Isoelectric point, 281 organic compounds

Size, Concentration and Organization of the Molecules. Coacervate drops can range in size from several tenths of a micron to several hundred microns or even larger in diameter. The size of coacervate drops is affected by several factors. At the optimum temperature for the existence of a coacervate, the drops are largest. Coacervate drops are smaller when they consist of compounds whose isoelectric points are widely separated, and larger when the compounds have closer isoelectric points. The diameter of drops also increases with the concentration of the initial solutions from which the coacervates were obtained (11). 

Wang et al. [607] studied the adsorption of dissolved organics from industrial effluents onto a commercial activated carbon. As illustrated in Table 20, they place emphasis on the pK, pK, or isoelectric point of the adsorbate and state that the pH effect upon the effectiveness of carbon adsorption mainly depends upon the nature of the adsorbed substance. Based on their own work and analysis of the literature, they postulate that maximum adsorption of organic acids and bases occurs around their respective pK , or pKh value, even though they acknowledge, at least as the ionic organic compounds become more complex, that electrostatic adsorption forces between the adsorbent and the ionic adsorbate appear to govern. ... 

P-Lactams are sensitive to acids and bases, and this sensitivity varies with the nature of the sidechain. The maximum stability of monobasic compounds such as Pen G is exhibited in the pH range 6-7, whereas for ampicillin (an amphoteric compound), the maximum stability occurs at its isoelectric point of pH 5. The highly susceptible f)-lactam nitrogen is prone to attack by nucleophiles such as methanol. Furthermore, this nucleophilic attack is accelerated by acid catalysis and application of heat. They are also readily isomerized in an acidic environment. f)-lactams are typically extracted with water and/or polar organic solvents from solid matrices. 

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