Effects of sulfenyl, sulfinyl and sulfonyl groups on acidities and homolytic bond dissociation energies of adjacent C?H and N?H bonds

Abstract

Acidities and bond dissociation energies (BDEs) of the N-H bond in two phenylsulfenylamides, PhSNHBz and PhSNH-t-Bu, and four phenylsulfenylanilides, 4-GC 6 H 4 NHSPh, where G = MeO, H, Br and CN, were measured in order to compare the effects of substituents on acidities and BDEs of N-H bonds with those of C-H bonds. The effects of PhS groups on acidities and BDEs in a series of C-H acids were found to be comparable to those on acidities and BDEs of PhS in a similar series of N-H acids. Comparisons were also made of the effects of changing the oxidation state of sulfur in the series PhS, PhSO

Impact of sulfur substituents on the C–H⋯O interaction of terminal alkynes in crystal engineering

“…The influence of the sulfoxide functional group is entirely different in this case, with one of the aromatic hydrogen atoms ortho to the ethynyl group, rather than one of the methyl hydrogen atoms, involved in the hydrogen bonding interaction; in a similar fashion to a recent report by Cardellicchio et al 16 The result is a C(6) chain in zig-zag fashion along the b-axis. The combination of the two hydrogen bonds generates three molecule R 2 3 (13) rings between neighbouring chains. The overall structure can be described as pairs of chains giving rise to a ''slipped'' ladder motif in the (102) plane (Fig.…”

“…1 H NMR spectra were recorded at 300 MHz on a Bruker Avance 300 spectrometer. 13 C NMR spectra were recorded on a Bruker Avance 300 spectrometer at 75 MHz.…”

“…Comparison of analogous structures bearing either the sulfoxide or sulfone functionality allows the influence of the oxidation state of the sulfur atom to be investigated, as well as varying the number of potential hydrogen bond acceptors. In addition, as increasing the oxidation state of the sulfur atom increases the acidity of a-hydrogens, 13 this allows the a C-H moiety to act as potential hydrogen bond donor. On the basis of their relative acidities, the a C-H in the sulfoxides or sulfones may be envisaged to compete with the terminal alkyne as hydrogen bond donors.…”

The effects of hydrogen bonds on metal-mediated O2 activation and related processes

“…18 In addition, [Mn IV H 3 buea(O)] À can react with substrates having BDE CÀH of 490 kcal mol À1 , an example of which is DMSO (BDE CÀH , 94 kcal mol À1 ). 19 Additional reactivity studies showed that O-atom transfer was possible from [Mn IV H 3 buea(O)] À : treating [Mn IV H 3 buea(O)] À with PMePh 2 in DMSO at room temperature or at À45 1C in DMF produced OQPMePh 2 in B60% yield. Moreover, 18 OQPMePh 2 (B50% yield) was produced when the reaction was carried out with [Mn IV H 3 buea( 18 O)] À , proving that the Mn IV -oxo complex was the oxidant.…”

Control of proton concentration in water and organic solvents using electrochemically generated acid in very small footprint electrochemical cells.

“…These tables were created mainly by the spectrophotometric titration of the acids to determine its acidity relative to some indicator acid, whose conjugate anion was colored. [7][8][9][10][11][12][13][14][15] After Bordwell's work, other contributions completed the information with data relative to pKa values in other solvents obtained from different experiments including UV-vis measurements 16,17 , potentiometry [18][19][20] , quantum chemistry [21][22][23] , magnetic nuclear resonance 24 and other indirect measurements of the relative acidity and basicity of the compounds. For practical reasons, potentiometric acidity sensors like glass electrodes or ISFETs are the most used pH meters in water [25][26][27][28] .…”