Salt Effects and Ion Pairs in Solvolysis and Related Reactions. III.<sup>1</sup> Common Ion Rate Depression and Exchange of Anions during Acetolysis<sup>2,3</sup>

Winstein, S.; Clippinger, E.; Fainberg, Arnold H.; Heck, Richard F.; Robinson, Glenn

doi:10.1021/ja01583a022

Cited by 203 publications

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“…In order to take the role of the reaction medium more explicitly into account, Winstein and co-workers introduced the idea of stepwise dissociation of the reactant molecule (R , OH 2 ) of decreasing tightness during the S N 1 series of events. [7] Another problem is that a given set of reactants may give rise to different reaction characteristics (S N 1 or S N 2) depending on the conditions. [4,8] One way to explain this situation is to operate on a mechanistic sliding scale; no reaction is purely S N 1 or S N 2, but somewhere in-between.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Models and Experimental Data for Reactions between Water and Protonated Alcohols: Substitution and Elimination Mechanisms

Uggerud

Bache-Andreassen

1999

Chem. Eur. J.

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Section: Introductionmentioning

confidence: 99%

Theoretical Models and Experimental Data for Reactions between Water and Protonated Alcohols: Substitution and Elimination Mechanisms

Uggerud

Bache-Andreassen

1999

Chem. Eur. J.

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“…The S N 1 mechanism involves a contact ion pair (CIP) (intimate ion pair) mechanism and a solvated or dissociated free ion pair (FIP) mechanism (Scheme 1). [6] Denmark, [7] Bartlett and Heathcock, [8] and Sammakia [9] studied the mechanism of acetal substitution reactions independently. While their model systems to investigate the mechanism were different, another aspect is that they often used cyclic acetals to investigate the mech- anism, and it might be difficult to exclude the neighboring effect of the tethered oxygen atoms with Lewis acids in an intramolecular fashion.…”

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confidence: 99%

Lewis Acid‐Mediated Acetal Substitution Reactions: Mechanism and Application to Asymmetric Catalysis

et al. 2011

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Substitution reactions of acetals with carbon nucleophiles are fundamental and conventional organic reactions. We succeeded in the preparation of an optically active acetal, which reacted with a silyl enol ether smoothly to afford the desired adducts in racemic forms. By comparison of the ees of the products with the ees of the recovered acetals, we concluded that the aldol-type reactions proceeded not via direct displacement (S N 2) or contact ion pairs (intimate ion pair) (S N 1) but by a free oxocarbenium ion (S N 1) mechanism. Next, a study to achieve asymmetric catalysis of the acetal substitution reactions was conducted. After many trials, it was found that a chiral niobium complex prepared from pentamethoxyniobium [NbA C H T U N G T R E N N U N G (OMe) 5 ] and a tetradentate BINOL derivative could achieve high enantioselectivities. Asymmetric aldol-type reactions of acetals with silyl enol ethers proceeded smoothly to afford the corresponding aldol-type adducts in good yields with high enantioselectivities.

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“…[32][33][34][35][36][37] We examined the effects of salts on the isomerization reaction of β-PMo12 into α-PMo12 for a 50 mM (Table 2). Next, the effect of the type of cation on the isomerization reaction was examined by using a chloride salt of various metal cations, such as Na + , K + , Mg 2+ and Ca 2+ .…”

Section: Effects Of Salts On the Isomerization Reaction Of β-Pmo12 Inmentioning

confidence: 99%

Effects of Organic Solvents and Salts on the Isomerization Reaction (β→α) of Keggin-type 12-Molybdophosphate Anion

Ueda

Isai

2013

ANAL. SCI.

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Experimental Reagents and chemicalsAll of the chemicals were of analytical grade, and were used without further purification. Mo(VI) and P(V) stock solutions were prepared from Na2MoO4·2H2O and NaH2PO4·2H2O, The isomerization reaction of the β-form of 12-molybdophosphate ([PMo12O40] 3-: PMo12) into the α-form in aqueous-organic mixed media containing various salts was extensively investigated with cyclic voltammetry. It was found that the concentration and type of organic solvent and salt strongly affected the rate of the isomerization reaction. When organic solvents with lower permittivity than water were used as auxiliary solvents, and high concentrations of salts were added to the reaction mixture, the β-form of PMo12 (β-PMo12) became more stable, leading to slow isomerization into the α-form (α-PMo12). Based on the results of this study, it is proposed that the isomerization reaction of β-PMo12 into α-PMo12 is caused by the attack of a proton on a corner-shared oxygen atom. Also, the variation of its reaction rate upon the addition of organic solvents and salts is due to interactions between both the protons and the solvents or anions, and between the cations and the PMo12 anion.

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Salt Effects and Ion Pairs in Solvolysis and Related Reactions. III.¹ Common Ion Rate Depression and Exchange of Anions during Acetolysis^2,3

Cited by 203 publications

References 0 publications

Theoretical Models and Experimental Data for Reactions between Water and Protonated Alcohols: Substitution and Elimination Mechanisms

Theoretical Models and Experimental Data for Reactions between Water and Protonated Alcohols: Substitution and Elimination Mechanisms

Lewis Acid‐Mediated Acetal Substitution Reactions: Mechanism and Application to Asymmetric Catalysis

Effects of Organic Solvents and Salts on the Isomerization Reaction (β→α) of Keggin-type 12-Molybdophosphate Anion

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Salt Effects and Ion Pairs in Solvolysis and Related Reactions. III.1 Common Ion Rate Depression and Exchange of Anions during Acetolysis2,3

Cited by 203 publications

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Theoretical Models and Experimental Data for Reactions between Water and Protonated Alcohols: Substitution and Elimination Mechanisms

Theoretical Models and Experimental Data for Reactions between Water and Protonated Alcohols: Substitution and Elimination Mechanisms

Lewis Acid‐Mediated Acetal Substitution Reactions: Mechanism and Application to Asymmetric Catalysis

Effects of Organic Solvents and Salts on the Isomerization Reaction (β→α) of Keggin-type 12-Molybdophosphate Anion

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Salt Effects and Ion Pairs in Solvolysis and Related Reactions. III.¹ Common Ion Rate Depression and Exchange of Anions during Acetolysis^2,3