BIOCHEMISTRY - Textbook - Ostapchenko L. I. - 2012

Chapter 1. STRUCTURE AND REACTIVITY OF BIOORGANIC COMPOUNDS

1.3. Selected Classes of Bioorganic Compounds and Their Biological Significance

1.3.4. Bioorganic Nitrogen Compounds

Nitrogen-containing hydrocarbon derivatives include nitro compounds and amines, in which hydrogen atoms are replaced by NO₂ and NH₂ groups, respectively, as well as amides, which are products of replacing the OH group in the carboxyl of carboxylic acids with NH₂. Nitro compounds (R-NO₂) are classified into aliphatic (saturated - nitroalkanes, unsaturated - nitroalkenes) and aromatic (nitroarenes). In nitro compounds, the nitrogen atom and both oxygen atoms are in an sp²-hybridized state, and the electronic Structure OF THE nitro group represents a Resonance structure with limiting forms:

Class="center">

The reduction of nitro compounds yields primary amines:. The reduction products of nitroalkanes are alkanamines:The reduction of Aromatic Compounds (Zinin reaction) yields aniline and its derivatives. The intermediate reaction products are nitroso compounds (containing the N=O nitroso group) and hydroxylamine:

Amines are classified into primary (RNH₂), secondary (R₂NH), and tertiary (R₃N). According to the Chemical Nature of their radicals (R), amines are subdivided into aliphatic (R is non-cyclic), aromatic (R is a benzene derivative), and aliphatic-aromatic. Diamines—compounds containing two amino groups—constitute a separate group. In turn, aliphatic, aromatic, aliphatic-aromatic, and diamines can be primary, secondary, or tertiary. Diamines are widespread in living organisms; for instance, putrescine (1,4-butanediamine) - H₂-(CH₂)₄-NH₂ and cadaverine (from cadaver - corpse; 1,5-pentanediamine) - H₂-(CH₂)₅-NH₂, which accumulate during tissue putrefaction, as well as spermine - H₂-(CH₂)₃-NH-(CH₂)₄-NH-(CH₂)₃-NH₂, which is involved in The regulation of METABOLISM/36.html">DNA Replication. The Basic Properties of amines include their interaction with acids to form ammonium salts, alkylation and acylation reactions yielding substituted carboxylic acid amides, and substitution reactions in the aromatic ring of amines, notably the synthesis of sulfanilic acid from aniline. This acid is a structural component of sulfonamides—antimicrobial agents that include the well-known streptocide (sulfanilamide). The Mechanism of the bacteriostatic effects of sulfonamide drugs relies on the competitive inhibition of bacterial Enzymes that utilize p-aminobenzoic acid as a substrate to produce Folic acid (vitamin B_c), which is essential for bacterial growth. p-Aminobenzoic acid also serves as a Starting Material for the synthesis of local anesthetics, such as anesthesin, novocaine, lidocaine, etc.

The anesthetic effect of these substances is due to the blockade of sodium channels in the postsynaptic membrane, which halts the propagation of nerve impulses.

Acid amides (R-CO-NH₂) can be viewed as products of replacing the OH group in the carboxyl of carboxylic acids with an NH₂ group, or as the result of replacing a hydrogen atom in an ammonia molecule with An acyl group. Amidation reactions are crucial in biochemical processes, a prime example being The formation of The amino acid glutamine from glutamic acid:

Amino Acids are covalently linked via a substituted amide bond (see Table 1.1). The formation of a peptide bond via the nucleophilic substitution of hydroxyl groups in natural amino acid molecules by an amino group is discussed in Chapter 5.