Copolymerization at high conversion when the concentration of one monomer does not change

Exact equations and several computer programs were developed for use in studies on copolymerizations carried to high conversion when the concentration of one of the monomers (A) remains constant. Simple ACSL® and DESIRE® programs are described for simulating such copolymerizations, and their output was used to test programs and procedures that were developed to evaluate monomer reactivity ratios for such copolymerization systems. Based on an integrated form of the copolymer equation, Excel® and Fortran programs were developed for evaluating monomer reactivity ratios from information about initial monomer compositions, copolymer compositions, and the fractions of the second monomer (B) that reacted. A graphical procedure for evaluating monomer reactivity ratios from such data was also developed. A previous program developed for calculating information about monomer sequence distributions in copolymers was modified so that it would apply to copolymerization at high conversion when the concentration of one monomer remains constant. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1118–1128, 2000     

High-speed ESPI and related techniques: overview and its application in the automotive industry

This paper provides an overview of recent developments and applications of high-speed electronic speckle pattern interferometry (ESPI) and related techniques ranging from high-speed pulsed laser techniques to high-speed camera methods. Different methods for extracting the phase distribution from high-speed ESPI fringe patterns are compared. Unique applications in the automotive industry using these techniques are provided. Finally, the outlook for high-speed ESPI and high-speed digital holographic interferometry are discussed.     

Difluorinated analogues of shikimic acid

Investigations into the quinate to shikimate transformation have been carried out, the results of which have been exploited in the synthesis of a novel difluoromethylene homologue of shikimic acid from (−)-quinic acid. Martin's sulfurane {Ph₂S[OC(CF₃)₂Ph]₂} was the reagent of choice for the key dehydration step of this synthesis. The results of investigations into the synthesis of the important natural product analogue, 6,6-difluoroshikimic acid are also reported.     

Synthesis of highly substituted pyrrolidines via palladium-catalyzed cyclization of 5-vinyloxazolidinones and activated alkenes

N-Tosyl-5,5-divinyloxazolidin-2-one undergoes a palladium-catalyzed decarboxylative cyclization across a range of electrophilic alkenes to give the corresponding pyrrolidine derivatives bearing two contiguous quaternary centres. Alkenes bearing two electron-withdrawing groups are required; pyrrolidines were not formed from mono-activated alkenes. Bulky, electron-rich phosphines promote pyrrolidine formation with less highly electrophilic, doubly activated alkenes, and a dramatic improvement is observed in the presence of iodide.     

A quick diagnostic test for NMR receiver gain compression

Modern NMR spectrometers require receivers to work within their linear ranges to maintain high fidelity line shape and peak integration. For better sensitivity, the receiver gain has to be optimized to detect dilute analytes; however, gain compression needs to be avoided. Here, we explore if and how linear receiver performance can be achieved for a couple of representative gain settings on a spectrometer. In the case of slight receiver gain compression, not only will the peak integral be attenuated but a very small line‐shape change can also be observed. Hence, we can resort to resonance integration and line‐shape analysis for gain compression diagnosis. As such, NMR signals, regardless of their observed amplitude difference in frequency domain, can be accurately compared in quantitative analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

Convenient Syntheses of Perdeuterioacrylonitrile and β,β-Dideuterioacrylonitrile

Perdeuterioacrylonitrile can be prepared conveniently from succinonitrile in a two-step process. Succinonitrile is exchanged with D₂O to obtain perdeuteriosuccinonitrile, which is then pyrolyzed at ～550°C to obtain perdeuterioacrylonitrile and DCN. CDBCN and CzDsCN are by-products of this reaction. A chemical procedure for separating perdeuterioacrylonitrile from these materials was developed. This involved formation of the Diels-Alder adduct of cyclopentadiene with perdeuterioacrylonitrile, followed by pyrolysis of the purified adduct at -330°C. Cyclopentadiene was removed from the resulting pyrolyzate by reaction with maleic anhydride. Purified perdeuterioacrylonitrile exchanged with H₂O to yield β,β-dideuterioacrylonitrile in good yield and good isotopic purity.