88563-46-6Relevant articles and documents
Kinetic and Thermodynamic Barriers to Carbon and Oxygen Alkylation of Phenol and Phenoxide Ion by the 1-(4-Methoxyphenyl)ethyl Carbocation
Tsuji, Yutaka,Toteva, Maria M.,Garth, Heather A.,Richard, John P.
, p. 15455 - 15465 (2007/10/03)
Rate constant ratios for addition of the three nucleophilic sites of phenol to the 1-(4-methoxyphenyl)ethyl carbocation (1+) in 50/50 (v/v) trifluoroethanol/water were determined from the relative yields of the three phenol adducts, and absolute rate constants were determined from product rate constant ratios for addition of phenol and azide ion to 1+ using kaz = 5 × 109 M-1 s-1 for the diffusion-limited reaction of azide ion. A selectivity of 230:20:1 was determined for alkylation of phenol at oxygen, C-4 and C-2 to form 1-OPh and biphenyls 1-(4-C6H4OH) and 1-(2-C6H 4OH), respectively, and of 2:2:1 for alkylation of the corresponding nucleophilic sites of phenoxide ion in diffusion-limited reactions. The Mayr nucleophilicity parameter for C-4 of phenol is N = 2.0. Encounter-limited addition of phenoxide ion to 1+ to form 1-OPh is faster than encounter-limited addition of oxygen anions that are either more or less basic than phenoxide ion. Only the products of solvolysis are observed from acid-catalyzed cleavage of 1-OPh in 50/50 (v/v) trifluoroethanol/water, but a 50% yield of biphenyls 1-(4-C6H4OH) and 1-(2-C 6H4OH) are observed from spontaneous cleavage of 1-OPh, where the leaving group is phenoxide ion, because of the very low kinetic barriers to collapse of the ion pair intermediate 1+.PhO -. The 230-fold larger rate constant for O-compared to C-2-alkylation of phenol is due primarily to the larger thermodynamic driving force for oxygen addition. There are similar Marcus intrinsic barriers for these two reactions.
Retentive Solvolysis. Part 12. Mechanism of the Reaction of Optically Active 1-(p-Methoxyphenyl)ethyl Trifluoroacetate with Phenol and Metanol in Benzene and Cyclohexane
Okamoto, Kunio,Takeuchi, Ken'ichi,Inoue,Takeshi
, p. 842 - 848 (2007/10/02)
The rate, product distribution, and stereochemical course for the reactions of 0.05-0.1M-1-(p-methoxyphenyl)ethyl trifluoroacetate (1) with methanol and phenol have been investigated in benzene or cyclohexane as solvent at 25.0 deg C.Below 1E-3M-methanol or -phenol the total kinetic order is two overall .The rates are virtually independent of the pyridine used to bind the trifluoroacetic acid produced.The major product from the phenol reaction, 1-(p-methoxyphenyl)ethyl phenyl ether, shows net retention (6-9percent) of configuration along with predominant racemization.In addition, the methyl ether product from the methanol reaction also undergoes net retention (24percent with 0.2M-methanol).The formation of the ethers with net retention of configuration can be accounted for by an intermolecular SNi mechanism.
