figures and 2 tables     

Nachweis und Bestimmung von Zuckerarten

Ohne Zusammenfassung     

Small-angle X-ray scattering study of a poly(oxyphenylethylene)–poly(oxyethylene) diblock copolymer gel under shear flow

 The structure and flow behaviour of a micellar “cubic” phase is studied, using small-angle X-ray scattering (SAXS) and constant stress rheometry on a poly(oxyphenylethylene)–poly(oxyethylene) diblock copolymer in water. The predominant structure is a face-centred cubic (fcc) array of spherical micelles, which under shear undergoes layer sliding to give a scattering pattern from stacked hexagonal close-packed layers. A detailed analysis of the SAXS data indicates the presence of a fraction of grains with a structure distorted from a fcc phase. The additional reflections that characterize this structure can be indexed to a rhombohedral unit cell, space group R3ˉm, with the same volume as the fcc unit cell. The rhombohedral unit cell corresponds to a cubic cell that has been “stretched” along a [111] direction, and it is suggested that such a structure results from the gradient in shear velocity in the Couette cell employed. Shearing at high shear rates leads to a “smearing out” of the reflections, but upon cessation of shear under these conditions a highly oriented SAXS pattern is obtained, which confirms the persistence of rhombohedral ordering. The shear-induced changes in orientation are correlated to a plateau observed in the stress plotted against shear rate, such a plateau being a sign of inhomogeneous flow. Received: 8 September 2000 Accepted: 29 November 2000