Eine einfache Synthese von Tetraalkylammoniumsalzen mit funktionellen Anionen

Bichloride-based ionic liquids for the merged storage, processing, and electrolysis of hydrogen chloride

Hydrogen chloride is produced as a by-product in industrial processes on a million-ton scale. Since HCl is inherently dangerous, its storage and transport are avoided by, e.g., on-site electrolysis providing H2 and Cl2 which usually requires complex cell designs and PFAS-based membranes. Here we report a complementary approach to safely store 0.61 kilogram HCl per kilogram storage material [NEt3Me]Cl forming the bichloride [NEt3Me][Cl(HCl)n]. Although HCl release is possible from this ionic liquid by heat or vacuum, the bichloride can be used directly to produce base chemicals like vinyl chloride. Alternatively, [NEt3Me][Cl(HCl)n] is electrolyzed under anhydrous conditions using a membrane-free cell to generate H2 and the corresponding chlorination agent [NEt3Me][Cl(Cl2)n], enabling the combination of these ionic liquids for the production of base chemicals.

Electrochemical Nitration with Nitrite

Aromatic nitration has tremendous importance in organic chemistry as nitroaromatic compounds serve as versatile building blocks. This study represents the electrochemical aromatic nitration with NBu4 NO2 , which serves a dual role as supporting electrolyte and as a safe, readily available, and easy-to-handle nitro source. Stoichiometric amounts of 1,1,1-3,3,3-hexafluoroisopropan-2-ol (HFIP) in MeCN significantly increase the yield by solvent control. The reaction mechanism is based on electrochemical oxidation of nitrite to NO2 , which initiates the nitration reaction in a divided electrolysis cell with inexpensive graphite electrodes. Overall, the reaction is demonstrated for 20 examples with yields of up to 88 %. Scalability is demonstrated by a 13-fold scale-up.

Halogen bonding of electrophilic bromocarbons with pseudohalide anions

Spectral, thermodynamic and structural features of the complexes of bromocarbons with polydentate azide, cyanate or thiocyanate anions are presented. They suggest a significant role of the molecular-orbital interactions in formation of these halogen-bonded associates.

Is universal, simple melting point prediction possible?

An investigation of the melting points of 520 organic 1:1 salts is presented with the aim of developing a universal, simple, physically well-founded prediction scheme. The general reliability and reproducibility of the recorded experimental data are discussed with respect to purity, phase behavior, disorder and thermal history of a given substance. Additionally, mistakes, systematic errors, or lack of conventions can lead to considerable differences in the experimental measurements. A rough error bar for the reproducibility of the melting points of organic salts of ±5 to ±15 °C can be assigned. With this restraint, we developed two simple, semiempirical, five- and nine-parameter schemes with easy-to-calculate quantities. With these, we could predict the melting temperature of a given organic salt in the temperature range of -25 to +300 °C with an average error of 33.5 °C and a relative error of 9.3%. All calculated quantities are assessed with the help of conventional DFT, COSMO and COSMO-RS calculations, and are currently implemented into the IL-Prop module of the upcoming version of COSMOtherm. These prediction schemes are suitable for high-throughput computational screening of substances in the context of "computer-aided synthesis". Therefore, they are valuable tools to find a compound with a suitable melting point before its first synthesis.

Thermochemistry of Oxo Transfer from Coordinated Nitrite in the Dinitro(5,10,15,20-tetrakis(o-pivalamidophenyl)porphinato)iron(III) Anion

The thermochemistry of oxo transfer from coordinated nitrite in the dinitro(5,10,15,20-tetrakis(o-pivalamidophenyl)porphinato)iron(III) anion, ion-paired with the tetrapropylammonium ion, {[Fe(III)TpivPP(NO(2))(2)](-)Pr(4)N(+)}, has been evaluated in acetonitrile solution. This oxo-transfer half-reaction of {[Fe(III)TpivPP(NO(2))(2)](-)Pr(4)N(+)} has been assessed on the basis of the determination of the E(1/2) = +0.54 V vs SHE for the reversible [Fe(II/III)TpivPP(NO)(NO(2))](-)(/0) couple and the measurement of the formation constants for the association of NO and NO(2)(-) with the mononitroiron(III) porphyrin derivative. The formation constant for nitric oxide association, K(NO), has the value (1.21 +/- 0.08) x 10(3). The stability constant, K(2), for association of a second nitro ligand in 0.0100 M tetrapropylammonium perchlorate medium has been estimated as 2.18 x 10(3). The oxo-transfer half-reaction free energy, DeltaG degrees ((X/XO)), for addition of oxygen to [Fe(II)TpivPP(NO)(NO(2))](-) to form {[Fe(III)TpivPP(NO(2))(2)](-)Pr(4)N(+)} has been found to be -50 kJ/mol.

On the mechanism of action of methylmalonyl-CoA mutase. Change of the steric course on isotope substitution

When (methyl-2H3)methylmalonyl-CoA was reacted with partially purified methylmalonyl-CoA mutase, 1H-NMR revealed that about 24% of the migrating deuterium was lost after 88% conversion. When [methyl-3H]methylmalonyl-CoA was incubated with highly purified methylmalonyl-CoA mutase, tritium exchange with the medium depended on added methylmalonyl-CoA epimerase. With highly purified preparations of methylmalonyl-CoA mutase, effective tritium exchange from [5'-3H]adenosylcobalamin to water required the addition of methylmalonyl-CoA epimerase and of substrate (e.g. succinyl-CoA). By addition of [14C]succinyl-CoA to a partially purified preparation of methylmalonyl-CoA mutase, it was shown that the mutase binds one substrate molecule very tightly. Coupling the mutase reaction with the transcarboxylase reaction and using variously labelled succinyl-CoA as substrate, revealed that only (2R)- and not (2S)-methylmalonyl-CoA will be formed by the mutase with a kinetic isotope effect of 3.5 using (2H4)succinyl-CoA. When (1-13C) propionyl-CoA was reacted with a mixture of highly purified methylmalonyl-CoA carboxylase, epimerase and mutase, 13C-NMR signals were obtained for the thioester carbonyl of succinyl-CoA (relative intensity 100%) and of methylmalonyl-CoA (5%) as well as for the carboxyl of free succinic acid (27%) and of succinyl-CoA (less than 4.5%). Thus very little, if any, migration of the CoA from one carboxyl to the other appears to take place. (1,4-13C2)Succinic acid and (1,4-13C2)succinyl-CoA were synthesised and their 13C-NMR chemical shifts were exactly determined. Evidence is provided for a strict stereospecificity of the mutase toward the (2R)-epimer of methylmalonyl-CoA and for an incomplete stereospecificity toward the two diastereotopic 3-H atoms of succinyl-CoA. The latter, combined with a high intramolecular isotope discrimination, causes rapid washing-out of the migrating 2H and 3H to water and slow washing-in from the medium. Whenever migration of protium from the sterically less preferred 3-pro(S)- position of succinyl-CoA occurs and simultaneously a heavy isotope is maneuvered from the migratable 3-pro(R)- position into the labile alpha-position of methylmalonyl-CoA, the substitution by the COSCoA group takes place with inversion of configuration. When the sterically preferred 3-pro(R)-hydrogen atom migrates, the previously reported stereochemical retention occurs. A mechanistic and stereochemical scheme is discussed that fully accounts for all observations.