Ultrasonic detection of hydrophobic interactions: a quantitative approach

Kinetic effects of sonication on ester hydrolysis and tert-butyl chloride solvolysis, studied in ethanol–water binary solvent, are discussed in terms of quantitative relationships between their magnitude and the hydrophobicity of reagents. A number of conclusions were drawn from the observed linear free-energy (LFE) relationships. Independent of reaction mechanism, the decrease in reaction rates with increasing ethanol content in the solvent is mainly due to hydrophobic stabilization of the ground state. While hydrophobic species can be hidden in the ethanol clusters present in the region XEtOH > 0.15, at lower ethanol contents hydrophobic reagents are weakly solvated and the hydrophobic stabilization can be easily overcome by sonication. Copyright © 2008 John Wiley & Sons, Ltd.

[1]  T. Mason,et al.  Effect of ultrasound on the solvolysis of 2-chloro-2-methylpropane in aqueous alcoholic solvents , 1987 .

[2]  S. Otto,et al.  Hydrophobic interactions and chemical reactivity. , 2003, Organic & biomolecular chemistry.

[3]  Ronald Breslow,et al.  The hydrophobic effect in reaction mechanism studies and in catalysis by artificial enzymes , 2006 .

[4]  S. Salmar,et al.  Effect of ultrasound on ester hydrolysis in aqueous ethanol. , 2001, Ultrasonics sonochemistry.

[5]  Ulf M Lindström,et al.  Stereoselective organic reactions in water. , 2002, Chemical reviews.

[6]  G. Cravotto,et al.  Effect of ultrasound on the base-catalyzed hydrolysis of 4-nitrophenyl acetate in aqueous ethanol. , 2006, The journal of physical chemistry. B.

[7]  R. Breslow,et al.  The hydrophobic effect as a mechanistic tool , 1998 .

[8]  S. Salmar,et al.  Impact of ultrasound on hydrophobic interactions in solutions: ultrasonic retardation of benzoin condensation. , 2007, Ultrasonics sonochemistry.

[9]  C. Hansch.  Quantitative approach to biochemical structure-activity relationships , 1969 .

[10]  Kenneth S. Suslick,et al.  Ultrasound: Its Chemical, Physical, and Biological Effects , 1988 .

[11]  Chao-Jun Li,et al.  Organic reactions in aqueous media with a focus on carbon-carbon bond formations: a decade update. , 2005, Chemical reviews.

[12]  A. Tuulmets.  Ultrasound and polar homogeneous reactions. , 1997, Ultrasonics sonochemistry.

[13]  Giancarlo Cravotto,et al.  Power ultrasound in organic synthesis: moving cavitational chemistry from academia to innovative and large-scale applications. , 2006, Chemical Society reviews.

[14]  Michael H. Abraham,et al.  Substitution at saturated carbon. Part 26. A complete analysis of solvent effects on initial states and transition states for the solvolysis of the t-butyl halides in terms of G, H, and S using the unified method , 1988 .

[15]  Toshiyuki Takamuku,et al.  Hydrogen-Bonded Cluster Formation and Hydrophobic Solute Association in Aqueous Solutions of Ethanol , 1995 .

[16]  T. Mason,et al.  THE EFFECT OF ULTRASOUND ON THE SOLVOLYSIS OF 2-CHLORO-2-METHYLPROPANE IN AQUEOUS ETHANOL , 1985 .

[17]  A. Fainberg,et al.  Correlation of Solvolysis Rates. IV.1 Solvent Effects on Enthalpy and Entropy of Activation for Solvolysis of t-Butyl Chloride2 , 1957 .

[18]  J. Engberts,et al.  INITIAL-STATE AND TRANSITION-STATE EFFECTS ON DIELS-ALDER REACTIONS IN WATER AND MIXED AQUEOUS SOLVENTS , 1992 .

[19]  K. Egashira,et al.  Low-Frequency Raman Spectroscopy of Ethanol−Water Binary Solution: Evidence for Self-Association of Solute and Solvent Molecules , 1998 .

[20]  Zhaoning Zhu,et al.  Quantitative Antihydrophobic Effects as Probes for Transition State Structures. 2. Diels-Alder Reactions , 1995 .

[21]  S. Salmar,et al.  Effect of ultrasound on ester hydrolysis in binary solvents , 2003 .

[22]  R. Breslow,et al.  Quantitative Antihydrophobic Effects as Probes for Transition State Structures. 1. Benzoin Condensation and Displacement Reactions , 1995 .

[23]  J. Engberts,et al.  Kinetics of hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in binary water-cosolvent mixtures; the role of solvent activity and solute-solute interactions. , 2005, Organic & biomolecular chemistry.

[24]  D. Watts,et al.  Alkaline ethanolysis of methyl 4-hydroxybenzoate and hydrolysis of methyl and ethyl 4-hydroxybenzoates in ethanol—water systems , 1985 .

[25]  A. Wakisaka,et al.  Solute-solvent and solvent-solvent interactions evaluated through clusters isolated from solutions: Preferential solvation in water-alcohol mixtures , 2001 .

[26]  Jan B. F. N. Engberts,et al.  Diels-Alder reactions in aqueous solutions. Enforced hydrophobic interactions between diene and dienophile , 1991 .

[27]  Jan B. F. N. Engberts,et al.  Hydrophobic Effects. Opinions and Facts , 1993 .

[28]  Chao-Jun Li.  Organic reactions in aqueous media - with a focus on carbon-carbon bond formation , 1993 .

[29]  Yves Queneau,et al.  Water-Promoted Organic Reactions , 1994 .