Determination of autoprotolysis constants of some non-aqueous solvents using coulometric titration

Mihajlović, R.; Simić, Zoran; Mihajlović, Lj. V.; Vukićević, Mirjana

doi:10.1016/s0039-9140(96)02000-0

“…We hypothesized that, even without the addition of acid catalysts, such minute amounts of protonated amine might be available through the auto-protolysis of the amine. Indeed, even some solvents generally regarded as aprotic or only weakly protic have been experimentally shown to auto-ionize to a limited extent (Mihajlović et al, 1996). To ascertain the likelihood of auto-protolysis of aniline and toluidines, we performed additional computations using small clusters of amine molecules, one of which was kept protonated (or deprotonated).…”

Section: Resultsmentioning

confidence: 99%

“…Solvation effects were included with the PCM formalism. Experimental values were taken from Mihajlović et al (1996).…”

Section: Discussionmentioning

confidence: 99%

New insights into the mechanism of Schiff base synthesis from aromatic amines in the absence of acid catalyst or polar solvents

Silva

¹

2020

PeerJ Organic Chemistry

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Extensive computational studies of the imine synthesis from amines and aldehydes in water have shown that the large-scale structure of water is needed to afford appropriate charge delocalization and enable sufficient transition state stabilization. These insights cannot, however, be applied to the understanding of the reaction pathway in apolar solvents due their inability to form extensive hydrogen-bonding networks. In this work, we perform the first computational studies of this reaction in nonpolar conditions. This density-functional study of the reaction of benzaldehyde with four closely related aromatic amines (aniline, o-toluidine, m-toluidine and p-toluidine) shows that, although an additional molecule of amine may provide some stabilization of the first transition state even in the absence of a hydrogen bonding network, this is insufficient to achieve high reaction rates. Our computations also show that when an extra proton is added to the spectator amine, the activation energies become so low that even picomolar amounts of protonated base are enough to achieve realistic rates. Additional computations show that those minute amounts of protonated base may be obtained under reaction conditions without the addition of extraneous acid through the auto-protolysis of the amines themselves. To our knowledge, this is the first report of a role for the auto-protolysis of anilines in their extensive reactional repertoire.

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“…We hypothesized that, even without the addition of acid catalysts, such minute amounts of protonated amine might be available through the auto-protolysis of the amine. Indeed, even some solvents generally regarded as aprotic or only weakly protic have been experimentally shown to auto-ionize to a limited extent (Mihajlović et al, 1996). To ascertain the likelihood of auto-protolysis of aniline and toluidines, we performed additional computations using small clusters of amine molecules, one of which was kept protonated (or deprotonated).…”

Section: Resultsmentioning

confidence: 99%

“…Solvation effects were included with the PCM formalism. Experimental values were taken from Mihajlović et al (1996).…”

Section: Discussionmentioning

confidence: 99%

Figure 1: Possible pathways for the reaction of aldehydes with amines.

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“…We hypothesized that, even without the addition of acid catalysts, such minute amounts of protonated amine might be available through the auto-protolysis of the amine. Indeed, even some solvents generally regarded as aprotic or only weakly protic have been experimentally shown to auto-ionize to a limited extent (Mihajlović et al, 1996). To ascertain the likelihood of auto-protolysis of aniline and toluidines, we performed additional computations using small clusters of amine molecules, one of which was kept protonated (or deprotonated).…”

Section: Resultsmentioning

confidence: 99%

Table 1: Relative free energies vs. pre-reactional complex (kcal·mol⁻¹) of the species involved in the formation of carbinolamines from benzaldehyde and aniline derivatives.

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Determination of autoprotolysis constants of some non-aqueous solvents using coulometric titration

Cited by 8 publications

References 6 publications

New insights into the mechanism of Schiff base synthesis from aromatic amines in the absence of acid catalyst or polar solvents

New insights into the mechanism of Schiff base synthesis from aromatic amines in the absence of acid catalyst or polar solvents

Figure 1: Possible pathways for the reaction of aldehydes with amines.

Table 1: Relative free energies vs. pre-reactional complex (kcal·mol⁻¹) of the species involved in the formation of carbinolamines from benzaldehyde and aniline derivatives.

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Determination of autoprotolysis constants of some non-aqueous solvents using coulometric titration

Cited by 8 publications

References 6 publications

New insights into the mechanism of Schiff base synthesis from aromatic amines in the absence of acid catalyst or polar solvents

New insights into the mechanism of Schiff base synthesis from aromatic amines in the absence of acid catalyst or polar solvents

Figure 1: Possible pathways for the reaction of aldehydes with amines.

Table 1: Relative free energies vs. pre-reactional complex (kcal·mol−1) of the species involved in the formation of carbinolamines from benzaldehyde and aniline derivatives.

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Table 1: Relative free energies vs. pre-reactional complex (kcal·mol⁻¹) of the species involved in the formation of carbinolamines from benzaldehyde and aniline derivatives.