Phase equilibria and excess properties for binary systems in reactive distillation processes Part I. Methyl acetate synthesis

Isothermal vapor–liquid equilibrium (VLE) and excess enthalpy (H^E) data were measured for binary systems required for the design of reactive distillation processes for the methyl acetate production. The isothermal P–x data were measured with the help of a computer-operated static apparatus. A commercial isothermal flow calorimeter was used for the determination of the heats of mixing. Temperature-dependent interaction parameters for the UNIQUAC model were fitted simultaneously to the experimental data from this work and other authors.     

Synthesis and Polymerization of Carbamate-Linked Cyclodextrin Methacrylate Monomers

Abstract

A one-step synthesis for cyclodextrin methacrylate monomers was examined starting from α-, β- and γ-cyclodextrin. The reaction of 2-isocyanatoethyl methacrylate as well as allylisocyanate with the corresponding cyclodextrin gave the monofunctionalized carbamate-linked cyclodextrin methacrylates 2, 6 and 9 and allylcarbamates 11 and 14 in moderate yields. By NMR spectroscopic means, it could be proven that in all cases only the primary 6-hydroxyl groups of the cyclodextrins reacted with the isocyanate group. For the synthesis of a β-cyclodextrin monoallyl compound, a substitution reaction of purchasable 6-O-monotoluenesulfonyl-β-cyclodextrin with allylamine gave 6-N-allylamino-6-deoxy-β-cyclodextrin 18 in high yield. The reaction of 2-isocyanatoethyl methacrylate with α-cyclodextrin to the 6-O-carbamoyl-2-methylpropenoylethyl-α-cyclodextrin (2) was optimized so that the monomer 2 could be prepared on a larger scale without chromatographic separation. The aqueous radical homopolymerization of 2 with the peroxodisulfate/bisulfite redox initiator gave the water soluble cyclodextrin polymer 19 in good yield. Its molecular weight was determined by gel permeation chromatography to be M_n = 101,800 corresponding to an average degree of polymerization P_n = 90.     

Coherence-based axial point-spread function engineering for two-photon excited polymerization

We show in proof-of-principle experiments an axial resolution improvement in two-photon-excited fluorescence and polymerization enabled by the short coherence length of two counter-propagating ultrashort laser pulses. The interference of these pulses generate a spatial interference fringe pattern, whose width scales inversely to the spectral bandwidth and is therefore considerably shorter than the effective focal length of a laser beam conventionally focused from only one side.     

On the design of Dammann gratings

In recent years the design of Dammann gratings for the application as array illuminators has been widely discussed. Important progress has been made. However, some problems concerning the control of design algorithms remain to be solved. It is shown how design theory of diffractive elements can be used to avoid these difficulties and to formulate a straightforward design method to obtain Dammann gratings optimized in diffraction efficiency and uniformity.     

Neue Aminometallane des Aluminiums und Galliums

New Aminometalanes of Aluminum and Gallium The reaction of secondary amines R′RNH with trimethyaluminum leads to the formation of dimeric aminoalanes [RR′NAlMe₂]₂ ( 1 ) (R = 2,6-Me₂C₆H₃, R′ = SiMe₂(2,4,6-Me₃C₆H₂)) and 2 (R = Ph, R′ = SiMe₃). Using a different stoichiometric ratio, a monomeric aminoalane [RR′N]₂AlMe ( 3 ) (R = Ph, R′ = SiPh₂Me) is obtained, having an aluminum atom of coordination number three due to the steric demand of the substituents. The synthesis of the corresponding aminogallanes 4 , 5 and 6 is achieved by reaction of lithium amides LiNRR′ (R = Ph, 2,6-iPr₂C₆H₃; R′ = SiMe₃, SiMe₂iPr) with dimethylgalliumchloride, Me₂GaCl, in n-hexane. The formation of the dimeric species is in 1 through carbon while that in 2 and 3 is formed through nitrogen. The X-ray single crystal structure analysis of 1 , 2 , 3 and 4 are reported.     

A Novel Concept for Combinatorial Chemistry in Solution: Synthesis of Highly Substituted Pyrrolidines by Multicomponent Domino Reactions

The multicomponent domino Knoevenagel hetero‐Diels? Alder hydrogenation process of N‐[(benzyloxy)carbonyl(Cbz)‐protected amino aldehydes with N,N‐dimethylbarbituric acid and the trimethylsilyl enol ethers 1 – 3 leads to the formation of the substituted pyrrolidines 12 – 15 . Under the same conditions, reaction of the trimethylsilyl enol ether 4 , obtained from acetophenone, gave the primary amines 18a , b probably due to a hydrogenolytic cleavage of the intermediately formed pyrrolidines. The zwitterionic products were obtained in high purity simply by precipitation with Et₂O.