title: Impact of ultrasound on hydrophobic interactions in solutions: ultrasonic retardation of benzoin condensation.
abstract: Kinetics of the benzoin condensation of benzaldehyde in presence of KCN as the catalyst in water and in ethanol-water binary solutions were investigated without sonication and under ultrasound at 22 kHz. A statistically significant 20% decrease of the rate was observed in water. The retardation effect of ultrasound gradually decreases up to 45 wt% ethanol content. We report an evidence of ultrasonic retardation of reactions and thereby a direct evidence for sonochemical processes in the bulk solution. Ultrasound can disturb solvation of the species in the solution. If breaking down the stabilization of the encounter complexes between the reagents, sonication hinders the reaction while perturbation of the solvent-stabilization of the reagents accelerates the reaction.
authors.affiliation: Institute of Organic and Bioorganic Chemistry, University of Tartu, 2 Jakobi Street, 51014 Tartu, Estonia.
authors.forename: Hannes
authors.initials: H
authors.lastname: Hagu
authors.forename: Siim
authors.initials: S
authors.lastname: Salmar
authors.forename: Ants
authors.initials: A
authors.lastname: Tuulmets
mesh_terms: D001573:Benzoin / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D012996:Solutions; D014465:Ultrasonics
chemical_list: D012996:Solutions; D001573:Benzoin