Dinitrogen Pentoxide – Preparation and Usage

Dinitrogen Pentoxide

What is N₂O₅? N₂O₅ compound name is Dinitrogen Pentoxide or Nitrogen pentoxide or Nitro Nitrate. The N₂O₅ name symbolizes two nitrogen atoms and five oxygen atoms in a molecule. Dinitrogen pentoxide is the nitric acid’s anhydride form. It occurs as white crystals when ozone oxidizes nitrogen dioxide.

It is also obtained by dehydrating HNO₃ with diphosphorus pentoxide. The compound is unstable and decomposes into oxygen and nitrogen dioxide at room temperature. It is a mildly explosive chemical with little commercial value.

Preparation of Dinitrogen Pentoxide

Method 1:

It can be prepared from concentrated nitric acid (HNO₃) and phosphoric anhydride (P₄O₁₀). This process is preferred for laboratory synthesis.

12 moles of concentrated nitric acid react with phosphoric anhydride to give 6 moles of dinitrogen pentoxide and 4 moles of phosphoric acid.

The chemical equation for the reaction is as follows:

12 HNO₃ + P₄O₁₀ → 6 N₂O₅ + 4 H₃PO₄

Method 2:

Another laboratory synthesis involves lithium nitrate LiNO₃ and bromine pentafluoride BrF₅.

3 moles of lithium nitrate react with 1 mole of bromine pentafluoride. The ratio remains 3:1, while the quantity might vary. The reaction gives nitryl fluoride that further reacts with lithium nitrate to give lithium fluoride and dinitrogen pentoxide.

BrF₅ + 3 LiNO₃ → 3 LiF + BrONO₂ + O₂ + 2 FNO₂

FNO₂ + LiNO₃ → LiF + N₂O₅

Method 3:

It can also be prepared from nitric acid (HNO₃) and phosphorus pentoxide (P₂O₅).

2 moles of nitric acid react with phosphorus pentoxide to give dinitrogen pentoxide and 2 moles of meta-phosphoric acid.

The chemical equation for the fraction is as follows:

2 HNO₃ + P₂O₅ → N₂O₅ + 2 HPO₃

Method 4:

It is also created in the gas phase when nitrogen dioxide (NO₂) or dinitrogen tetroxide (N₂O₄) reacts with ozone.

2 moles of nitrogen dioxide gas react with one mole of ozone to give dinitrogen pentoxide and oxygen.

The reaction can be stated as follows:

2 NO₂ + O₃ → N₂O₅ + O₂

The product catalyzes the decomposition of ozone. Thus, it is one of those gasses that are responsible for ozone depletion.

Did you Know: Dinitrogen pentoxide was first reported in 1840 by Deville. He prepared it using silver nitrate (AgNO3) and chlorine.

Structure of Dinitrogen Pentoxide

The crystal structure of N₂O₅ is hexagonal. Its molecular shape is planar. It is a binary compound with two elements– nitrogen and oxygen. It is solid but sublimates to a colorless gas as the temperature rises above room temperature.

Solid dinitrogen pentoxide is a salt. It has separate cations and anions. While the cation nitronium ion has a linear structure, the anion is planar. Thus, the solid dinitrogen pentoxide can also be called nitronium nitrate. The nitrogen centers have five as the oxidation state.

Structure of Dinitrogen Pentoxide

• The total number of atoms is 7.
• Total valence electrons are 10 + 30 = 40.
• Electrons required for octet are 56.
• Electrons lacking will be required for octet – total valence electron (56 – 40 ) = 16.
• The total number of bonds formed will be 16/2 = 8 bonds.

Physical Properties of Dinitrogen Pentoxide

The following table states some important properties of N₂O₅

• Molecular Wt/ Molar Mass: 108.01 g/mol
• Density: 1.64 g/cm³
• Melting Point: 41 °C
• Boiling Point: 47 °C
• Odor: No odor
• Complexity: 71.2
• Appearance: White solid
• Hydrogen Bond Acceptor: 5
• Covalently-Bonded Unit: 1
• Solubility: Soluble in ether and alcohol
• It is highly acidic.

Calculation of Molecular Weight of Dinitrogen Pentoxide

The formula for the compound is N₂O_5.

The molecular weight of nitrogen is 14.0067.

The molecular weight of oxygen is 15.999.

So, its molar mass can be calculated as follows:

= (2 × 14.0067) + (5 × 15.999)

= 108.01 grams/ mol

Thus, the molar mass or molecular weight of Dinitrogen Pentoxide is 108.01 g/mol.

Chemical Properties of Dinitrogen Pentoxide

Dinitrogen pentoxide is a strong oxidizing agent. It reacts with various substances. Some of the key reactions are as follows:

Reaction with Water

It reacts with water in a ratio of 1:1 to form nitric acid. Thus, the reaction proves that dinitrogen pentoxide is an anhydride of water. The chemical reaction can be written as follows:

N₂O₅ + H₂O → 2 HNO₃

Reaction with Base

It reacts with a base such as sodium hydroxide to give sodium nitrate and water. The balanced chemical equation is as follows:

N₂O₅ + 2 NaOH → 2NaNO₃ + H₂O

Reaction with Acid

Dinitrogen pentoxide reacts with hydrochloric acid (HCl) to give nitric acid and nitryl chloride. The chemical equation is as follows:

N₂O₅ + HCl → HNO₃ + NO₂ Cl

Decomposition

Dinitrogen pentoxide readily decomposes as the temperature rises above room temperature.

Decomposition at Room Temperature

It gives nitrogen dioxide and oxygen. At 0 °C, the decomposition is negligible if placed in inert containers.

2 N₂O₅  → 4 NO₂ + O₂

Decomposition at High Temperatures

At high temperatures between 600 K and 1,100 K or 327–827°C, dinitrogen pentoxide decomposes in two successive steps:

Step 1: N₂O₅ → NO₂ + NO₃

Step 2: 2 NO₃ → 2 NO₂ + O₂

Decomposition in CCl₄ at 30 °C

Besides decomposition at high temperatures, dinitrogen pentoxide decomposes in carbon tetrachloride (CCl₄) at 30 °C or 303 K.

The products formed are nitrogen dioxide and oxygen. While dinitrogen pentoxide and nitrogen dioxide stay soluble in carbon tetrachloride, oxygen being insoluble escapes as a gas. The equation for the reaction is as follows:

2 N₂O₅ → 4 NO₂ + O2(g)

Reaction with Ammonia

Dinitrogen pentoxide gives several products in reaction with amm

onia (NH₃),  including nitrous oxide (N₂O), nitramide (NH₂NO₂), ammonium nitrate (NH₄NO₃) and ammonium dinitramide (NH₄N(NO₂)₂, depending on reaction conditions.

Think about it: Though nitrogen forms pentoxide, it does not form pentachloride. Why? Nitrogen cannot form nitrogen pentachloride because it does not have a vacant d orbital, and it cannot expand its octet. Besides, in dinitrogen pentoxide, there are two nitrogen molecules, so they need not have a d orbital.

Uses of Dinitrogen Pentoxide

Some of the key uses of dinitrogen pentoxide are as follows:

• It is used as a strong oxidizing agent in high-fuel rockets.
• In non-water-based solvents, easy nitration of molecules that are very sensitive to water can happen.
• As a nitrating agent, it helps in modern organic chemistry. A mixture of N₂O₅ and HNO₃ is suitable for nitrating.
• It is used in the preparation of explosives.
• It was earlier used as a reagent for nitrations, but now it is largely superseded by NO₂BF₄.
• As a solution in chloroform, it is used as a reagent to add the −NO₂ functionality in organic compounds. The nitration reaction is as follows:

N₂O₅ + Ar−H → HNO₃ + Ar−NO₂

Biological Effects of Dinitrogen Pentoxide

In addition to physical and chemical properties, it is important to understand the biological effects of dinitrogen pentoxide. Some of the major impacts are as follows:

• Like any other oxide of nitrogen, the inhalation of dinitrogen pentoxide causes toxic effects that mainly target the lungs.
• Less exposure can cause mild irritation in the upper respiratory tract. The symptoms can range from cough, sore throat, headache, conjunctivitis, and vertigo to the tightness of the chest.
• Prolonged exposure can cause pulmonary oedema and lung inflammation.
• Gaseous dinitrogen pentoxide can cause eye irritation or conjunctivitis.
• When the fumes of dinitrogen pentoxide mix with sweat, it can cause skin irritation or skin burns due to nitric acid formation.
• It damages the ozone layer leading to more exposure to UV rays and their harmful effects.

Points to Remember The hybridization of N2O5 is sp2.  The dinitrogen pentoxide molecule contains only 2 moles of nitrogen and 2 moles of oxygen. It is a colorless crystal. Dinitrogen pentoxide has four covalent bonds. It is a strong oxidizer. It is heavier than air. It easily decomposes into oxygen and nitrogen dioxide. The N2O5 Compound Names are as follows: Dinitrogen pentoxide Nitrogen pentoxide Nitro nitrate Nitrogen oxide Dinitro Oxidane Nitroether

Conclusion

Dinitrogen pentoxide belongs to the NO_x species. It is an unstable and potentially dangerous oxidizing agent. It is a causative factor behind ozone layer depletion. The compound readily decomposes. In reaction with water, it gives nitric acid. Thus, it is also referred to as an anhydride of nitric acid.

Frequently Asked Questions

1. Is dinitrogen pentoxide hazardous?

Yes, dinitrogen pentoxide is a hazardous compound. Since it is a strong oxidizer, it forms explosives with ammonium salts. It readily decomposes to produce the highly toxic NO₂ gas. It also reacts with ozone and leads to ozone layer depletion.

2. How does nitrogen pentoxide occur in the atmosphere?

The atmosphere has abundant NOx species that lead to ozone depletion. Dinitrogen pentoxide is observed in the stratosphere. It reacts with aerosols and has a significant impact on the tropospheric ozone.

3. What conditions do the different structures of dinitrogen pentoxide depend on?

Dinitrogen pentoxide is a compound that has two structures based on the conditions. In the solid state, it is a salt, nitronium nitrate, with separate nitronium cations [NO2]+ and nitrate anions [NO3]−. In the gaseous phase, it occurs as a covalently-bound molecule.