111-89-7Relevant academic research and scientific papers
Thermodynamic stabilities of Cu+ and Li+ complexes of dimethoxyalkanes (MeO(CH2)nOMe, n = 2-9) in the gas phase: Conformational requirements for binding interactions between metal ions and ligands
Mishima, Masaaki,Maeda, Hideyuki,Than, Soe,Irie, Maki,Kikukawa, Kiyoshi
, p. 616 - 623 (2006)
The relative free energy changes for the reaction ML+ = M + + L (M = Cu+ and Li+) were determined in the gas phase for a series of dimethoxyalkanes (MeO(CH2)nOMe, n = 2-9) by measuring the equilibrium constants of ligand-transfer reactions using a FT-ICR mass spectrometry. Stable 1:1 Cu+-complexes (CuL +) were observed when the chain is longer than n = 4 while the 1:2 complexes (CuL2+) were formed for smaller compounds as stable ions. The dissociation free energy for CuL+ significantly increases with increasing chain length, by 10 kcal mol-1 from n = 4 to 9. This increase is attributed to the release of constrain involved in the cyclic conformation of the Cu+-complexes. This is consistent with the geometrical and energetic features of the complexes obtained by the DFT calculations at B3LYP/6-311G level of theory. On the contrary, the corresponding dissociation free energy for LiL+ increases only 3 kcal mol -1 from n = 2 to 9, although the structures of the 1:1 Li +-complexes are also considered to be cyclic. From these results it is concluded that the Cu[MeO(CH2)nOMe]+ requires linear alignment for O-Cu-O, indicating the importance of sd σ hybridization of Cu+ in the first two ligands binding energy, while the stability of the Li+ complex is less sensitive to binding geometries except for the system forming a small ring such as n = 1 and 2. Copyright
Upgrading biomass-derived furans via acid-catalysis/hydrogenation: The remarkable difference between water and methanol as the solvent
Hu, Xun,Westerhof, Roel J. M.,Wu, Liping,Dong, Dehua,Li, Chun-Zhu
, p. 219 - 224 (2018/04/16)
In methanol 5-hydroxymethylfurfural (HMF) and furfuryl alcohol (FA) can be selectively converted into methyl levulinate via acidcatalysis, whereas in water polymerization dominates. The hydrogenation of HMF, furan and furfural with the exception of FA is
Fingerprinting a Transition-Structure Guest by a Building-Block Approach with an Incremental Series of Catalytic Hosts. Structural Requirements for Glyme and α,ω-Dimethoxyalkane Catalyses in N-Methylbutylaminolysis and Butylaminolysis of 4-Nitrophenyl Acetate in Chlorobenzene
Hogan, John C.,Gandour, Richard D.
, p. 55 - 61 (2007/10/02)
Glymes, H-(CH2OCH2)n-H, GLM(n), catalyze butylaminolysis of 4-nitrophenyl acetate in chlorobenzene.Values of kcat/Oxy, where Oxy is the number of oxygens in the catalyst, increase with oligomer length up to triglyme, GLM(4), and then plateau.Optimal catalysis on a per oxygen basis requires a -(CH2OCH2)4-fragment, which suggests a four-point recognition of the secondary ammonium ion of the zwitterionic tetrahedral intermediate (TI) (J.Org.Chem. 1991, 56, 2821-2826).Dissection of individual structural components and reassembly to the same structure of the complexverifies this model.The following kinetic studies of 4-nitrophenyl acetate in chlorobenzene have accomplished the task: (a) methylbutylaminolysis catalyzed by GLM(n), n = 2-4; (b) methylbutylaminolysis catalyzed by α,ω-dimethoxyalkanes, CH3O-(CH2)n-OCH3, DME(n), n = 2-10 and 12; and (c) butylaminolysis catalyzed by DME(n), n = 2-10 and 12.Experiment a has revealed that kcat/Oxy is the same for GLM(2) - GLM(4).Optimal catalysis for breakdown of a zwitterionic TI with one ammonium proton only requires a -(CH2OCH2)2-fragment.Experiment b has shown that kcat/Oxy is largest for DME(2) with the values for the remaining DMEs 2 - 2.5-fold lower.A -CH2CH2- is the best spacer between the two oxygens.Thus, bifurcated hydrogen-bond formation between the two oxygens and the one ammonium proton enhances catalysis.Experiment c has revealed that kcat/Oxy for DME(2) exceeds the remaining DMEs by 3 - 3.6-fold, except for DME(8) and DME(10), which have values of kcat/Oxy only 1.7-fold slower.DME(8), the carba analogue of GLM(4), likely binds the two ammonium protons individually with the two oxygens.DME(10) behaves similarly.GLM(4) catalysis of butylaminolysis identifies -(CH2OCH2)4- as an optimal size.DME(8) catalysis confirms this size, although the two catalysts stabilize the two-proton ammonium ion differently.GLM(4) catalyzes butylaminolysis by forming two bifurcated hydrogen bonds.This suggested structure defines the size of the ammonium ion, which agrees with X-ray structural studies of polyether-ammonium complexes.Mechanistic proposals of butylaminolysis of aryl esters require such an ion.The results of this study confirm the stucture of the ion in the rate-limiting step.This building-block approach is a method for "fingerprinting" ammonium ions in transition structures of ionogenic reactions.
