K and pK

We consider a fractal arterial tree that consists of several branching levels where each level consists of parallel vessels, Figure 8.5 A. Each vessel is connected to m vessels of the consequent branching level [322]. We make the assumption that the vessel radii and lengths at each level k follow a distribution around the mean values f)k and pk, respectively. The variance of the vessel radii and lengths at each level produces heterogeneity in the velocities. 

Hashida et al. also found a good linear relationship for the azo coupling rates of 11 P-dicarbonyl compounds and the pK values of these C-acids. However, two dicarbonyl compounds with a trifluoromethyl group attached to one of the carbonyl functions were exceptions. Furthermore, no relationship between log k and pK could be observed for azo coupling reactions of active methylene compounds other than p-dicarbonyls. 

Consult Appendices IV and VII for K, and pK values. Answers to the Practice Problems are given on pages 421-423. 

Strong acids have low pK values weak acids have high pK values. For example, formic acid is moderately strong pfC = 3.75. The pK values for other adds and proton-donating compoimds are phosphoric acid (H3PO4), 2.14 acetic acid (CH3COOH), 4.76 carbonic acid (H2CO3), 3.8 ammonium ion (NH ), 9.25 and bicarbonate ion (HCOj), 10.2. The values for K and pK refer to reactions that are reversible in aqueous solution and have attained a condition of equilibrium. 

Another kind of dissimilarities both from simple liquids and a binary mixtures of neutral particles is caused by the factor B(k = 0) = Bo. Let us use the results obtained above for deriving the last two hydrodynamic equations [see (41) and (42)], describing the longitudinal dynamics of the model in small k limit. It can be done directly from the Eqs. (46) and (47), taking into account the existing relations between two subsets of dynamic variables, describing the density fluctuations, namely, pk, i k and pk, 7k [see Eq. (51)]. In small k... 

Note that a larger K value corresponds to a smaller p a ) A selection of K and pK values is given in Table 1. If pAa<0 (i.e. >1) the equilibrium lies strongly to the right, and HA is called a strong... 

Table 9-2. Values of K, pK , K, and pK for Selected Conjugate Acid-Base Pairs...

Singh, A.K. and PK. Seth. Degradation of Malathion by Mictootganisms Isolated from Industrial Effluents, Bull Environ. Contam. Toxicol, 43(l) 28-35 (1989). 

There is an inverse relationship between K, and pK, and a large Ka or a small pK is associated with a stronger acid. 

Table 2. Predicted intrinsic and apparent pKa values for the Cys403 residue in Yersinia phosphatase for different models of the structure the data refer to a temperature of 293 K and an ionic strength corresponding to 150 mM of monovalent salt. See the text for the detailed description of the conditions under which each pK estimation was made. The experimentally determined value is 4.67 [39]...

When substances ionise their neutral species produce positive and negative species. The ionisation constants are those constant values (equilibrium constants) for the equilibria between the charged species and the neutral species, or species with a larger number of charges (e.g. between mono and dications), l ese ionisation constants are given as pK values where pK = -log K and K is the dissociation constant for the equilibrium between the species [Albert and Serjeant The Determination of Ionisation Constants, A Laboratory Manual, 3rd Edition, Chapman Hall, New York, London, 1984, ISBN 0412242907]. 

Nitrophenol [554-84-7] M 139,1, m 96 , b 160-165 /12mm, pK 8.36. Crystd from water, CHCI3, CS2, EtOH or pet ether (b 80-l(K)°), and dried under vacuum over P2O5 at room temperature. Can also be distd at low pressure. 

The equivalent expression for polyprotic acids, zwitterions and weak bases are qiven in ref. 339. Froe equation (4.24) it can be seen that the relationship between k and pH is sigmoidal with an inflection point at the pH corresponding to the pK, of the acid. A snail change in the pH near the pK, value for the acid results in a large change in k but at extrene values with respect to the pl ... 

Meena K, Gupta PK, Bawa SR. 1978. Endrin-induced toxicity in normal and irradiated rats. Environ Res 16 373-382. 

Distinguish between PD and PK. For PD, explain the term K, and show how drugs interact with receptors. For PK, explain the mechanisms of ADME. 

---