Characteristics and Mechanism of Vinyl Ether Cationic Polymerization in Aqueous Media Initiated by Alcohol/B(C6F5)3/Et2O.

Aqueous cationic polymerizations of vinyl ethers (isobutyl vinyl ether (IBVE), 2-chloroethyl vinyl ether (CEVE), and n-butyl vinyl ether (n-BVE)) were performed for the first time by a CumOH/B(C6F5)3/Et2O initiating system in an air atmosphere. The polymerization proceeded in a reproducible manner through the careful design of experimental conditions (adding initiator, co-solvents, and surfactant or decreasing the reaction temperature), and the polymerization characteristics were systematically tested and compared in the suspension and emulsion. The significant difference with traditional cationic polymerization is that the polymerization rate in aqueous media using B(C6F5)3/Et2O as a co-initiator decreases when the temperature is lowered. The polymerization sites are located on the monomer/water surface. Density functional theory (DFT) was applied to investigate the competition between H2O and alcohol combined with B(C6F5)3 for providing a theoretical basis. The effectiveness of the proposed mechanism for the aqueous cationic polymerization of vinyl ethers using CumOH/B(C6F5)3/Et2O was confirmed.

Investigation of the interactions between 1-butyl-3-methylimidazolium-based ionic liquids and isobutylene using density functional theory.

To identify ionic liquids (ILs) that could be used as solvents in isobutylene (IB) polymerization, the interactions between IB and eight different ILs based on the 1-butyl-3-methylimidazolium cation ([Bmim]+) were investigated using density functional theory (DFT). The anions in the ILs were chloride, hexafluorophosphate, tetrafluoroborate, bis[(trifluoromethyl)sulfonyl]imide, tetrachloroaluminate ([AlCl4]-), tetrachloroferrate, acetate, and trifluoroacetate. The interaction geometries were explained by changes in the total energy, intermolecular distances, Hirshfeld charges, and the electrostatic potential surface. The IL solvents were screened by comparing their interaction intensities with IB to the interaction intensities of reference ILs ([AlCl4]--based ILs) with IB. The microscopic mechanism for IB dissolution was rationalized by invoking a previously reported microscopic mechanism for the dissolution of gases in ILs. Computation results revealed that hydrogen (H) bonding between C2-H on the imidazolium ring and the anions plays a key role in ion pair (IP) formation. The addition of IB leads to slight changes in the dominant interactions of the IP. IB molecules occupied cavities created by small angular rearrangements of the anions, just as CO2 does when it is dissolved in an IL. The limited total free space in the ILs and the much larger size of IB than CO2 were found to be responsible for the poor solubility of IB compared with that of CO2 in the ILs.

The effects of halogen elements on the opening of an icosahedral B12 framework.

The fully halogenated or hydrogenated B12X122- (X = H, F, Cl, Br and I) clusters are confirmed to be icosahedral. On the other hand, the bare B12 cluster is shown to have a planar structure. A previous study showed that a transformation from an icosahedron to a plane happens when 5 to 7 iodine atoms are remained [P. Farràs et al., Chem. - Eur. J. 18, 13208-13212 (2012)]. Later, the transition was confirmed to be seven iodine atoms based on an infrared spectroscopy study [M. R. Fagiania et al., Chem. Phys. Lett. 625, 48-52 (2015)]. In this study, we investigated the effects of different halogen atoms on the opening of the B12 icosahedral cage by means of density functional theory calculations. We found that the halogen elements do not have significant effects on the geometries of the clusters. The computed infrared (IR) spectra show similar representative peaks for all halogen doped clusters. Interestingly, we found a blue-shift in the IR spectra with the increase in the mass of the halogen atoms. Further, we compared the Gibbs free energies at different temperatures for different halogen atoms. The results show that the Gibbs free energy differences between open and close structures of B12X7- become larger when heavier halogen atoms are presented. This interesting finding was subsequently investigated by the energy decomposition analysis.

Density functional study of structures and electron affinities of BrO4F/BrO4F-.

The structures, electron affinities and bond dissociation energies of BrO(4)F/BrO(4)F(-) species have been investigated with five density functional theory (DFT) methods with DZP++ basis sets. The planar F-Br...O(2)...O(2) complexes possess (3)A' electronic state for neutral molecule and (4)A' state for the corresponding anion. Three types of the neutral-anion energy separations are the adiabatic electron affinity (EA(ad)), the vertical electron affinity (EA(vert)), and the vertical detachment energy (VDE). The EA(ad) value predicted by B3LYP method is 4.52 eV. The bond dissociation energies D(e) (BrO(4)F --> BrO(4-m)F + O(m)) (m = 1-4) and D(e) (-) (BrO(4)F(-) --> BrO(4-m)F(-) + O(m) and BrO(4)F(-) --> BrO(4-m)F + O(m) (-)) are predicted. The adiabatic electron affinities (EA(ad)) were predicted to be 4.52 eV for F-Br...O(2)...O(2) ((3)A'<--(4)A') (B3LYP method).

Hypervalency avoided: simple substituted BrF3 and BrF5 molecules. Structures, thermochemistry, and electron affinities of the bromine hydrogen fluorides HBrF2 and HBrF4.

Five different pure density functional theory (DFT) and hybrid Hartree-Fock/DFT methods have been used to search for the molecular structures, thermochemistry, and electron affinities of the bromine hydrogen fluorides HBrF(n)/HBrF(n)(-) (n = 2, 4). The basis sets used in this work are of double-zeta plus polarization quality in conjunction with s- and p-type diffuse functions, labeled as DZP++. Structures with Br-F and Br-H normal bonds, that is, HBrF(2)/HBrF(2)(-) with C(2v) or C(s) symmetry and HBrF(4)/HBrF(4)(-) with C(4v) or C(s) symmetry, are genuine minima. However, unlike the original BrF(3) and BrF(5) molecules, the global minima for HBrF(n)/HBrF(n)(-) (n = 2, 4) species are predicted to be complexes, some of which contain hydrogen bonds. The demise of the hypervalent structures is due to the availability of favorable dissociation products involving HF, which has a much larger dissociation energy than F(2). Similar reasoning suggests that PF(4)H, SF(3)H, SF(5)H, ClF(2)H, ClF(4)H, AsF(4)H, SeF(3)H, and SeF(5)H will all be hydrogen bond structures incorporating diatomic HF. The most reasonable theoretical values of the adiabatic electron affinities (EA(ad)) are 3.69 (HBrF(2)) and 4.38 eV (HBrF(4)) with the BHLYP method. These electron affinities are comparable to those of the analogous molecules: Br(2)F(n), ClBrF(n), and BrF(n)(+1) systems. The first F-atom dissociation energies for the neutral global minima are 60 (HBrF(2)) and 49 kcal/mol (HBrF(4)) with the B3LYP method. The first H-atom dissociation energies for the same systems are 109 (HBrF(2)) and 116 kcal/mol (HBrF(4)). The large Br-H bond energies are not sufficient to render the hypervalent structures energetically tenable. The dissociation energies for the complexes to their fragments are relatively small.