Aryl Boronic Acid Catalysed Dehydrative Substitution of Benzylic Alcohols for C−O Bond Formation

A combination of pentafluorophenylboronic acid and oxalic acid catalyses the dehydrative substitution of benzylic alcohols with a second alcohol to form new C−O bonds. This method has been applied to the intermolecular substitution of benzylic alcohols to form symmetrical ethers, intramolecular cyclisations of diols to form aryl-substituted tetrahydrofuran and tetrahydropyran derivatives, and intermolecular crossed-etherification reactions between two different alcohols. Mechanistic control experiments have identified a potential catalytic intermediate formed between the aryl boronic acid and oxalic acid.     

Gas adsorption in mcm-41 porous silicas dynamic measurements using sans

The European Physical Journal E - The isothermal gas adsorption of two hexane isomers (n-hexane and cyclohexane) in the mesopores of MCM-41 silica have been investigated by small angle neutron...     

The effect of solvent upon molecularly thin rotaxane film formation

We have investigated variations in molecularly thin rotaxane films deposited by solvent evaporation, using atomic force microscopy (AFM). Small changes in rotaxane structure result in significant differences in film morphology. The addition of exo-pyridyl moietes to the rotaxane macrocycle results in uniform domains having orientations corresponding to the underlying substrate lattice, while a larger, less symmetric molecule results in a greater lattice mismatch and smaller domain sizes. We have measured differences in film heights both as a function of the solvent of deposition and as a function of surface coverage of rotaxanes. Based on these observations we describe how the use of solvents with higher hydrogen-bond basicity results in films which are more likely to favour sub-molecular motion.     

Molecular constants for the ã 3A2 state of formaldehyde

The 0⁺–0 and 1⁺–0 bands of the ā ³A₂X? ¹A₁ transition of formaldehyde have been reinvestigated using higher resolving power than was available in the earlier work of Raynes. The rotational analyses have been considerably extended, and improved molecular constants for the ā ³A₂ state have been obtained with the aid of a new triplet—singlet computer programme.^sSR branches of the K′ = 7K″ = 5 and K′ = 5K″ = 3 subbands have been observed in the 0⁺–0 band using 7m atm of absorbing gas. These results provide the first example of the observation of ΔK = ±2 transitions in triplet—singlet bands of a polyatomic molecule. The “perpendicular” transition moment is found to be about 10% of the “parallel” transition moment.     

Microwave—optical double resonance in the A1A2 excited state of thioformaldehyde

Microwave—optical double resonance experiments have been carried out on the 4_o¹ band of the $\text{A}$¹A₂$\text{X}$¹A₁ system of thioformaldehyde (H₂CS). More than 100 microwave and radiofrequency transitions have been observed in the $\text{A}$¹A₂ excited state. Many of these transitions are magnetically sensitive. Some of the excited state levels are perturbed by triplet levels and others by high vibrational levels of the ground state.     

The interference of heteronuclear chromium(III) tartrate complexes in the EDTA titration of cobalt(II), copper(II), zinc(II) and cadmium(II)

When present together in solution, chromium(III) and tartrate can interfere seriously in the titration of Co(II), Cu(II), Zn(II) and Cd(II) with EDTA. Ternary (heteronuclear) tartrate complexes containing Cr(III) and bivalent metal ion in the ratio 1:1 are formed. The conditions for the formation of these complexes have been investigated. Cadmium(II) can be determined without interference by employing potentiometric end-point detection.     

Sol-Gel Routes to Zeolite Membranes and Thin Films

The synthesis of zeolite membranes and thin films using the secondary growth process is briefly described. In this process colloidal zeolite particles (sols) are prepared hydrothermally and then subsequently deposited on substrates to produce uniform layers of controlled thickness, as illustrated with silicalite and zeolite-A. The formation and growth of the zeolite sols has been investigated in situ by small angle neutron scattering (SANS). SANS measurements on silicalite sols at progressively higher concentrations have provided details of the colloid interactions which lead to zeolite gel-layer structures which are uniform and free of defects.     

An experiment to test an explanation of a possible violation of quantum theory

An experiment to test a possible explanation of the Schmidt backwards causation results is suggested. The experiment might distinguish between many- and one- world interpretations of quantum theory.