TY - CHAP M1 - Book, Section TI - Acid-Base Chemistry of Organic Molecules A1 - Miller, Susan A2 - Renslo, Adam PY - 2016 T2 - The Organic Chemistry of Medicinal Agents AB - While carbon (C) and hydrogen (H) form the foundation of organic molecules, the rich diversity and specificity of interactions between biological and drug molecules arises from the presence of heteroatoms (N, O, S, P, halides) when they combine with C and H to form various functional groups. One property of many heteroatom containing molecules is a certain acidity or basicity at physiological conditions that can contribute to the reactivity and physiochemical properties of the molecule. Although drug molecules are often designed to have little or no chemical reactivity as administered, once absorbed they are metabolized (i.e., undergo chemical conversions catalyzed by the enzymes of drug metabolism) to give products with new functional groups having enhanced reactivity, potentially leading to adverse side effects. In addition to influencing reactivity, acid/base properties and the charge state of a drug molecule contribute significantly to its relative solubility in water (as found in the interior of cells and in bodily fluids) versus nonpolar media (as found in the lipid membranes of cells). This differential solubility impacts the absorption of the drug and hence the amount that needs to be administered to achieve the desired effect. In this chapter, we review the principal models of acid and base behavior and discuss the relationship of structure and bonding to the acidity of different types of “X–H” bonds (C–H, N–H, O–H, S–H) and the basicity of the lone pairs of electrons on the corresponding “X” atoms (:N, :O, :S). SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/10/16 UR - accesspharmacy.mhmedical.com/content.aspx?aid=1124842587 ER -