Read e-book online Acids and Bases: Solvent Effects on Acid-Base Strength PDF

By Brian G. Cox

ISBN-10: 019967051X

ISBN-13: 9780199670512

Acids and bases are ubiquitous in chemistry. Our knowing of them, notwithstanding, is ruled by way of their behaviour in water. move to non-aqueous solvents results in profound adjustments in acid-base strengths and to the charges and equilibria of many procedures: for instance, artificial reactions regarding acids, bases and nucleophiles; isolation of pharmaceutical actives via salt formation; formation of zwitter- ions in amino acids; and chromatographic separation of substrates. This booklet seeks to reinforce our knowing of acids and bases by way of reviewing and analysing their behaviour in non-aqueous solvents. The behaviour is expounded the place attainable to that during water, yet correlations and contrasts among solvents also are presented.

Fundamental heritage fabric is equipped within the preliminary chapters: quantitative points of acid-base equilibria, together with definitions and relationships among answer pH and species distribution; the impression of molecular constitution on acid strengths; and acidity in aqueous resolution. Solvent houses are reviewed, besides the significance of the interplay energies of solvent molecules with (especially) ions; the power of solvents to take part in hydrogen bonding and to just accept or donate electron pairs is obvious to be the most important. Experimental tools for picking dissociation constants are defined in detail.

In the remainder chapters, dissociation constants of quite a lot of acids in 3 targeted periods of solvents are mentioned: protic solvents, similar to alcohols, that are powerful hydrogen-bond donors; uncomplicated, polar aprotic solvents, resembling dimethylformamide; and low-basicity and occasional polarity solvents, akin to acetonitrile and tetrahydrofuran. Dissociation constants of person acids fluctuate over greater than 20 orders of significance one of the solvents, and there's a robust differentiation among the reaction of impartial and charged acids to solvent switch. Ion-pairing and hydrogen-bonding equilibria, resembling among phenol and phenoxide ions, play an more and more vital function because the solvent polarity decreases, and their impact on acid-base equilibria and salt formation is defined.

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Additional info for Acids and Bases: Solvent Effects on Acid-Base Strength

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1980, 9, 381 [13] Butler, J. , Cogley, D. , Grunwald, E. J. Phys. , 1971, 75, 1477 [14] Chantooni, M. , Kolthoff, I. M. J. Phys. , 1973, 77, 527 Determination of Dissociation Constants 4 Methods of determining dissociation constants in aqueous solution are well established, and analogous methods are also used in non-aqueous media. They are mostly based on the measurement of pH in solutions of known acid and base concentrations, or measurement of the ratios of acid and base in solutions of fixed pH.

Handbook of Proton Ionization Heats and Related Thermodynamic Quantities’, Wiley-Interscience, 1976 [5] Perrin, D. , Serjeant, E. P. ‘pKa Predictions for Organic Acids and Bases’, Chapman & Hall, 1981 [6] Bell, R. P. ‘The Proton in Chemistry’, Chapman and Hall, 1973 [7] Stewart, R. ‘The Proton: Applications to Organic Chemistry’, Academic Press, NY, 1985 [8] Bordwell, F. , Branca, J. , Hughes, D. , Olmstead, W. N. J. Org. Chem. 1980, 45, 3305 [9] Amyes, T. , Richard, J. P. J. Am. Chem. , 1996, 118, 3129 [10] Grabowski, J.

4) gives eq. 4) Successive substituting for the various species from eqs. 3) in terms of [H+ ] into eq. 4) gives eqs. * etc. 7) Extension of eqs. 7) to cover the general case of acid Hn A is obvious. Provided the various pKa are known, eqs. 7) and their analogues for other acids, Hn A, can be used in conjunction with a simple spreadsheet to calculate the pH-dependence of the species distribution. References [1] Bell, R. P. ‘Acids and Bases: Their Quantitative Behaviour’, Methuen, 1971 [2] Atherton, J.

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Acids and Bases: Solvent Effects on Acid-Base Strength by Brian G. Cox


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