Reactivity of sodium arenesulfinates in the substitution reaction to γ‐functionalized allyl bromides

Abstract

The kinetics of nucleophilic bimolecular substitution reactions of γ‐functionalized allyl bromides with non‐substituted and p‐substituted sodium arenesulfinates has been studied. Both the structure of allyl bromides and nucleophilicity of arenesulfinate ions exerted a significant effect on the values of the kinetic parameters such as the second‐order rate constants k, activation energy EA, and changes in the entropy ΔS≠, enthalpy ΔH≠, and free energy ΔG≠ of the formation of the activated complex from reactants. Based on the evaluation of kinetic parameters, the reactants could be arranged, according to their decreasing reactivity in the SN2‐reactions as follows: p‐toluenesulfinate ion > benzenesulfinate ion > p‐chlorobenzenesulfinate ion and 4‐bromo‐2‐butenenitrile > 1,3‐ dibromopropene, respectively. Comparison was also made between the kinetic data obtained and some delocalization reactivity indexes for both the substrates and nucleophiles. The enthalpy–entropy compensation effect was observed for the reactions of sodium arenesulfinates with γ‐functionalized allyl bromides. Copyright © 2009 John Wiley & Sons, Ltd.

Towards mechanisms of bimolecular nucleophilic reactions in solution—probing the variation of the activation parameters in the reactions of aromatic compounds

“…The deviations for the reactions of entries 31 and 32 in Table , possibly, can be explained by a distorted structure of trigonal–bipyramidal TS 3 in S N 2–b reactions (Schemes and ).The Br–C–S angle deviates from 180°, and a longer C–S bond leads to an increase in the δ Δ S ≠ values on passing to electron‐withdrawing substituents ( cf . Reference ).…”

“…From temperature‐dependent rate data, the Eyring plots were generated by plotting log( k / T ) versus 1/ T , and the enthalpy and entropy of activation, Δ H ≠ and ΔS ≠ , were determined for the reactions of alkyl‐ 1 , 2 , alkenyl‐ 3 and alkynyl sulfonates 4 , N ‐methyl pyridines 5 , alkyl halides 6 , 12 , esters 14 , 15 , 16 , 17 , 18 , acyl chlorides 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , amides 28 , 29 , anhydride 30 , substituted 2‐chloro pyridines 31 , 32 , aryl halides 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , substituted ethylenes 45 , 46 , 47 , and acetylene 48 with charged 53 , 57 , 58 , 59 , 63 , 64 , 65 , 66 , 70 , 71 , 72 , and uncharged nucleophiles 49 52 , 54 , 55 , 56 , 61 , 62 , 68 , 69 , and 73 (Scheme ). The Δ H ≠ , ΔS ≠ , and ΔG ≠ activation parameters obtained were used by Eqns to establish the δ Δ H ≠ , δ ΔS ≠ , and δΔG ≠ reaction constants (Table and Tables 1S–3S in the Supporting Information).…”

Activation parameter changes as a mechanistic tool in SN2 reactions in solution

“…The large magnitudes of δΔG ≠ in comparison with the δΔН ≠ int values for the reactions of entries 6 and 7 in Table 3 can be explained by the formation of the distorted trigonalbipyramidal TS-8 [27]. The Br-C-S angle deviates from 180 degrees and the longer C -S bond leads to an increase of the δΔS ≠ values (entries 41 and 42 in Table 1) on passing to the electron-withdrawing substituent R in nucleophile (Scheme 6) [67].…”

“…The lines II and III from Figure 1 combine a relatively fast reactions [50,[53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] and the compensation relationships for these lines are tested at a confidence level of >95% [27,43]. The slopes of the lines II and III correspond to compensation temperatures Tcomp equaling 380 and 370 K, respectively.…”