Nucleophilicities and Carbon Basicities of Pyridines

Brotzel, Frank; Kempf, Bernhard; Singer, Thomas P.; Zipse, Hendrik; Mayr, Herbert

doi:10.1002/chem.200600941

Cited by 135 publications

(108 citation statements)

References 75 publications

(38 reference statements)

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“…[7] Previous results obtained computationally in gas phase and in ethanol at MP2(fc)/6-31G(d) level of theory (solvent polarizable continuum model) showed that the positive charge in the reactant ground state of benzhydrylpyridinium ions is distributed between the nitrogen atom and the methine carbon atom in a way that only 66 % of the positive charge is located on the nitrogen atom. [13] It has also been shown that the charge distribution is almost invariant of the substituents on the benzhydryl group or pyridine moiety. This observation is completely different from that obtained with sulfonium salts (tetrahydrothiophenium and dimethylsulfonium) in which the positive charge is almost completely located on the leaving group.…”

Section: Pyridinium Saltsmentioning

confidence: 99%

“…Because of the invariant charge distribution of the partial charges in the reactant ground state of beznhydrylpyridinium salts with changing electrofugality, [13] it can be approximated that the stabilizations by solvation in all the reactant ground states are similar. Thus, solvent effects of pyridinium salts come from different solvation of the transition state.…”

Section: Pyridinium Saltsmentioning

confidence: 99%

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Nucleofugalities of Neutral Leaving Groups in 80 % Aqueous Acetonitrile

Jurić¹,

Portolan²,

Kronja³

2016

Croat. Chem. Acta

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Nucleofugalites of tetrahydrothiophene, dimethyl sulfide and differently substituted pyridines in 80 % aqueous acetonitrile have been derived from the SN1 solvolysis rate constants of the corresponding X,Y-substituted benzhydryl derivatives (1-10). In solvolysis of sulfonium ions in 80 % aqueous acetonitrile, where acetonitrile is a good cation solvator, the solvation of the reactant ground state is an important rate determining variable since the positive charge is almost entirely located on the leaving group. As a consequence, reaction rates of sulfonium ions are more sensitive to the substrate structure in 80 % aqueous acetonitrile than in pure and aqueous alcohols, which are less efficient as cation solvators. In solvolysis of pyridinium ions the solvation of the reactant ground state is less important, since the positive charge is considerably distributed between the carbon at the reaction center and the leaving group. In such cases the important rate determining variable is solvation of the transition state. Slower reactions of pyridinium substrates progress over later, carbocation-like transition states in which the solvation is more important, so those substrates solvolyze slightly faster in aqueous acetonitrile than in methanol (k80AN > kM). Faster reactions proceed over earlier TS in which the solvation is diminished, so those substrates solvolyze somewhat faster in methanol than in aqueous acetonitrile (k80AN < kM).

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Section: Pyridinium Saltsmentioning

confidence: 99%

Section: Pyridinium Saltsmentioning

confidence: 99%

Nucleofugalities of Neutral Leaving Groups in 80 % Aqueous Acetonitrile

Jurić¹,

Portolan²,

Kronja³

2016

Croat. Chem. Acta

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“…Recent determination of nucleophilicity parameters for these two pyridines identified a large solvent effect, leading to higher nucleophilicities for PPY than for DMAP in dichloromethane, but to the reverse order in protic solvents such as H 2 O. [23] The combined presence of t-BuOH and acidic substrates may lead to a similar reduction of the intrinsically higher nucleophilic activity of PPY in this case. It should be added that the reaction proceeds extremely slowly in the absence of any of the pyridine bases (but with 2 equiv.…”

Section: Resultsmentioning

confidence: 96%

Domino Catalysis in the Direct Conversion of Carboxylic Acids to Esters

et al. 2008

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“…The limitations of Equations (1) and (2) will be illustrated below by correlations of kinetic data for reactions of benzhydrylium cations 1 and 2 [18][19][20][21] and for the methylvinylpyridinium cation 3.…”

mentioning

confidence: 99%

Limitations of the s(E+N) and Related Equations: Solvent Dependence of Electrophilicity

Bentley

2011

Angewandte Chemie

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electrophilicity · kinetics · linear free-energy relationships · nucleophilicity · solvent effects Generic expressions that capture the essence of reactivity patterns still have important roles, despite the huge advances in computational chemistry for individual systems.[1, 2] New generic equations are relatively rare, and critical scrutiny of the scope and reliability of two such equations [Eqs. (1) and (2)] is presented below. log k ¼ s ðE þ NÞ, or changing the symbol for sThe s(E+N) equation [Eq.(1)] has been developed empirically from constant selectivity relationships [3,4] to correlate logarithms of rate constants (log k) at 208C for a huge range of reactions of electrophiles (electrophilicity E) and nucleophiles (nucleophilicity N); in Equation (1), s (or s N ) [5][6][7] is referred to as a "nucleophile-specific" parameter, [7] and in Equation (2), s E is an "electrophile-specific" parameter.

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Nucleophilicities and Carbon Basicities of Pyridines

Cited by 135 publications

References 75 publications

Nucleofugalities of Neutral Leaving Groups in 80 % Aqueous Acetonitrile

Nucleofugalities of Neutral Leaving Groups in 80 % Aqueous Acetonitrile

Domino Catalysis in the Direct Conversion of Carboxylic Acids to Esters

Limitations of the s(E+N) and Related Equations: Solvent Dependence of Electrophilicity

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