102-09-0 A kinetic study on ethylaminolysis of phenyl y-substituted-phenyl carbonates: Effect of leaving-group substituents on reactivity and reaction mechanism

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A kinetic study on nucleophilic substitution reactions of phenyl Y-substituted-phenyl carbonates (5a-5j) with ethylamine in 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 oC is reported. The plots of kobsd vs. [amine] are linear for the reactions of substrates possessing a strong electron-withdrawing group (EWG) but curve upward for those of substrates bearing a weak EWG, indicating that the electronic nature of the substituent Y in the leaving group governs the reaction mechanism. The reactions have been concluded to proceed through a stepwise mechanism with one or two intermediates (a zwitterionic tetrahedral intermediate T± and its deprotonated form T-) depending on the nature of the substituent Y. Analysis of Bronsted-type plots and dissection of kobsd into microscopic rate constants have revealed that the reactions of substrates possessing a strong EWG (e.g., 5a-5f) proceed through T± with its formation being the rate-determining step, while those of substrates bearing a weak EWG (e.g., 5g-5j) proceed through T± and T-. https://www.lookchem.com/CASDataBase_102-09-0.htm

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100-64-1 On the Oxidation of Hydroxylamines with o -Iodoxybenzoic Acid (IBX)

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10065-72-2 Crucigasterins, New Polyunsaturated Amino Alcohols from the Mediterranean Tunicate Pseudodistoma crucigaster

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Crucigasterins 277, 275, and 225, three new polyunsaturated amino alcohols, 10-12, were isolated from the Mediterranean tunicate Pseudodistoma crucigaster.The structures of these compounds were assigned based on NMR and FABMS data.Absolute stereochemistry of the amino alcohol portion in 10 was assigned to be 2R,3S based on chiral GC comparison of 3-hydroxy-4-aminopentanoic acid 13d, a chemical degradation product of 10, with a synthetic sample prepared from L-alanine.Compounds 10-12 exhibited moderate cytotoxicity and antimicrobial activity. https://www.lookchem.com/CASDataBase_10065-72-2.htm
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