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A facile and efficient method is described for the cleavage of the Ar-Si bond of various aryl trimethyl silanes. These arylsilanes have readily undergone a solvent-free protodesilylation to the corresponding arenes at room temperature, when adsorbed on montmorillonite KSF (mont KSF).

Reinvestigation of the molecular structure of tetracyclohexylmethane reveals that it exists in the crystal in a (g/a/-g) conformation and the rings are skewed from their perfectly staggered D2d conformation. Crystallographic conformation is the lowest energy form, as revealed by molecular mechanics calculations. Multinuclear NMR experiments reveal the occurrence of fast rotational process in these molecules, leading to topomerization. A transition state of D2d symmetry is associated with the rotational pathway involving libration of the four rings.

Tetracyclohexylethene in tongue and groove arrangement is prepared and analyzed to study the conformational phenomenon in the polycyclohexyl system. Conformations of two methylene groups at methine carbon are restricted due to the presence of a ring. Crystallographic analysis reveals the deep introduction of syn rings methine hydrogens in the grooves. Higher conformational barrier is observed due to restricted rotations of cyclohexyl rings.

Two dimensional NMR methods INADEQUATE and DQF COSY were used to assign C and H NMR of tricyclohexylmethane. Molecular mechanics computations were carried out to analyze the impact of torsional angles of the cyclohexyl rings and their patterns of attachment on the relative energy of the conformations. This was a part of the study of static and dynamic stereochemistry of tricyclohexylmethane.

The degradation of the warfare agent sulfur mustard (HD) adsorbed onto KF/[Al.sub.2][O.sub.3] sorbents is described and analyzed by MAS NMR. The detoxification of the blister agent has showed the formation of nontoxic substitution and less-toxic elimination products and the reaction rates are affected by MAS conditions.

The reaction under [S.sub.N]1 conditions of the hexabromo calixarene derivative with the appropriate nucleophile was used to prepare calix[6]arenes derivatives monosubstituted at all bridges. The reaction could use wide array of nucleophiles such as alcohols, azide ion, aniline, benzene derivatives and even with acetylacetone.

The scope of the reaction of the tetrabromocalixarene derivative with alcohols under solvolytic conditions in trifluoroethanol (TFE) or hexafluoroisopropanol (HFIP) is analyzed. The reaction of de-tert-butylated tetrabromo derivative with m-xylene in HFIP followed by methylation of the crude product has afforded the tetraxylyl derivative.

The advantages and limitations of (super 31)P diffusion NMR in corroborating the type of species that prevail in these systems are discussed. (super 31)P diffusion NMR is a useful tool for characterizing enzyme, which adduct arrays in systems where the (super 1)H NMR spectra are noninformative because of relatively short T2.

A study was conducted to analyze face selectivity during the hydrogenation of calixarene ethers. Attacks on the face of the symmetry-equivalent rings were examined using 13C nuclear magnetic resonance spectroscopy. Results indicated that the hydrogenation of atropisomers of calix(4)arene derivatives supports an exo, all-syn method. In addition, the judicious selection of the atropisomeric starting material supported control of the pattern of stereocenters in the hydrogenated product.

In the present study, we applied for the first time 31P diffusion NMR to resolve different species obtained by the addition of organophosphorus compounds (OP) such as diisopropyl phosphorofluoridate (DFP) or 1-pyrenebutyl phosphorodichioridate (PBPDC) to α-chymotrypsin (Cht). 31P diffusion NMR was used since the products of these reactions constitute a mixture of OP-covalent conjugates of the enzyme and OP-containing hydrolysis products that have noninformative ¹H NMR spectra. It was shown that the peak, attributed to the covalent native diisopropylphosphoryl-Cht (DIP-Cht) conjugate by chemical shift considerations, has a greater diffusion coefficient (D = (0.65 ± 0.01) × 10-5 cm² s-1) than expected from its molecular mass (approximately 25 kDa). This peak was therefore suggested to consist of at least two superimposed signals of diisopropyl phosphoryl (DIP) pools of high and low molecular weights that happen to have the same chemical shift. This conclusion was substantiated by the use of DMSO-d6 that separated the overlapping signals. Diffusion measurements performed on the extensively dialyzed and unfolded DIP-Cht conjugate still resulted in a high diffusion coefficient ((0.30 ± 0.05) × 10-5 cm² s-1) relative to the assumed molecular mass. This observation was attributed to a dynamic dealkylation at the OP moiety (i.e., aging) that occurred during the relatively long diffusion measurements, where DIP-Cht was converted to the corresponding monoisopropyl phosphoryl Cht (MIP-Cht) conjugate. Homogeneous aged forms of OP-Cht were obtained by use of DFP and heat-induced dealkylation of DIP-Cht, and by PBPDC that provided the aged form via the hydrolysis of a P-Cl bond (PBP-Cht). The thermally stable aged conjugates enabled a reliable determination of the diffusion coefficients over several days of data acquisition, and the values found were (0.052 ± 0.002) × 10-5 cm² s-1 and (0.054 ± 0.004) × 10-5 cm² s-1 for the MIP-Cht and the PBP-Cht adducts, respectively, values in the range expected for a species with a molecular weight of 25 kDa. The advantages and limitations of 31P diffusion NMR in corroborating the type of species that prevail in such systems are briefly discussed. [ABSTRACT FROM AUTHOR]

Active gels present unique potential for the decontamination of chemical warfare agents (CWAs) as they strongly adhere to surfaces, thus allowing prolonged decontamination time. Herein, we present a decontamination hydrogel based on polyvinyl alcohol/borax, which contains sodium perborate (NaBO 3 ), as an in situ source of the active ingredient hydrogen peroxide. Developed as a binary formulation, this gel instantly forms and effectively sticks when sprayed on various matrices, including porous and vertically positioned matrices. The gel efficiently detoxified the CWAs sarin (GB), O -ethyl S -2-(diisopropylamino)ethyl methylphosphonothioate (VX), and sulfur mustard (HD) in test tubes (2 μL CWA/0.5 mL gel) to provide nontoxic products with reaction half-lives of <3, 45 and 113 min, respectively. The gel was also shown to efficiently decontaminate surfaces contaminated with VX (5-7 mg, 8-12 mL of gel, i.e., >99%) and to prevent GB evaporation, as proven by laboratory wind tunnel experiments. The universal decontamination abilities of this mild hydrogel, as well as its facile application and removal processes suggest that it holds high potential for future development as a new CWA decontamination tool., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Solvent effects on the ability of KF/Al 2 O 3 supports to degrade the warfare agent sulfur mustard (HD) were explored. RP-KF/Al 2 O 3 possessing hydroxide ions and ECUF/KF/Al 2 O 3 holding fluoride ions were examined. Reactions on RP-KF/Al 2 O 3 containing 10 wt % of organic solvents were faster than those on ECUF/KF/Al 2 O 3 . Additionally, RP-KF/Al 2 O 3 led to elimination products, while ECUF/KF/Al 2 O 3 mainly led to substitution derivatives. Enlarging the solvent amounts to 90 wt % resulted in decreased reaction rates. The significance of solvent identity/amount and active species is discussed.