title: (Thio)urea organocatalyst equilibrium acidities in DMSO.
abstract: Bordwell's method of overlapping indicators was used to determine the pK(a) values of some of the most popular (thio)urea organocatalysts via UV spectrophotometric titrations. The incremental effect of CF(3) groups on acidic strength was also investigated. The pK(a)'s are in the range of 8.5-19.6. The results may lead to a better understanding of noncovalent organocatalysis and may aid in future catalyst development.
authors.affiliation: Institute of Organic Chemistry, Justus-Liebig University Giessen, Heinrich-Buff-Ring 58, 35392 Giessen, Germany.
authors.forename: Gergely
authors.initials: G
authors.lastname: Jakab
authors.forename: Carlo
authors.initials: C
authors.lastname: Tancon
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Zhang
authors.forename: Katharina M
authors.initials: KM
authors.lastname: Lippert
authors.forename: Peter R
authors.initials: PR
authors.lastname: Schreiner