Novel methods for synthesizing halide-free alane without the formation of adducts

Many of the current synthesis methods for aluminum hydride (alane—AlH₃) involve reacting AlCl₃ and LiAlH₄ in solvents. The reaction requires the formation of an alane adduct such as AlH₃⋅[(C₂H₅)₂O] prior to obtaining crystallized stable α-AlH₃. This process requires several hours of pumping in a vacuum system to remove the ether and convert the alane etherate into stable α-alane. This crystallization process is both costly and hazardous because a large amount of highly flammable material (e.g. ether) is removed by vacuum pumps over several hours. Conversely, the work presented herein describes novel methods to synthesize adduct-free alane. It is demonstrated here that AlH₃ can form by mixing AlCl₃ and LiAlH₄ in the solid state and heating to 75^∘C; only α-AlH₃ was obtained. The α-AlH₃ product can be washed with minimal solvents leading to zero formation of alane adducts. In addition, the unwanted LiCl by-product is also removed during the solvent wash, resulting in halide-free α-alane. Although simply mixing and heating the reactants led to a 40% yield of alane, having the reactants compacted and mechanically pressed while heating increases the yield to 60% crystalline α-AlH₃.     

Accelerating the initial rate of hydrolysis of methyl parathion with laser excitation using monolayer protected 10 nm Au nanoparticles capped with a Cu(bpy) catalyst

Using a low power green laser, we have demonstrated a rate acceleration of ~2-fold for the hydrolysis of methyl parathion by irradiating the plasmon absorption band of Au nanoparticles capped with a Cu(bpy) catalyst.     

Limiting Distributions of Linear Programming Estimators

Smith (1994) proposes estimation in linear regression models with non-negative errors by maximizing the sum of fitted values subject to the constraint that the fitted values can be no larger than the corresponding response value. In this paper, we consider the limiting distribution of these estimators under very general conditions. Some extensions to local polynomial estimation are also considered.     

Comparing Classes of Finite Structures

We compare classes of structures using the notion of a computable embedding, which is a partial order on the classes of structures. Our attention is mainly, but not exclusively, focused on classes of finite structures. Also, a number of problems are formulated.     

Cleavage of MEM ethers by tetrahalozincate reagents

A modification of the zinc halide-mediated removal of the MEM group is described. By the expedient of adding two molar equivalents of etheral hydrogen chloride or of lithium halide, the method is extended to substrates which otherwise chelate the zinc reagent without undergoing deprotection. The compatibility of the resulting reagent systems with other functional groups is demonstrated, and examples are presented where deprotection of mono-MEM-protecteed 1,2- and 1,3-diols can be carried out, avoiding the cyclisation which occurs normally.