1693-74-9Relevant articles and documents
Proton Chemical Shifts and Thermodynamics of the Formation of Hydrogen-Bonded Dimers and Mixed 1:1 Associates in the Ternary System Acetic Acid/Methanol/Tetrahydrofuran-d8
Gerritzen, Detlef,Limbach, Hans-Heinrich
, p. 799 - 805 (1980)
The chemical shifts of the carboxylic proton of acetic acid and of the hydroxylic proton of methanol dissolved together and separately in tetrahydrofuran-d8 were determined as a function of the temperature and the solute concentrations.The determination of these chemical shifts was possible because in very pure samples the line positions are not affected by proton-exchange reactions.The data can only be explained by the presence of the following association reactions between hydrogen-bonded species which involve the solvent, S: RCOOH...S + RCOOH...S RCOOH...RCOOH...S + S RCOOH...S +ROH...S RCOOH...ROH...S + S ROH...S + RCOOH...S ROH...RCOOH...S + S ROH...S + ROH...S ROH...ROH...S + S The reaction enthalpies are given by +4.2, -1.4, -3.0, and -3.3 kJ mol-1, the reaction entropies at 298 K by +0.3, -3, -9, and -16 J K-1 mol-1.These data are not very far from zero, indicating that the number of hydrogen bonds remains constant during the association.Nevertheless, the extent of association is very low, and the quasi monomers which are hydrogen bonded to the solvent dominate.This arises from the high concentration, cs, of the free solvent.The change of cs at higher solute concentrations has to be taken into account in the treatment of the experimental data.Similarly, hydrogen bonding between the donors and the solvent is the reason that cyclic 1:1 associates and higher associates are not observed and the reason for the slow proton exchange.It is shown that the thermodynamic data of proton donor association in different media obey linear enthalpy-entropy relationships which are typical for the functional proton donor group.
Mono and dimetallic pyrene-imidazolylidene complexes of iridium(III) for the deuteration of organic substrates and the C-C coupling of alcohols
Iba?ez,Poyatos,Peris
, p. 14154 - 14159 (2016/11/15)
Three different Ir(iii) complexes with pyrene-containing N-heterocyclic carbenes have been prepared and characterized. Two complexes contain a monodentate pyrene-imidazolylidene ligand, and have the formulae [IrCp?Cl2(pyrene-NHC)] and [IrCp?(CO3)(pyrene-NHC)]. The third complex is a dimetallic complex with a pyrene-di-imidazolylidene bridging ligand, with the formula [{IrCp?(CO3)}2(μ-pyrene-di-NHC)]. The catalytic activity of the three complexes was tested in the H/D exchange of organic substrates, and in the β-alkylation of 1-phenylethanol with primary alcohols. In the deuteration of organic substrates, the carbonate complexes are active even in the absence of additives. The dimetallic complex is the most active one in the catalytic coupling of alcohols, a result that may be interpreted as a consequence of the cooperativity between the two metal centres.
Iridium-catalyzed H/D exchange into organic compounds in water
Klei, Steven R.,Golden, Jeffrey T.,Tilley, T. Don,Bergman, Robert G.
, p. 2092 - 2093 (2007/10/03)
The air-stable complex Cp*(PMe3)IrCl2 efficiently catalyzes the exchange of deuterium from D2O into both activated and unactivated C-H bonds of organic molecules without added acid or stabilizers. Selectivity is observed in many cases, with activation of primary C-H bonds occurring preferentially. A number of new stoichiometric transformations involving the iridiym catalyst precursor are also presented, including an ozidation-decarbonylation reaction with primary alcohols. Copyright
