Related Experiment Video
Updated: Sep 16, 2025

Hot Biological Catalysis: Isothermal Titration Calorimetry to Characterize Enzymatic Reactions
Published on: April 4, 2014
Determination of the pK aH of Established Isothiourea Catalysts
Lukas S Vogl1, Matthias Bechmann1, Mario Waser1
1Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz, Austria.
Abstract:
Isothioureas (ITUs) represent a powerful family of (chiral) Lewis base organocatalysts. Interestingly, the Brønsted basicity of these frequently used compounds has so far not systematically been investigated. Thus, we have now determined the pK aH values of the most privileged (chiral) ITUs in acetonitrile (ACN) and DMSO by using NMR. Employing Wallace's chemical shift imaging NMR method, the herein investigated ITUs were found to be weak Brønsted bases with pK aH values in the range of 16.8-17.9 in ACN and 6.3-7.8 in DMSO.
More Related Videos
12:08Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes
Published on: June 24, 2022
10:19Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation
Published on: July 18, 2017
Related Concept Videos
Arrhenius Plots
The Arrhenius equation can be used...
Titration of a Polyprotic Acid
Calculating the Equilibrium Constant
For example, gaseous nitrogen dioxide forms dinitrogen tetroxide according to this equation:
Factors Affecting α-Alkylation of Ketones: Choice of Base
The reaction involving bases like EtO− whose conjugate acid EtOH (pKa = 15.9) is stronger than the ketone (pKa = 19.2) results in an equilibrium mixture with higher ketone concentration. As a consequence,...
Titration of Polyprotic Acids with a Strong Base