Organic compounds, hydrogen-bond rules

Table I. Hydrogen-bond Rules for Organic Compounds...

The enzymes are protein molecules having globular structure, as a rule. The molecular masses of the different enzymes have values between ten thousands and hundred thousands. The enzyme s active site, which, as a rule, consists of a nonproteinic organic compound containing metal ions of variable valency (iron, copper, molybdenum, etc.) is linked to the protein globule by covalent or hydrogen bonds. The catalytic action of the enzymes is due to electron transfer from these ions to the substrate. The protein part of the enzyme secures a suitable disposition of the substrate relative to the active site and is responsible for the high selectivity of catalytic action. 

One of the great rules of thumb in chemistry is like dissolves like. That means that polar solutes are more soluble in polar solvents, while nonpolar solutes are more soluble in nonpolar solvents. We have discussed molecular polarity in a previous chapter, but you can consider most organic compounds to be nonpolar. The most polar species are, obviously, ionic compounds, followed by species that can form hydrogen bonds, such as water and ethanol (CH3CH2OH). Therefore, you would expect ionic compounds to be soluble in water, but not very soluble in an organic solvent such as ether or hexane. On the other hand, you would expect an organic compound, like the vast majority of the pure form of injectable medications, to be relatively insoluble in a water-based medium such as blood. 

Organic compounds generally conform to the following generalized rules in regard to hydrogen bonding ... 

Most of the common elements in organic compounds—C, N, O, and the halogens— follow the octet rule. Hydrogen is a notable exception, because it accommodates only two electrons in bonding. Additional exceptions include boron and beryllium (second-row elements in groups 3A and 2A, respectively), and elements in the third row (particularly phosphorus and sulfur). 

Organic compounds typically have complex struetural formulas that consist of chains, branches, and/or rings of earbon atoms bonded to hydrogen atoms and, often, to atoms of oxygen, nitrogen, and a few other elements. At this point, we ll see how the simplest organic compounds are named. Mueh more on the rules of organie nomenelature appears in Chapter 15. 

Hydrogen bonding vctsus proton transfer and the nature of the hydrogen bond, both in the liquid and in the gas phase, are subjects of extensive investigations and useful empirical rules to draw hydrogen bond patterns are well codified for organic compounds . 

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