Nucleophilic addition to olefins. Kinetics and mechanism

Kinetics and Mechanism of Triethylamine Catalysed Michael Addition of Benzenethiol to 1-(2-Nitrovinyl)benzene in Acetonitrile

“…6 The mode of rate variation with para-substituted benzenethiols in the addition reactions is opposite to the general behaviour observed in nucleophilic addition reactions of neutral nucleophiles with activated olefinic bonds. [1][2][3][4][5] In all these cases ρ x is observed to be negative. A larger negative value of ρ x is observed in the addition of benzylamine to 1-(2-nitrovinyl)benzene in acetonitrile 4a and also in the addition of benzenethiols to 4'-[N-(9-Acridinyl)]-1'-(N-methanesulfonyl)-3'-methoxyquinine diimide.…”

“…In aqueous medium the reaction proceeds through the formation of zwitterion with charge imbalanced transition state. 1 It is observed that even though the reactions show typical behaviour of a carbanion forming process, the carbanion is largely stabilized by the polar effects while resonance effects playing a more modest role. 2 On the other hand, the nucleophilic addition of amines to activated olefins in acetonitrile 4 shows that proton transfer to β-carbon and N-C α bond formation occur concertedly and the neutral adducts are formed in a single step but not through zwitterion formation.…”

“…[1][2][3][4][5] The activating groups are normally electron acceptors which act to stabilize the intermediate carbanion in the stepwise pathway. 1 The addition reactions of amine nucleophiles to olefins containing activating groups have been investigated. 3 In these reactions, solvent plays an important role on the mechanism.…”

Reactions of substituted benzylidene Meldrum’s acids and methylthiobenzylidene Meldrum’s acids with OH–, CF3CH2O– And HOCH2CH2S– in 50% DMSO-50% water. π-Donor effects, soft acid-base interactions and transition state imbalances

“…[15][16][17] Another is imbalanced transition states in the sense that charge delocalization into X,Y lags behind bond formation between carbon and the nucleophiles. [15][16][17] What complicates the reactivity patterns is that other factors such as the π-donor ability of Nevertheless, there is an accumulating database that confirms the expected correlation between intrinsic barriers and π-acceptor strength for these reactions but there is only a relatively small number of investigations that address the question of transition state imbalance. Information about the latter comes from the study of substituent effects that provide Brønsted-type structurereactivity coefficients such as α nuc n = dlog k 1 …”

Kinetic Study on Michael-type Reactions of 1-Phenyl-2-propyn-1-one with Alicyclic Secondary Amines: Effect of Medium on Reactivity and Mechanism

“…These reactions have been reported to proceed through either a concerted or a stepwise mechanism. [1][2][3][4] The corresponding reactions of carbon-carbon triple bonds conjugated with a strong EWG have also been studied widely. [5][6][7][8][9][10][11][12] However, most studies have been focused on the stereochemistry of the reaction products (e.g., Z-or Eisomer) due to synthetic interests.…”