Lactic acid dissociation constants

P a negative logarithm of the acid dissociation constant PLA poly(lactic acid)... 

Fig. 19.7. Relationship between acid dissociation constant pK and frequency (v) of the antisymmetric stretching vibration of salts of carboxylic acids in DjO solution. 1, Trifluoroacetic 2, trichloroacetic 3, dichloroacetic 4, cyanoacetic 5, chloroacetic 6, 2-phenoxypropionic 7, methoxyacetic 8, formic 9, glycollic 10, lactic 11, 3-hydroxybutyric 12, acetic 13, propionic 14,cyclohexane carboxylic 15, polyacrylic 16, malonic 17, phthalic 18, benzoic 19, salicylic and 20. polyguluronic. polygalacturonic, galacturonic, alginic, hyaluronic, and chondroitin sulfates A, B, and C. ( C) From Goulden and Scott, 1968 (O) from Chapman et at. 1964. The pK values are from references given in Goulden and Scott (1968). (Goulden and Scott, 1968.)...

Lactic acid, CH3CH(OH)COOH, received its name because it is present in sour milk as a product of bacterial action. It is also responsible for the soreness in muscles after vigorous exercise, (a) The pfQ, of lactic acid is 3.85. Compare this with the value for propionic acid (CH3CH2COOH, pfC = 4.89), and explain the difference. (b) Calculate the lactate ion concentration in a 0.050 M solution of lactic acid, (c) When a solution of sodium lactate, (CH3CH(OH)COO)Na, is mixed with an aqueous copper(II) solution, it is possible to obtain a solid salt of copper(II) lactate as a blue-green hydrate, (CH3CH(0H)C00)2 Cu-a H20- Elemental analysis of the solid tells us that the solid is 22.9% Cu and 26.0% C by mass. What is the value for x in the formula for the hydrate (d) The acid-dissociation constant for the Cu (aq) ion is 1.0 X 10. Based on this value and the acid-dissociation constant of lactic add, predict whether a solution of copper(Il) lactate will he addic, basic, or neutral. Explain your answer. 

Of the two major weak organic acids produced by LAB (acetic and lactic acid), acetic acid is the strongest inhibitor because of its higher dissociation constant (pKa = 4.75) as compared to lactic acid (pKa = 3.08) at a given molar concentration and pH level (Eklund, 1983 Holzapfel et al., 1995 Ouwehand, 1998). 

The transport of hydrogen ions out of the cell is also important for maintenance of a constant intracellular pH. Metabolism produces a number of other acids in addition to CO2. For example, the metabolic acids acetoacetic acid and (3-hydroxybutyric acid are produced from fatty acid oxidation to ketone bodies in the liver, and lactic acid is produced by glycolysis in muscle and other tissues. The pKa for most metabolic carboxylic acids is below 5, so these acids are completely dissociated at the pH of blood and cellular fluid. Metabolic anions are transported out of the cell together with H (see Fig. 4.9, circle 8). If the cell becomes too acidic, more H is transported out in exchange for Na ions by a different transporter. If the cell becomes too alkaline, more bicarbonate is transported out in exchange for Cl ions. 

J. Partanen, P. Juusola and P. Minkkinen, Determination of stoichiometric dissociation constants of lactic acid in aqueous salt solutions at 291.15 and 298.15 K, Fluid Phase Equilib., 2003, 204, 245-266. 

The effect of exchange of lactic, mandelic and sulfosalicylic acids on the relaxation of solvent protons gave rate constants (k) of exchange from 1.73 to 0.701 mol-1 s-1.642 Kinetics of complex formation with mandelic (HMDA) and vanillomandelic acids (HVMDA) gave rate constants (1.09 x 103 and 1.13 x 103 mol-1 s 1 for MDA- and VMDA ) consistent with a dissociative (Eigen) mechanism.438 As in the case of oxalic and malonic acids (Section 33.5.5.5.ii Table 27), species with coordinated hydroxyl are labilized. 

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