Azo Functional Group

The Azo compounds are in general used in the leather and textile enterprise in form to dyes and pigments and more in the prescription drugs industries to develop drugs. Azo compounds are compounds containing the function crew of R-N=N-. P-Griess is the first scientist to discover the Azo compounds through the manner of diazo-coupling in 1858. The Azo compounds can be from diimide. HN=NH which are derivatives of diazene, consequently, the hydrogen present can be substituted by the fragrant compound like benzene to form diphenyl diazene. Azo compounds can show that the isomerism (trans-cis).The most steady compounds is the cis isomer

The preparation of the Azo compounds

Azo coupling through electrophilic substitution: the most electron-donating attacks aryl or alkyl group.

ArN+2 + Ar′H → ArN=NAr′ + H+ Ar -aliphatic or aromantic compounds

Oxidation of the hydrazine gives Azo compounds. Diazonium salts unstable therefore the reaction of coupling is conducted at a room temperature (Lumm et al. 470).

ArNO2 + Ar′NH2 → ArN (O) =NAr′ + H2O

ArN (O) =NAr′ + C6H12O6 → ArN=NAr′ + C6H10O6 + H2O

Azo groups generate electron deficiency due to the electron withdrawing character. Component of the Azo compound tends to react to the aerobic condition. Because it’s less susceptible to the oxidative metabolism but the physicochemical parameter of the Azo compounds such as aniline, benzidine, and naphthalene varies.

The acute toxicity of the animals is through oral, skin or irritation. Exposure to the Azo compounds causes methemoglobinemia. The oxygen binding can occur when the amine oxidizes the iron in hemoglobin from Fe2+ to Fe3+. This will cause diseases like cyanosis of nose and lips, dizziness, and weakness (Stumm et al. 154). The Azo linkage undergoes enzymatic breakdown in mammals where it is separate into two molecules. Anaerobic lower gastrointestinal of the mammals is well suited for the Azo-reduction. The path for the detoxification Azo compounds is through glucuronide conjugation and ring hydroxylation.

Bacteria degrade Azo compounds at an anaerobic process. Where there is biodegrading of the Azo dyes, there is two-step aerobic or anaerobic process in high uptakes and Azo reductase (Stumm et al. 154). Color removing fungi in the dye depends on the presence of the nitrogen.

The fungi, bacteria, Protista, archaebacteria and eubacteria bio grade the Azo compounds in the anaerobic environment. There are acetylation, carboxylation, and hydroxylation of the aromatic ring. Bacteria degrade through the cell wall membrane; fungi degrade through extracellular.

In plant, there is presence of the chromophores molecules (-N=N-) which contributes to the chemical and physical properties. Pigment green and malachite green contains the structure containing the Azo compounds. Chromophore contains pie electrons which undergoes electronic transition in presence of ultra-violent light, which is responsible for the appearance of the color in the dyes. Therefore, the extraction of the dye component in the plants contains the Azo groups. Hence, the conjugated molecules absorb lights at different wavelength.

Hormones such as epinephrine are amino acid derivatives derived from amino acids which is water soluble molecules, and building block of protein .They act by binding to the outside of the cell, the second molecules activates the enzymes which influencing the gene expression

Proteins also contain Azo group as an amine group. Amino acid dissolves in the water; there is a transfer of the photon to the amine from the carboxylic ensure particular PH exist which is called zwitter ion. PH of occurrence is known as the isoelectric point. Therefore, the presence of the Azo compounds in the protein makes it resist changes in PH.

Without the Azo containing molecules, an organism could hardly live. The components of the proteins, nucleotides, enzymes and lipids are major molecules in the body of the living organism (Brett et al. 31). Nitrogen base is essential in the production of new proteins for the cells. Nucleotides are the major component of the formation of the ribonucleic acids and deoxyribonucleic acid.

NH2CHRCOOH (aq) + H+ (aq)NH3+CHRCOOH (aq). In acid

NH2CHRCOOH (aq) + OH- (aq)NH2CHRCOO- (aq) + H2O In base (Sandler et al. 81)

Coenzymes are the protein that increases the digestion during the chemical reaction. But the protein is less important for the fungi, bacteria and plants.

Nucleotides are building a block of the nucleic acid (Kaneko et al. 19). The Azo ground in the nucleotides forms a nitrogen base which combines with sugar like ribose to form nucleoside.

Compounds containing aliphatic Azo functional group participate as a catalyst in the vinyl radical polymerization due to thermolytic fission into free radicals and nitrogen.

Azo compounds due to the vivid color acts as dyes .an example of the dye are methyl orange and methyl red. Methyl red dye turns red in an acidic media solution. Azo compounds are acid-base indicators. PH below 4.4 methyl red is red but turns yellow at the PH above 6.2. Change in color shows that the Azo functional group is affected by PH. Delocalization of n (pi) electrons contributes to the chemical reactivity of the Azo compounds due to the formation of their acid and basic salts (Sandler et al. 81).

Azo compound is a good oxidizing agent, thus undergoes reduction process. Compound undergoes reduction to primary amine or hydrazine (Harvey and Ronald 50). Component containing the Azo functional group undergoes the nucleophilic addition or oxidation –reduction reaction.

For example the azides R-N3 in the presence of hydrogen ion concentration (H+) it is reduced to the primary (10) amine. Catalyst presence is palladium or lithium aluminum hydride (LiAlH4)

One of utmost importance of the Azo compound is the manufacture of the medicine such as phenazopyridine (Pyridium).The chemical has a formula of C11H11N5 with a relative molecular mass of 213.239g/mol. It relieves the pain during urination due to the local analgesic effects in the urinary tract. Additionally, the Azo compound acts as a coupling agent in the biological essay. Cross-linking of the Azo polymers can produce Azo linkages such as olsalazine, ipsalazine, sulfasalazine, and balsalazine.

Azo compounds, when combined with another chemical, are very explosive. For instance, the reaction of the azide (-N3) forms insoluble salt when reacted with a heavy metal such as mercury or lead. As a result of Conjugation of the N=N bond of the Azo compound, the bond split at N=N bond due to the radical formation.

C6H5 - NH2 + HNO2 + H+® C6H5 - N+ºN: + 2H2O

The diazonium cations are more stable than aliphatic parts. Benzene diazonium salts are very explosive in the solid state but are stays in the solution (Sandler et al. 81).

The Azo compounds assist in the degradation in photolysis and hydrolysis in abiotic system. Degradation mechanism takes place at PH range (4-9). Reductive cleavage of the Azo compound in the Azo bonds is the route for the Azo dye degradation. Photodecomposition of the Azo in pure water is high due to the oxidation of the oxygen or oxy-radicals while reduced oxygen water the decomposition is very slow

Works Cited

Brett, Christopher T., and Keith W. Waldron. Physiology and biochemistry of plant cell walls. Vol. 2. Springer Science & Business Media, 1996.

Harvey, Ronald G. Polycyclic aromatic hydrocarbons: chemistry and carcinogenicity. CUP Archive, 1991.

Kaneko, Jiro Jerry, John W. Harvey, and Michael L. Bruss, eds. Clinical biochemistry of domestic animals. Academic press, 2008

Lunn, George, Louise C. Hellwig, and C. Hellwig. Handbook of derivatization reactions for HPLC. Vol. 467. New York: Wiley, 1998.

Sandler, Stanley R., and Wolf Karo. Organic functional group preparations. Vol. 2. Elsevier, 2013.

Stumm, Werner, and James J. Morgan. Aquatic chemistry: chemical equilibria and rates in natural waters. Vol. 126. John Wiley & Sons, 2012.