Organic Nitrogen Compounds - Cultural Connection

\

Organic Nitrogen compounds are a very important part of every day life. One of the most used and influential organic nitrogen compounds is TNT, or trinitrotoluene. TNT does have other uses in chemistry as a reactant to transfer charges on salts. TNT is a yellow solid, and although it is used in chemical reactions, its primary use is as an explosive. 

TNT's yield as an explosive is considered the standard from which all other explosions/bombs are judged. Often, TNT is confused with dynamite as being the same thing. However, the two are not similar at all. Dynamite is made of an absorbent medium coated in nitroglycerin and wrapped in a holding tube. TNT on the other hand is an actual compound, trinitrotoluene. TNT was discovered in 1863 by Joseph Wilbrand. At first TNT was not considered an explosive because of the difficulty in igniting the compound. In fact, in a British explosive control act in the late 19th century TNT wasn't even considered an explosive. One reason that this could be true is because of the stability of TNT. Although a powerful explosive, TNT can be poured easily and doesn't react to shock and movement like previous explosives. The stability, yet strength of TNT is the reason it has been incorporated into the majority of bombs over the years.

TNT was first incorporated into bombs by the Germans in 1902. Previously lyddite ( shown below ) had been used in bombs.

However, the lyddite wasn't as stable and when it hit the shell of ships it would explode immediately. The TNT though would make it through the hull and explode inside, causing much greater damage. The British realized the extra ability of the TNT and replaced their shells with it in 1907. The United States today uses TNT widely in many of its bombs. Much of the TNT produced in the United States comes from Virginia

Production of TNT is a very dangerous business because of the toxicity of the compound. TNT causes skin irritation and even a yellow coloring of the skin. The workers that formed TNT in world war one didn't have proper protection, and as a result there skin turned yellow. These workers gained the nickname of canaries because of the yellow coloring of their skin.

Application for Organic Nitrogen compounds - Role of Protein in Hair

Protein is made up of polypeptides which is a polymer composed of amino acids. In other words, amino acids are building blocks of proteins. There are currently 22 natural occurring amino acids.

There are generally two classes of proteins, namely the fibrous proteins and globular proteins. Fibrous proteins are structural proteins which are filament-like and elongated in shape and confer mechanical properties on the proteins due to the secondary structure that the amino acids sequence favour. Globular proteins are folded into compact structures and it is typically used for synthesis, transport and catabolism.

 Disulfide bond formed between two cysteine molecules

The major protein found in hair and fingernails is alpha-keratin which is a fibrous protein. Its secondary structure is predominantly alpha-helices. The protein strands within hair and other alpha-keratins are crosslinked to some extent by covalent bonds between cysteine residues to form disulfide bonds. The chemical composition of the cysteine residues in alpha-keratin affects its macromolecular structure and function. For example, the characteristics of hair (straight, curly etc) is based on the disulfide bonds present in the hair protein. The more such disulfide bonds there are between the strands, the more rigid the protein becomes as a whole.

Coil Structure of the alpha-keratin in hair

Credits: http://www.pearsonhighered.com/mathews/ch06/c06fp.htm

The disulfide bonds are very strong covalent bonds which cannot be broken by simply heating. In order to curl straight hair, the disulphide bonds have to be broken chemically by reduction, form the desired shape by curling and form new disulfide bonds by oxidation to maintain the new shape. 

Application for Organic Nitrogen compounds - Nylon

Nylon is a synthetic polymer produced in 1935 by Wallace Carothers. It is very commonly used and has several variations such as nylon-6,6, nylon-6,9, nylon-11.

Uses:
Toothbrush Bristles
Stockings
Fabric
Instrument strings

Nylon is made of repeating units linked together by amide linkages (bonds)


Manufacture:

Molecules with an acid (-COOH) group are reacted with molecules containing amine (-NH₂) groups. The resulting nylon is named on the basis of the number of carbon atoms separating the two acid groups and the two amines. This process is known as condensation and it produces a monomer with an acid group on one end and an amine group on the other end know as the monomer as shown below.



The monomer which then continues to form more linkages to form longer polymer chains.

Nylons of various types are manufactured using slightly different conditions to vary there chain length and arrangement to give different physical properties.

Application for Organic Nitrogen compounds - Nitrogenase

 

N2 + 8 H+ + 8 e- + 16 ATP + 16 H2O à 2 NH3 + 16 ADP + 16 Pi + H2 + 16 H+

 

Structure of Nitrogenase:

[Fe]-protein (60 kDa)  +  a2b2  [MoFe] protein (each subunit 60 kDa)

 

• The folding of the enzyme nitrogenase is due to its primary, secondary, tertiary and quartenary structure.
• a-helix and b-pleated sheets can be observed from the picture shown above.
• Other forces of attraction are also involved in stabilising the tertiary structure, eg. electrostatic forces between charged groups and hydrogen bonding between polar groups.
• Each of the polypeptide subunit adopts a tertiary structure to give the characteristics of the protein.

 

Nitrogenases have two component proteins:

• Fe-protein: functions as the e- donor; is a dimeric protein with a M.W. ~ 60 kDa. Has a [4Fe-4S] cluster which 1st receives e-, stores them and finally donates them to the site where N2 is reduced.
• Fe-Mo protein (in cases it is a Fe-only or Fe-V protein): A Fe-Mo cofactor of this protein is the actual site where N2 binds and is reduced.
• A P cluster within this protein is believed to be involved in e- transfer from the reduced [4Fe-4S] cluster of the Fe protein to the Fe-Mo cofactor.

Nitrogenase is the enzyme involved in some organisms to fix atmospheric nitrogen gas. As the N≡N triple bond is very high in energy, dinitrogen is quite inert. With the Fe-Mo cofactor, formation of multiple Fe-N interactions weakens the N≡N triple bond and lowers the activation energy barrier for the reduction. This can generate ammonia gas which is required by fertillisers.

 

Related process that produces ammonia gas from the reaction of nitrogen gas and hydrogen gas is the Haber process.