p<i>K</i>_a Determination of Strongly Acidic C-H Acids Bearing a (Perfluoroalkyl)sulfonyl Group in Acetonitrile by Means of Voltammetric Reduction of Quinone

Abstract

A voltammetric method has been developed for the determination of the acid dissociation constant (pK a) of (RfSO 2) 2 CHR (Rf = perfluoroalkyl), which is a strongly acidic molecule that serves as an acid catalyst. In acetonitrile solution containing small quantity of the acid, the reduction peak potential of quinone caused by the acid shifted to a more positive side accompanied by an increase in the acidity of the acid. This relationship was in good agreement with an equation derived from the Nernst equation. The present finding has been successfully applied to the determination of the pK a of the acids in acetonitrile with values ranging from 7 to 17.

Determination of Amino Acidity in Japanese Sake Based on the Voltammetric Measurement of Surplus Acid by Quinone Reduction

“…Although the ill-defined prepeak of DBBQ caused by the succinic acid appeared at -0.32 V vs. Ag/AgCl, the prepeak heights of DBBQ caused by the HCl were almost the same without and with succinic acid. Because the appearance of a prepeak potential of quinone is dependent on the acidity of compounds, 20 it is expected that a proton of succinic acid is not donated to the reduction of DBBQ at a potential where the prepeak of DBBQ caused by HCl appears. Considering the definition of amino acidity in Japanese sake, amino acidity, V, is expressed as follows:…”

Ethene‐1,1‐disulfonyl Difluoride (EDSF) for SuFEx Click Chemistry: Synthesis of SuFExable 1,1‐Bissulfonylfluoride Substituted Cyclobutene Hubs

“…Our approach involved heating methanedisulfonyl fluoride (MDSF) with paraformaldehyde and a range of 2‐substituted pyridines, such as 2,4‐dimethyl‐, 2‐acetyl‐, 2‐fluoro‐, 2‐chloro‐, and 2‐bromopyridine, along with pyridine in anhydrous DCE [39] . While the reactions involving 2‐substituted pyridines resulted in complex product mixtures, [40] the reaction with pyridine successfully yielded 1,1‐bis(fluorosulfonyl)‐2‐(pyridin‐1‐ium‐1‐yl)ethan‐1‐ide ( 3 ) as a bench‐stable precursor. This precursor was obtained in gram‐scale quantities (2.4 g) within a short reaction time of 1 h (Scheme 1A) [41, 42]…”

Development of Stable Carbanionic Substituents

“…With several compounds in our hands, the p K a values in acetonitrile were measured using the voltametric method (Figure 8). [22] In this medium, Tf 2 CH 2 1 a (10.4) was a stronger acid than the C ‐methylated derivative 11 a (14.0), but a weaker acid than the C ‐phenylated derivative 11 d (7.85) [5] . Although the replacement of the trifluoromethyl groups in 1 a to nonafluorobutyl groups enhanced the acidity by −1.4 p K a unit, cyclic derivative 1 c (11.3) showed slightly weaker acidity than 1 a .…”