Stabilization of the Closed-Ring Isomer of Spiropyran by Amide Naphthotube in Water and Its Application in Naked-Eye Detection of Toxic Paraoxon

The thermodynamically unstable, colourless closed-ring isomer of spiropyran can be stabilized in water by the anti-configurational isomer of amide naphthotube. The influence of the binding on the thermodynamics and kinetics of spiropyran have been studied. The complex was further used to prepare a test paper that allows naked-eye detection of toxic paraoxon.     

Computation of hydration free energies using a parameterized continuum model: Study of equilibrium geometries and reactive processes in water solution

A parameterized self-consistent reaction field model allowing computation of the total free energy of hydration of organic molecules at the ab initio level is presented. The approach uses electrostatic plus polarization energies calculated with the help of a continuum model. The remaining solvation free energy terms are obtained by a simple formula based on atomic parameters and atomic accessible surface areas (ASAs), which are determined with the ASA analytical algorithm. Analytical derivatives of the atomic surfaces areas have been implemented. The atomic parameters have been obtained by a linear regression fit of the calculated and experimental free energies of solution in water for a set of 35 molecules, leading to a standard deviation of 0.75 kcal/mol. Effects of nonelectrostatic terms on solute geometries, association energies, and activation barriers are illustrated. © 1996 by John Wiley & Sons, Inc.     

Rate constants for the gas-phase reaction of ozone with 1, 1-disubstituted alkenes

The gas-phase reaction of ozone with eight alkenes including six 1,1-disubstituted alkenes has been investigated at ambient T (285–298 K) and p = 1 atm. of air. The reaction rate constants are, in units of 10⁻¹⁸ cm³ molecule⁻¹ s⁻¹, 9.50 ± 1.23 for 3-methyl-1-butane, 13.1. ± 1.8 for 2-methyl-1-pentene, 11.3 ± 3.2 for 2-methyl-1,3-butadiene (isoprene), 7.75 ± 1.08 for 2,3,3-trimethyl-1-butene, 3.02 ± 0.52 for 3-methyl-2-isopropyl-1-butene, 3.98 ± 0.43 for 3,4-diethyl-2-hexene, 1.39 ± 17 for 2,4,4-trimethyl-2-pentene, and >370 for (cis + trans)-3,4-dimethyl-3-hexene. For isoprene, results from this study and earlier literature data are consistent with: k (cm³ molecule⁻¹ s⁻¹) = 5.59 (+ 3.51, &minus 2.16) × 10⁻¹⁵ e^{(−3606±279/RT)}, n = 28, and R = 0.930. The reactivity of the other alkenes, six of which have not been studied before, is discussed in terms of alkyl substituent inductive and steric effects. For alkenes (except 1,1-disubstituted alkenes) that bear H, CH₃, and C₂H₅ substituents, reactivity towards ozone is related to the alkene ionization potential: In k<(10⁻¹⁸ cm³ molecule⁻¹ s⁻¹) = (32.89 ± 1.84) − (3.09 ± 0.20) IP (eV), n = 12, and R = 0.979. This relationship overpredicts the reactivity of C_≥3 1-alkenes, of 1,1-disubstituted alkenes, and of alkenes with bulky substituents, for which reactivity towards ozone is lower due to substituent steric effects. The atmospheric persistence of the alkenes studied is briefly discussed. © 1996 John Wiley & Sons, Inc.     

Studies on pyrrolidones. Reactivity of β-enaminoesters derived from pyroglutamic acid. Synthesis of methyl cyano[l-methyl-5-(5-methyl[1,3,4]oxadiazol-2-yl)pyrrolidin-2-ylidene]acetate

The 5-methoxycarbonyl group of β-enaminoesters derived from methyl pyroglutamate was transformed into acids, amides and 1,3,4-oxadiazole.     

Characterization of the Microhardness of Ion-implanted GaP

Implantation induced changes of the microhardness are studied in GaP single crystals which were bombarded with ions in the range of mass numbers M = 1–40. It is observed that point defects and incorporated hydrogen have a stronger hardening effect. The effect of defect complexes is lower, and amorphized layers are softer than crystalline layers.     

Enantioselective crossed intramolecular [2+2] photocycloaddition reactions mediated by a chiral chelating Lewis acid

In intramolecular [2+2] photocycloaddition reactions, the two tethered olefins can approach each other in a straight or in a crossed fashion. Despite the fact that the latter reaction mode leads to intriguing, otherwise inaccessible bridged skeletons, there has so far not been any enantioselective variants thereof. This study concerned the crossed [2+2]-photocycloaddition of 2-(alkenyloxy)cyclohex-2-enones to bridged cyclobutanes. It was found that the reaction could be performed with high enantioselectivity (80–94% ee) under visible light conditions when employing a chiral rhodium Lewis acid as a catalyst (2 mol%).

An enantioselective crossed [2+2] photocycloaddition is presented which proceeds under visible light irradiation in the presence of a chiral Lewis acidic metal complex. Chelation of two oxygen atoms to the metal centre accounts for the observed enantioface differentiation.     

Structural parameters of the network formed first in in-situ sequential interpenetrating polymer networks

As part of a study concerning poly(propylene glycol)-based polyurethane / poly(methyl methacrylate) interpenetrating polymer networks, polyurethane networks were synthesized at various dilutions of the reaction medium and at different values of the [NCO]/[OH] ratio. The network defects arising in such materials were evaluated by three independent experimental approaches: solvent extraction, swelling behaviour, and compression measurements. It was found that the networks with the least defects are formed at high precursor concentration, with a [NCO] over [OH] excess of about 7%.