2754-54-3Relevant academic research and scientific papers
Effect of Crown Ether Lipophilicity on the Facilitated Transport of Guanidinium Thiocyanate through an Immobilized Liquid Membrane
Stolwijk, Theodorus B.,Sudhoelter, Ernst J. R.,Reinhoudt, David N.
, p. 6321 - 6329 (1989)
The flux of guanidinium thiocyanate through a supported liquid membrane has been measured for substituted benzo crown ethers and dibenzo crown ethers.This flux depends on the water solubility of the carrier.The more lipophilic crown ethers (7-14 and 16) show a higher flux and form more stable supported liquid membranes.The effect of the lipophilic substituents on the partition coefficient of the benzo crown ethers has been calculated and verified by partition experiments.The observed fluxes have been interpreted by a developed general model for the transport of salts through supported liquid membranes containing crown ethers.This thermodynamic model takes into account the interface equilibria, viz. the partition of crown ether and salt, as well as complexation equilibria in the membrane and aqueous phase.The model has been applied for the calculation of the complexation constants in the membrane phase.The lipophilic benzo crown ethers with 27 ring atoms show lower complexation constants than the corresponding benzo crown ether with 30 ring atoms.The complexation constants of the dibenzo crown ethers and guanidinium thiocyanate are smaller than those of the corresponding complexes of the substituted benzo crown ethers.During the diffusion process of the complex through the membrane phase complexation and decomplexation take place continuously as was concluded from the small value of the inverse Damkoehler number.
Selective acylation of phenols in boron trifluoride diethyl etherate solution and the mechanistic implication
Xiao, Zhu-Ping,Wei, Wei,Huang, Shen,Lin, Xiao-Yi,Peng, Bin,Wang, Xu-Dong,Zhang, Lei
, p. 8039 - 8042 (2015/02/02)
In the presence of boron trifluoride diethyl etherate (BF3 · OEt2), direct acylation of phenols with free carboxylic acid is chemoselective and regioselective and no demethylation, if any, was observed. The para-directing effect of BF3·OEt2 is attributed to the large steric hindrance of the boron trifluoride-phenolic hydroxyl group complex, which blocks the ortho-acylation from occurrence. Microwave irradiation could not change the regioselectivity of BF3·OEt2 except the reaction time being greatly shortened.
