Pyrazolylcyclotriphosphazene containing pendant polymers: synthesis,characterization, and phosphate ester hydrolysis using a Cu(II)-metalated cross-linked polymeric catalyst

A multi-pyrazolyl cyclotriphosphazene containing polymerizable group N(3)P(3)(3,5-Me(2)Pz)(5)(O-C(6)H(4)-p-C(6)H(4)-p-CH=CH(2)) (2) has been prepared from the corresponding chloro derivative N(3)P(3)Cl(5)(O-C(6)H(4)-p-C(6)H(4)-p-CH=CH(2)) (1). The X-ray structures of 1 and 2 have been determined. Compound 2 undergoes ready metalation with CuCl(2) to afford N(3)P(3)(3,5-Me(2)Pz)(5)(O-C(6)H(4)-p-C(6)H(4)-p-CH=CH(2)).CuCl(2) (3). Model compound N(3)P(3)(3,5-Me(2)Pz)(5)(O-C(6)H(4)-p-CHO).CuCl(2) (6) has been prepared and characterized by spectroscopy and X-ray crystallography. In this compound, the coordination around copper is distorted trigonal bipyramidal, and the cyclotriphosphazene coordinates in a non-gem N(3) mode. Compound 2 has been copolymerized with divinylbenzene to afford cross-linked multisite coordinating polymer CPPL which is readily metalated with CuCl(2) to afford copper-containing polymer CPPL-Cu. The coordination environment around copper in CPPL-Cu has been evaluated by obtaining its EPR, optical, and IR spectra and comparing them with those of model compounds 3 and 6. The utility of CPPL-Cu as a heterogeneous catalyst has been demonstrated in the phosphate ester hydrolysis involving three model phosphate esters: p-nitrophenyl phosphate (pNPP), bis(p-nitrophenyl) phosphate (bNPP), and 2-(hydroxypropyl)-p-nitrophenyl phosphate (hNPP). In all of these reactions, a significant rate enhancement of ester hydrolysis is observed. Detailed kinetic analyses to evaluate Michaelis-Menten parameters have also been carried out along with experiments to elucidate the effect of pH, solvent, and temperature on the rate of hydrolysis. Recycling experiments on the hydrolysis of pNPP with CPPL-Cu shows that it can be recycled several times over without affecting the rates.     

Solid-phase synthesis of isoxazolines

The polymer-supported synthesis of isoxazolines is described via nitrile oxide intermediates, starting from primary nitroalkanes in a one-pot process.     

Poly(ethylene glycol) (PEG) as a reusable solvent medium for organic synthesis. Application in the Heck reaction

[reaction: see text] PEG has been used as a solvent medium for regioselective Heck reactions with easy recyclability of solvent and Pd catalyst for the first time.     

Eckenprotoniertes cyclopropan in der gasphase: kopplung von unimolekularer [1.1]-H2-eliminierung aus C3H7+ und ringöffnung des cyclopropylkations

Based on energetic data (activation energy), kinetic isotope effects and MINDO/3 calculations it is suggested that unimolecular loss of H₂ from C₃H₇⁺ proceeds via a transition state (10) involving synchronous loss of a hydrogen molecule (symmetry allowed [1.1]-elimination) and ring opening of the cyclopropyl to the allyl cation. Alternative mechanisms are discussed.     

A biaxial nematic liquid crystal

We report a biaxial nematic liquid crystal in a simple thermotropic system.     

The optical rotatory dispersion of quartz

Many formulæ have been proposed to express numerically the rapid increase of the rotatory power of quartz with decrease of wavelength. An examination of these formulæ shows that they are wholly inappropriate for the case of quartz. It has been shown that the entire range of data from the visible to the extreme ultraviolet is accurately represented by a new type of formula involving only two constants,viz.,

$$\rho = \frac{{k\lambda ^2 }}{{(\lambda ^2 - \lambda _0 ^2 )^2 }},$$     

Infrared spectra of the superionic conductors Na,K, Rb,Ag and Ti β-aluminates

A detailed analysis of the infrared reflectivity spectra of the superionic conductors X β-aluminates (X = Na, K, Ag, Rb and Tl) is presented. A Kramers-Kronig analysis and the oscillator fits to the data have yielded the frequencies of the transverse optic and associated longitudinal optic modes. A model which ignores the coupling between the spinel blocks accounts for the number of observed infrared modes as well as the Raman modes. It is shown that even for the modes characteristic of the motions of the disordered X-ions, the wave vector selection rule is still valid. The results are discussed with the available theoretical calculations.     

Phonons in titanium doped vitreous silica

In this paper we report the infrared and Raman studies of titanium doped silicate glasses for a number of Ti concentrations. New modes associated with the titanium groups are identified. The observed shifts and broadenings in the spectra of vitreous silica are discussed in the context of random network models. The “anomalous” decrease in density with the addition of titanium is attributed to an increase in the average intertetrahedral angle of the SiO₄ network.