Xi:Irritant;2917-26-2Relevant articles and documents
Proximity effects in monolayer films: Kinetic analysis of amide bond formation at the air-water interface using 1H NMR spectroscopy
Kumar, Jaya K.,Oliver, John S.
, p. 11307 - 11314 (2002)
The kinetics of amide bond formation in a monolayer film has been studied by proton NMR spectroscopy. Compression of a hexadecyl thioester of N-acetyl glycine (1) and a hexadecyl amide of glycine (2) at the air-water interface produces a single dipeptide product (4) that remains at the surface once formed. Extraction of the reaction mixture from the interface, followed by 1H NMR spectroscopy, provides quantitative data on the rate of product formation. The kinetics of this reaction was examined as a function of surface pressure, subphase pH, and temperature. The monolayer provides an effective molarity for the reaction of ～500 M as compared to the bimolecular reaction of 1 and 4 in chloroform solution. The first-order rate constant for the reaction of 1 and 2 in the monolayer is less than 70-fold slower than kcat for condensation of the first amide bond in the enzymatic synthesis of the cyclic antibiotic gramicidin S by gramicidin S synthetase. Activation energies of the reaction were extracted from the temperature dependence of the rate constants of the reaction and are 9.9 ± 1.0 and 2.1 ± 0.2 kcal/mol for the chloroform solution and monolayer reactions, respectively. The pKa of 2 in the monolayer was estimated to be ～0.5 pKa units lower than that of related amines in solution. The lower pKa at the interface as compared to that in solution may be ascribed to increased electrostatic repulsion at the interface relative to solution. The rate of reaction in the monolayer was also followed by monitoring changes in surface area as a function of time. The rate constant for the reaction of 1 and 4 as determined by changes in surface area differs significantly from the rate determined by NMR. The results indicate that measurements of surface area versus time may yield erroneous rate constants for reactions in monolayers.
Phosphorus pentasulfide mediated conversion of organic thiocyanates to thiols
Maurya, Chandra Kant,Mazumder, Avik,Gupta, Pradeep Kumar
supporting information, p. 1184 - 1188 (2017/07/03)
In this paper we report an efficient and mild procedure for the conversion of organic thiocyanates to thiols in the presence of phosphorus pentasulfide (P2S5) in refluxing toluene. The method avoids the use of expensive and hazardous transition metals and harsh reducing agents, as required by reported methods, and provides an attractive alternative to the existing methods for the conversion of organic thiocyanates to thiols.
One-pot synthetic method of allyl sulfides: Samarium-induced allyl bromide mediated reduction of alkyl thiocyanates and diaryl disulfides in methanolic medium
Zhan, Zhuang-Ping,Lang, Kai
, p. 1370 - 1371 (2007/10/03)
A convenient synthetic method of allyl sulfides by the treatment of alkyl thiocyanates or diaryl disulfides with Sm and allyl bromide in methanol has been developed.
