An Introduction to Nitro Compounds
Nitrogen is necessary for all living beings, and it forms a vital constituent of cells in the form of proteins, DNA, RNA and amino acids. Nitrogen forms complex compounds, such as nitrous oxides and ammonia, which gets used in various industrial and clinical purposes. Mostly, nitro compounds find their applications to produce fertilisers for promoting crop growth.
If you are studying about these complexes, you must not skip learning about nitro compounds properties. Learn related conceptions with great detail to score well in your exams.
What is Nitrogen Compound?
Nitrogen forms many different types of compounds, such as ammonia, nitrous oxides, cyanide, etc. Azides can be inorganic or organic compounds of nitrogen, which comprises of three nitrogen atoms within a group (N3). The compounds comprising of nitrogen arise from a chemical reaction known as nitration, which happens when nitric acts react with an organic compound.
In nature, nitrogen complexes form through various processes, such as nitrification and de-nitrification.
Through nitrification, nitrogen-fixing bacterias present within the soil help in the conversion of ammonia into nitrite. This, in turn, gets converted into nitrates. These complex compounds are taken up by the plants and used in forming animal and plant proteins.
De-nitrification is a process where de-nitrifying bacteria helps in completing the nitrogen cycle through the conversion of nitrate (NO3) back into nitrogen gas (N2). They release nitrogen gas back into the atmosphere from nitrates by removing oxygen.
Read from below about some common types of nitrogen compounds. These include:
Properties of Nitrogen Compounds
Nitrogen compounds occur when nitrous action acts on any organic compound through nitration. Some of the nitro compounds properties are as follows:
Ammonia:
Ammonia, one of the nitrogen consisting compounds, is a colourless gas having a strong, sharp smell.
It has a boiling point of 33.35 degree Celsius and a freezing point of 77.7 degree Celsius along with high vaporisation.
A molecule of ammonia comprises of three atoms of hydrogen and a single nitrogen atom.
Ammonia is a polar molecule attached with strong intermolecular forces due to hydrogen bonding.
Nitrous Oxide:
At normal temperatures, it is heavier than gas having a specific gravity more than 1.53 times.
At room temperature, it exists in a gaseous state, whereas it becomes a liquid after being compressed in a cylinder.
The boiling point of nitrous oxide is -89 degree Celsius, and its density equals to 1.22g/cm3.
At normal temperature, it occurs as a gas without any colour with a sweet smell and taste.
It is also known popularly as laughing gas because when anyone inhales it, produces continuous laughter along with insensibility to pain.
Di-nitrogen oxide is highly insoluble in water and blood.
Moreover, it is not flammable, although it allows the combustion of other materials when it comes in close contact with them.
Nitrate:
Mostly, all nitrate salts get dissolved in water quickly.
Nitrates are nitrogen-based compounds formed due to reduction of a proton from nitric acid (HNO3).
The molecular weight of this nitrogen comprising compounds is 62.005 g/mol.
The number of hydrogen bond donors and acceptors is 0 and 3, respectively.
The di-nitrogen oxide’s exact mass accounts to 61.987818 g/mol same as its mono-isotopic mass.
Nitrites:
Nitrites are nitrogen-based compounds formed because of the deduction of a proton from nitrous acid.
At normal temperatures, it appears as a solution without any colour or crystalline solids.
It is usually denser than water.
When this nitrate compound comes in close contact with eyes, skin or nose, it may result in irritation. It is also harmful if consumed.
The molecular weight of this nitrogen compound accounts to 46.006 g/mol.
Its number of hydrogen bond donor and acceptor equal to 0 and 3 similar to nitrates, respectively.
The exact mass of this nitrogen comprising compound amounts to 45.992903 g/mol similar to its mono-isotopic mass.
The number of nitrites heavy atom is 3, whereas the number of isotope atom amounts to 0.
Urea:
Urea, an organic nitrogen-based compound, forming within the liver, gets dissolved quickly. Usually, minimal amounts of urea get exhibited through human sweat.
The molecular weight of urea (nitrogenous compound) accounts to 60.056 g/mol.
The exact mass of this nitrogen comprising compound equals to 60.032363 g/mol identical to the mono-isotopic mass of urea.
The number of heavy atom amounts to 4, whereas the number of isotope atom amounts to 0.
The complexity of this nitrogen compound amounts to 29.
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Applications of Nitrogen Compounds
Nitrogen-based compounds find various uses. Read these popular applications to know more:
Nitric acid (HNO3) is a compound comprising of nitrogen, used in the manufacture of fertilisers, plastics and dyes.
Pyrazines, a cyclic compound comprising of nitrogen acts as a flavour enhancer of many baked and natural foods. They also add to the aroma in grapes and wines.
Ammonia gets mostly used in the manufacture of fertilisers, and various industrial activities.
Di-nitrogen oxide also gets used as a fuel in most of the food aerosols. In racing automobiles, it gets used in engines.
Nitrous oxide (N2O) also popularly known as laughing gas, gets used for anaesthesia in hospitals and dental applications due to its clinical properties.
Nitric acid also finds its applications in the production of explosives like nitroglycerin. Nitroglycerin is a liquid used in the manufacture of dynamite. Also, it has applications in the military for construction purposes.
Urea, one of the well-known nitro compounds, gets used as a raw material in industries apart from use in fertilisers.
Plants:
Apart from the clinical and industrial applications, nitro compounds also provide benefits to plants. These include:
As soon as nitrogen transforms into complex compounds, plants take these up from the soil to transfer them to other portions. These complexes also find applications in forming macromolecules (proteins and nucleic acids).
One of the primary applications of amines (one of the organic nitrogen compounds) is that it gets used as ammonium salts for promoting the growth of crops. Crops like sugarcane and rice require these salts for steady growth.
It also gets used in the manufacture of chlorophyll in plants which is an essential component for photosynthesis.
Interesting Facts about Chemical Nitrogen and its Compounds
Nitrous oxide is a greenhouse gas, and it is also a potential air pollutant. In terms of weight, it has an impact of 300 times more than carbon dioxide.
Nitrogen is a chemical element having a symbol (N) with a number of isotopes 4.
Nitrous oxide also finds uses in motor racing as it can enhance the power of the engine along with its speed.
Nitrogen has the atomic number 7, and it is a colourless non-metal gas without any odour.
Nitrogen is a tasteless gas present in all living organisms, such as human beings, plants and animals.
Nitrogen gas often gets used in place of carbon dioxide for storage of beer, as it can produce smaller bubble suitable for maintenance of liquor.
Test Your Knowledge
What will be the amine ‘A’ when it acts with nitrous acid exhibiting an oily, yellowish substance?
Aniline
Tri-methylamine
Methylphenylamine
None of these
What will be the formation when aniline reacts with chloroform (under alkaline circumstances)?
Cyanide
Phenyl isonitrile
Isocyanate
None of them
Which of these will not follow azo coupling reaction when it comes with benzene diazonium?
Aniline
Cyanide
Nitrobenzene
None of the above
Organic chemistry is a vast subject. Students often get confused because they do not have in-depth knowledge of the concepts. If you have any doubts related to nitro compounds class 12, just go through the above pointers carefully. You can also visit our website for live classes to understand the problematic concepts of Chemistry clearly. Now you can even download our Vedantu app for better access to these detailed study materials and online sessions.
FAQs on Nitro Compounds
1. What are nitro compounds in organic chemistry?
Nitro compounds are organic compounds that contain one or more nitro functional groups (-NO₂) attached to a carbon atom. They are classified into two main types based on the hydrocarbon framework:
- Aliphatic nitro compounds: Where the -NO₂ group is attached to an alkyl group (e.g., nitromethane, CH₃NO₂).
- Aromatic nitro compounds: Where the -NO₂ group is attached directly to an aromatic ring (e.g., nitrobenzene, C₆H₅NO₂).
2. What is the structure of the nitro group?
The nitro group (-NO₂) has a unique structure that is best described as a resonance hybrid. The central nitrogen atom is bonded to two oxygen atoms. It has a formal positive charge, while one oxygen carries a formal negative charge. The structure involves resonance between two equivalent forms, meaning the N-O bonds are of equal length, intermediate between a single and a double bond.
3. How are aromatic nitro compounds like nitrobenzene prepared?
Aromatic nitro compounds are typically prepared through a process called electrophilic aromatic substitution. For example, nitrobenzene is synthesized by treating benzene with a nitrating mixture, which is a combination of concentrated nitric acid (HNO₃) and concentrated sulfuric acid (H₂SO₄) at a controlled temperature (around 50-60°C). The sulfuric acid acts as a catalyst to generate the highly reactive nitronium ion (NO₂⁺), which is the electrophile that attacks the benzene ring.
4. What are the major applications of nitro compounds?
Nitro compounds are highly valuable in various industries for several applications, including:
- Synthesis of Amines: The reduction of aromatic nitro compounds is the primary industrial method for producing aromatic amines. For instance, aniline is manufactured by reducing nitrobenzene.
- Explosives: Many polynitro compounds are powerful explosives due to their ability to undergo rapid decomposition. Examples include TNT (Trinitrotoluene), picric acid, and RDX.
- Solvents: Some nitroalkanes are used as solvents for polymers, resins, and other organic substances.
- Intermediates: They serve as crucial intermediates in the synthesis of dyes, pharmaceuticals, perfumes, and rubber chemicals.
5. What is the difference between a nitro group (-NO₂) and a nitrite group (-ONO)?
Although they have the same chemical formula, the nitro and nitrite groups are isomers with different structures and properties. The key difference is the point of attachment:
- In a nitro group (-NO₂), the carbon atom is directly bonded to the nitrogen atom.
- In a nitrite group (-ONO), the carbon atom is bonded to an oxygen atom, which is then bonded to the nitrogen atom.
6. Why is the nitro group considered a deactivating group in aromatic compounds?
The nitro group is a powerful electron-withdrawing group. It deactivates the aromatic ring towards further electrophilic substitution through two effects:
- Inductive Effect (-I): The high electronegativity of nitrogen and oxygen pulls electron density away from the ring through the sigma bond.
- Resonance Effect (-R): The nitro group can pull electron density from the ring via resonance, particularly from the ortho and para positions.
7. How does the nitro group influence the direction of substitution on a benzene ring?
Because the nitro group is strongly electron-withdrawing, it deactivates the ortho and para positions more significantly than the meta position. The resonance structures show a positive charge developing at the ortho and para carbons, making these sites highly unfavoured for attack by an incoming positive electrophile. Consequently, the meta position becomes the most relatively electron-rich site, directing the new substituent to bond there. Therefore, the nitro group is known as a meta-director.
8. How does the presence of a nitro group affect the acidity of phenol?
The presence of a nitro group significantly increases the acidity of phenol. As a strong electron-withdrawing group, it helps to stabilize the phenoxide ion formed after the proton (H⁺) is lost. This stabilization occurs by delocalizing the negative charge over the aromatic ring and onto the nitro group itself. The more stable the conjugate base (phenoxide ion), the stronger the acid. This effect is most pronounced when the nitro group is at the ortho or para position.
9. Why are many polynitro aromatic compounds like TNT (Trinitrotoluene) explosive?
Polynitro compounds are explosive because they have both the fuel (the carbon and hydrogen framework) and the oxidizer (the oxygen-rich nitro groups) within the same molecule. When initiated by heat or shock, they undergo a very rapid internal redox reaction. This decomposition releases a massive amount of energy and produces a large volume of stable, hot gases (like N₂, CO₂, H₂O), creating a powerful explosion.
