Synthesis of alpha-fluorosulfonamides by electrophilic fluorination

Alpha-fluorosulfonamides were prepared by electrophilic fluorination of tertiary sulfonamides using N-fluorobenzenesulfonimide as fluorinating agent and utilizing the dimethoxybenzyl group (DMB) as a new sulfonamide protecting group. Removal of the DMB group with TFA/CH(2)Cl(2) gave primary and secondary alpha-fluorosulfonamides.     

Parallel interconnection and neural network systems employing semiconductor array technology and computer-generated holography

An experimental 16-channel parallel interconnection system able to support 100 Mbits^–1 per channel and an opto-electronic neural network operating at up to 50 Mbits^–1 have been constructed to demonstrate the potential of optics in processing systems. Both experiments operate at a wavelength of 1.5m. Components developed for these systems include arrays of InGaAs/InP MQW surface modulators for low-power electrical-to-optical conversion; InGaAs/InP for detector arrays, which are hybrid integrated with GaAs amplifier arrays; and computer-generated holograms for efficient beam splitting and to encode weights in the optical beam intensities. Each of these demonstrations has considerable scope for increasing the degree of parallelism and the operating speed. Recent modifications to the neural network enable the weights to be varied and training has been demonstrated with a novel algorithm that uses the high operating speed to advantage.     

Oscillations and chaos in CO+O(2) combustion

The gas-phase reaction between carbon monoxide and oxygen (in the presence of small amounts of hydrogen) shows bistability and oscillatory behavior. Typically, the oscillatory ignition has a period-1 relaxation waveform. The limit cycle is born at a saddle-node loop and terminates via a supercritical Hopf bifurcation. For a mean residence time of 8 s there is a period-doubling to a period-2 solution followed by period-halving to quasisinusoidal period-1 oscillations. At longer residence times, more period-doublings forming a full cascade to chaos with subsequent periodic windows are observed. The chaotic attractor has an underlying single-humped next maximum map.     

Organo-tricyanoborates as tectons: illustrative coordination polymers based on copper(I) derivatives

The first systematic study on the use of tricyanoborates as ligands is presented. The tricyanoborates [RB(CN)3]- (R = oct and Ph) can be prepared by direct cyanation of RBCl2 precursors as well as by thermolysis of the corresponding isocyanides [RB(NC)3]-. The first organo-cyanogallates [RGa(CN)3]- (R = Bu, C6H2-2,4,6-Me3) were prepared from the corresponding dichloride, the structure of Et4N[mesGa(CN3] being confirmed crystallographically. The reaction of equimolar [RB(CN)3]- (R = oct, Ph) and [Cu(MeCN)4]+ afforded two-dimensional polymers [RB(CN)3Cu(NCMe)]. The sheets arise via conjoined hexagonal B3Cu3(CN)6 rings with chair conformations. The reaction of excess [PhB(CN)3]- and [Cu(MeCN)4]+ gives the polymer [K(18-crown-6)]{Cu[PhB(CN)3]2}. Treatment of [PhB(CN)3]- with [Cu(PCy3)2(NCMe)x]PF6 gave the one-dimensional polymer [PhB(CN)3Cu(PCy3)2], wherein two of the three BCN substituents are coordinated.     

Application of ionic liquids as low-volatility plasticizers for PMMA

Room temperature ionic liquids (ILs) based on imidazolium salts, were found to be excellent plasticizers for poly(methyl methacrylate), with improved thermal stability, and the ability to reduce glass transition temperatures to near 0 °C. Because ILs have environmentally benign properties, they can be used in place of traditional chemicals in numerous products and processes. In this work, PMMA was formulated using dioctyl phthalate, DOP, as a traditional plasticizer, and properties were compared to PMMA plasticized with two ILs: butyl methylimidazolium/hexafluorophosphate, [bmim⁺][PF₆⁻], and hexyl methylimidazolium/hexafluorophosphate, [hmim⁺][PF₆⁻]. Formulations incorporated up to 30 vol.% DOP and 50 vol.% ILs. Bulk and plasticized polymers were characterized for glass transition temperature, elastic modulus, and the thermal stability of the plasticizers.