Hemiesters and hemiamides of maleic and succinic acid: synthesis and application of surfactants in emulsion polymerization with styrene and butyl acrylate

Hemiesters and hemiamides of maleic acid with different chain lengths of the hydrophobic alkyl group (R = C₈H₁₇, C₁₀H₂₁, C₁₂H₂₅, C₁₆H₃₃) have been synthesized and used as surfactants in the emulsion polymerization of styrene and butyl acrylate. The same polymerization experiments were also carried out using nonreactive surfactants with an analogous succinic structure. The chemical structure of the surfactants was confirmed by 1H nuclear magnetic resonance. The melting point and critical micelle concentration of the reactive surfactants described herein were measured. All of the surfactants studied provided good stability of styrene/butyl acrylate latexes, when compared with a reference latex of a styrene/butyl acrylate copolymer prepared with a surfactant sodium dodecyl sulfate. The amount of surfactant grafted onto the particles of the final latex was estimated by conductimetric titration. Between 33 and 68% of surfactant used in emulsion polymerization was found on the surface of latex particles. Electrolyte addition at high concentration and freeze/thaw cycle cause flocculation of latexes. Copyright © 1999 John Wiley & Sons, Ltd.     

Closed Shell Iron(IV) Oxo Complex with an Fe–O Triple Bond: Computational Design,Synthesis, and Reactivity

Iron(IV)-oxo intermediates in nature contain two unpaired electrons in the Fe–O antibonding orbitals, which are thought to contribute to their high reactivity. To challenge this hypothesis, we designed and synthesized closed-shell singlet iron(IV) oxo complex [(quinisox)Fe(O)]⁺ ( 1⁺ ; quinisox-H =(N-(2-(2-isoxazoline-3-yl)phenyl)quinoline-8-carboxamide). We identified the quinisox ligand by DFT computational screening out of over 450 candidates. After the ligand synthesis, we detected 1⁺ in the gas phase and confirmed its spin state by visible and infrared photodissociation spectroscopy (IRPD). The Fe–O stretching frequency in 1⁺ is 960.5 cm⁻¹, consistent with an Fe–O triple bond, which was also confirmed by multireference calculations. The unprecedented bond strength is accompanied by high gas-phase reactivity of 1⁺ in oxygen atom transfer (OAT) and in proton-coupled electron transfer reactions. This challenges the current view of the spin-state driven reactivity of the Fe–O complexes.     

Alkylation of the ambident indole ion in ionic liquids

Alkylation of the ambident indole anion in ionic liquids has been investigated. The reaction rate is greater in ionic liquids than in organic solvents. The polarity of certain ionic liquids has been determined to be located between methanol and acetonitrile. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 676–690. May, 2008.     

Particle simulation of Coulomb collisions: Comparing the methods of Takizuka & Abe and Nanbu

The interactions of charged particles in a plasma are governed by long-range Coulomb collision. We compare two widely used Monte Carlo models for Coulomb collisions. One was developed by Takizuka and Abe in 1977, the other was developed by Nanbu in 1997. We perform deterministic and statistical error analysis with respect to particle number and time step. The two models produce similar stochastic errors, but Nanbu’s model gives smaller time step errors. Error comparisons between these two methods are presented.     

Airline network revenue management by multistage stochastic programming

A multistage stochastic programming approach to airline network revenue management is presented. The objective is to determine seat protection levels for all itineraries, fare classes, points of sale of the airline network and all dcps of the booking horizon such that the expected revenue is maximized. While the passenger demand and cancelation rate processes are the stochastic inputs of the model, the stochastic protection level process represents its output and allows to control the booking process. The stochastic passenger demand and cancelation rate processes are approximated by a finite number of tree structured scenarios. The scenario tree is generated from historical data using a stability-based recursive scenario reduction scheme. Numerical results for a small hub-and-spoke network are reported. This research is supported by the DFG Research Center Matheon “Mathematics for key technologies” in Berlin.