PMID: 11312943Apr 21, 2001Paper

Ion-dipole S(N)2 reaction in acetone-water mixtures. Electrostatic and specific solute-solvent interactions

The Journal of Organic Chemistry
E HumeresC Machado

Abstract

The rate constants of the S(N)2 reaction of sodium 4-nitrophenoxide (1) and iodomethane were determined by UV-visible spectrophotometry in acetone-water mixtures at 25, 30, and 35 degrees C. The rate-Xwater (mole fraction of water) profile shows that the reaction depends strongly on the medium. The fastest rate constant was obtained in pure acetone, and a minimum occurred at Xwater= 0.4, whereas the observed second-order rate constants increases again in the water-rich region. In pure acetone, in the presence of dicyclohexano-[18]-crown-6, increases linearly with the concentration of the crown ether as a result of the complexation of the sodium ion (KS = 104.8 M) of the ion-pair and the increase in the effective concentration of free 4-nitrophenoxide ion, which was assumed to be the only reactive species. Ion-pairing was also detected at Xwater= 0.65 with a dissociation constant Kd = 7.82 x 10(-4) M(-1). The solvatochromic behaviors of 2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridinio)-1-phenoxide (2), 4-[(1-methyl-4(1H)-pyridinylidene)ethylidene]-2,5-cyclohexadien-1-one (3), and 1-methyl-8-oxy-quinolinium betaine (4) were investigated in the entire range of acetone-water mixtures. The dyes presented an increasing order of hydrophili...Continue Reading

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Citations

Mar 24, 2004·Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy·Tharly BevilaquaVanderlei G Machado
Apr 29, 2005·Organic & Biomolecular Chemistry·Cristina de Garcia VenturiniClodoaldo Machado
Apr 24, 2009·Journal of the American Chemical Society·Jeffery A Byers, Timothy F Jamison
May 14, 2014·Organic Letters·Daniel R FandrickChris H Senanayake
Apr 20, 2013·The Journal of Physical Chemistry. B·Rodrigo Ormazabal-ToledoRenato Contreras
Aug 2, 2001·Journal of the American Chemical Society·D SicinskaP Paneth

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