Refractive Indices of Aqueous Solutions of Isomeric Butylamines at 303.15 K: Experimental and Correlative Approach

Refractive indices () and densities (r) of water (W) + n-butylamine (NBA), + sec-butylamine (SBA) and + tert-butylamine (TBA) systems had been measured in the whole range of composition at 303.15 K, from which deviation in refractive index (DnD ) molar refraction (Rm) and excess molar refraction () had been evaluated. All of the derived properties were fitted to appropriate polynomials. DnD were fitted to the Redlich-Kister polynomial equation. Values of DnD were all positive and were all negative which were attributed to cross hydrogen bonding, specific interactions as well as interstitial accommodation effect. A comparative study of Lorentz-Lorenz (L-L), Weiner (W), Heller (H), Gladstone-Dale (G-D), Arago-Biot (A-B), Eykman (Eyk), Newton (Nw), Eyring-John (E-J) and Oster (Os) relations for determining the refractive index of a liquid had been carried out to test their validity for the three binaries over the entire mole fraction range of butylamines at 303.15 K.

Solvating Alkylamine Hofmann Elimination in Zeolites Through Cooperative Adsorption

<p>A kinetic investigation of the vapor phase Hofmann elimination of tert-butylamine over H-ZSM-5 reveals a carbocation mediated E1-like mechanism, where isobutene and ammonia are exclusively produced over Brønsted acid sites. Hofmann elimination kinetics are found to be insensitive to Al content or siting, varying only with alkylamine carbocation stability (r_tertiary > r_secondary > r_primary). Under conditions of complete tert-butylamine surface coverage, experimentally measurable apparent kinetics are directly equivalent to the intrinsic kinetics of the rate determining unimolecular surface elimination. The direct measurement of elementary step kinetics served as a water-free reactive probe, providing a direct measurement of the impact of water on solid Brønsted acid catalyzed chemistries at a microscopic level. Over a range of temperatures (453‒513 K) and tert-butylamine partial pressures (6.8×10^-2‒6.8 kPa), water reversibly inhibits the rate of Hofmann elimination. Despite expected changes in aluminosilicate hydrophobicity, the water-induced inhibition is found to be insensitive to Al content, demonstrated to be due to one water molecule per Brønsted acid site. Regardless of the significant reduction in the rate of Hofmann elimination, kinetic interrogations and operando spectroscopic measurements reveal that the coverage of TBA adsorbed on H-ZSM-5 is unaltered in the presence of water. Cooperative adsorption between the tert-butylammonium surface reactant and water adsorbed on a neighboring framework oxygen is proposed to be responsible for the observed rate inhibition, the surface dynamics of which is quantitatively captured through kinetic modeling of experimental rate measurements.</p>

Solvating Alkylamine Hofmann Elimination in Zeolites Through Cooperative Adsorption

<p>A kinetic investigation of the vapor phase Hofmann elimination of tert-butylamine over H-ZSM-5 reveals a carbocation mediated E1-like mechanism, where isobutene and ammonia are exclusively produced over Brønsted acid sites. Hofmann elimination kinetics are found to be insensitive to Al content or siting, varying only with alkylamine carbocation stability (r_tertiary > r_secondary > r_primary). Under conditions of complete tert-butylamine surface coverage, experimentally measurable apparent kinetics are directly equivalent to the intrinsic kinetics of the rate determining unimolecular surface elimination. The direct measurement of elementary step kinetics served as a water-free reactive probe, providing a direct measurement of the impact of water on solid Brønsted acid catalyzed chemistries at a microscopic level. Over a range of temperatures (453‒513 K) and tert-butylamine partial pressures (6.8×10^-2‒6.8 kPa), water reversibly inhibits the rate of Hofmann elimination. Despite expected changes in aluminosilicate hydrophobicity, the water-induced inhibition is found to be insensitive to Al content, demonstrated to be due to one water molecule per Brønsted acid site. Regardless of the significant reduction in the rate of Hofmann elimination, kinetic interrogations and operando spectroscopic measurements reveal that the coverage of TBA adsorbed on H-ZSM-5 is unaltered in the presence of water. Cooperative adsorption between the tert-butylammonium surface reactant and water adsorbed on a neighboring framework oxygen is proposed to be responsible for the observed rate inhibition, the surface dynamics of which is quantitatively captured through kinetic modeling of experimental rate measurements.</p>

Fluorinated Organic Paramagnetic Building Blocks for Cross-Coupling Reactions

New stable polyfluorinated nitroxide radicals for use in cross-coupling reactions, namely, N-tert-butyl-N-oxyamino-2,3,5,6-tetrafluoro-4-iodobenzene and N-tert-butyl-N-oxyamino-2,3,5,6-tetrafluoro-4-ethynylbenzene, were prepared from perfluoroiodobenzene. The reaction of the polyfluoro derivative with tert-butylamine under autoclaving conditions leading to the formation of N-tert-butyl-2,3,5,6-tetrafluoro-4-iodoaniline proved to be the key stage of the whole process. The fluorinated tert-butyl iodophenyl nitroxide was found to form in a solid state via N–O···I halogen bonds, a one-dimensional assembly of the radicals. The acceptor role of the nitroxide group in the halogen bonding changes to a donor role when the nitroxide reacts with Cu(hfac)2. In the last case, zero-dimensional assembly prevails, giving a three-spin complex with axial coordinated nitroxide groups and, as a consequence, causing ferromagnetic intramolecular exchange interactions between Cu(II) and radical spins.