Mechanism for the Oxidation of Sulfides and Sulfoxides with Periodates: Reactivity of the Oxidizing Species

Abstract

DFT computations have been performed at different levels of theory to identify the mechanism for the oxidation of sulfides and sulfoxides with periodates. The periodate ion (IO 4 -), periodic acid (HIO 4 ) and their hydrated derivatives all oxidize sulfides to sulfoxides in one-step oxygen-transfer reactions and the relative reactivities are HIO 4 ϾϾ H 5 IO 6 Ͼ IO 4 -Ͼ H 4 IO 6 -ϾϾ H 3 IO 6 2-. The hydration and dissociation equilibria of the periodates are shifted towards IO 4 -in neutral and moderately acidic solutions, and sulfides are oxidized mainly with IO 4 -under normal experimental conditions. The oxygen atoms of the periodates attack the sulfides perpendicularly to the plane of the C-S-C atoms and the S···O···I atoms are in a linear arrangement in the very early transition state (TS). The sulfides are the electron donors and periodates are the

Concerted SN2 mechanism for the hydrolysis of acid chlorides: comparisons of reactivities calculated by the density functional theory with experimental data

“…Summing up the results, obtained in this and in our earlier papers35–39 concerning the structure of the TSs in S N 2 nucleophilic substitutions, we can conclude that early TSs are formed if the attacking reagent is better, and late TSs are formed if the attacking reagent is poorer nucleophile than the leaving group. On the other hand, loose TSs are formed if e‐d, and tight TSs are formed if e‐w substituents are bonded to the substrates.…”

“…The computed and experimentally derived activation parameters were correlated with the Hammett substituent constants, as described previously35–39 (Eqn 3, P = E , G , H or S ). …”

“…Earlier we have performed DFT calculations on aliphatic S N 2 and S N 1 nucleophilic substitutions 35–39. The medium effect on reactivity was computed using the polarizable continuum model (PCM) of solvents (see Section Computational methods).…”

Oxidation of Methionine Residues in Polypeptide Ions Via Gas-Phase Ion/Ion Chemistry

“…A second pathway is outlined in Scheme 2 and results in covalent modification of the methionine residue to produce the oxidized species, [M+H+O] + . [42,43] The latter species is also observed in Figure 1(a) and arises from collisional activation of the complex upon transfer from the reaction cell to Q3. The generation of [M+H+O] + ions from collisional activation of the complex has been observed to be the favored pathway for methionine-containing peptides (see Figure 1(b)).…”

Halogens

“…55 Efficient continuous flow micro-reactor technology has been developed for the high yield epoxidation of alkenes with HOFÁCH 3 CN. 57 The chemistry of atmospheric chlorine oxides continues to garner great theoretical interest. 57 The chemistry of atmospheric chlorine oxides continues to garner great theoretical interest.…”