RISM-SCF study of the free-energy profile of the Menshutkin-type reaction NH3+CH3Cl→NH3CH3++Cl− in aqueous solution

The free-energy profile for the Menshutkin-type reaction NH₃ + CH₃Cl → NH₃CH₃ ⁺ + Cl⁻ in aqueous solution is studied using the RISM-SCF method. The effect of electron correlation on the free-energy profile is estimated by the RISM-MP2 method at the HF optimized geometries along the reaction coordinate. Solvation was found to have a large influence on the vibrational frequencies at the reactant, transition state and product; these vibrational frequencies are utilized to calculate the zero-point energy correction of the free-energy profile. The computed barrier height and reaction exothermicity are in reasonable agreement with those of experiment and previous calculations. The change of solvation structure along the reaction path is represented by radial distribution functions between solute-solvent atomic sites. The mechanisms of the reaction are discussed from the view points of solute electronic and solvation structures. Received: 26 June 1998/Accepted: 28 August 1998 / Published online: 2 November 1998     

A novel acid promoted ring‐opening polymerization of a seven‐membered cyclic carbonate initiated with BCl3

Ring‐opening polymerization of a seven‐membered cyclic carbonate, 1,3‐dioxepan‐2‐one, was investigated with a novel initiator system, BCl₃‐HCl·Et₂O. Addition of HCl·Et₂O promoted the polymerization even at 0°C to produce the corresponding polycarbonate with controlled molecular weight and narrow polydispersity ratio (< 1.2).     

Correlation Length Measurement of Sidewall Roughness of Dry Etched Facet and Its Effect on Reflectivity

Dry etching is an important tool to fabricate various semiconductor photonic devices. The roughness of etched sidewalls should be avoided as it reduces the scattering loss. We present a spatial frequency analysis of the sidewall roughness of dry etched facets processed by reactive ion etching. A characteristic parameter corresponding to a correlation length is estimated to be ∼0.5 μm. In addition, its effect on reflectivities of etched reflectors is discussed.     

Radical ring‐opening polymerization

The radical ring‐opening polymerization (RROP) behavior of the following monomers is reviewed, and the possibility for application to functional materials is described: cyclic disulfide, bicyclobutane, vinylcyclopropane, vinylcyclobutane, vinyloxirane, vinylthiirane, 4‐methylene‐1,3‐dioxolane, cyclic ketene acetal, cyclic arylsulfide, cyclic α‐oxyacrylate, benzocyclobutene, o‐xylylene dimer, exo‐methylene‐substituted spiro orthocarbonate, exo‐methylene‐substituted spiro orthoester, and vinylcyclopropanone cyclic acetal. RROP is a promising candidate for producing a wide variety of environmentally friendly functional polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 265–276, 2001     

Stereoselective Thermal Conversion of s-trans-Diallene into Dimethylenecyclobutene via s-cis-Diallene in the Crystalline State

A conrotatory [2+2] cyclization is the second step in the solid-state thermal reaction of s-trans-tetraaryldibromohexatetraenes 1 to cyclobutenes 4 . Prior to the cyclization 1 rearranges into the cis conformer 3 . Surprisingly the thermal rearrangement and the stereoselective cyclization occur readily in spite of the required motion of the sterically bulky substituents. R=Ph, p-MeC₆H₄.     

Novel one-pot syntheses of sulfur-containing polymers from a bifunctional five-membered cyclic dithiocarbonate

Novel one-pot syntheses of sulfur-containing polymers from a bifunctional five-membered cyclic dithiocarbonate ( 1a ) were carried out. Polythiourethanes were obtained by the polyaddition of 4,4′-methylenebis(phenyl isocyanate), tolylene 2,6-diisocyanate, and hexamethylene diisocyanate with a dithiol ( 2a ) obtained by the reaction of 1a and benzylamine under mild conditions. Polythioesters were also obtained by the polycondensation of terephthaloyl and succinyl chlorides with 2a . Further, polythioether was obtained by the polycondensation of α,α′-dibromo-p-xylene with 2a . © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1189–1195, 1998     

Radical ring-opening polyaddition of a bifunctional vinylcyclopropane bearing a spiroacetal moiety with dithiols

Radical polyadditions of vinylcyclopropane having spiroacetal moiety, 1,10-divinyl-4,8,12,15-tetraoxatrispiro[2.2.2.2.2.2] pentadecane ( 1 ), and various dithiols were examined. 1 was prepared by the reaction of 1,1-dichloro-2-vinylcyclopropane and pentaerythritol, and radical polyadditions of 1 and dithiols were carried out at 60 and 120°C for 20 h in the presence of an appropriate initiator (3 mol % vs. 1 ) in degassed sealed ampoules or at 20°C under photo irradiation by using a 400 W high-pressure mercury lamp. Poly( 1 ), pale yellow transparent viscous polymers was isolated by reprecipitation with ether containing a small amount of triethylamine to avoid hydrolysis of the polymer. The obtained polymers were soluble in chlorobenzene, DMF, and chloroform but insoluble in ether and n-hexane. The molecular weights of the polymers obtained from aliphatic dithiols were smaller than those from aromatic ones. The structure of the polymer was determined by comparing the NMR spectra with those of the model compounds, which were obtained by radical addition of 1 and benzyl mercaptan. The reaction proceeded through radical polyaddition of dithiol to 1 via radical ring-opening polymerization of the cyclopropane ring. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2487–2492, 1997     

Activated monomer cationic polymerization of 1,3-dioxepan-2-one initiated by water-hydrogen chloride

The ring-opening polymerization of 1,3-dioxepan-2-one (7CC) was carried out by water-hydrogen chloride as an initiator to obtain the corresponding polymer with the molecular weight controlled by the amount of water. A ¹H NMR spectroscopic study suggests that the chain growth in this system is based on the attack of the terminal hydroxyl group to the monomer activated with hydrogen chloride.