Nitration

Nitration is a general class of chemical processes for the introduction of a nitro group into an organic chemical compound.

Nitration vs nitrate esters

More loosely the term also is applied incorrectly to the different process of forming nitrate esters between alcohols and nitric acid, as occurs in the synthesis of nitroglycerin and nitrocellulose. The difference between the resulting structure of nitro compounds and nitrates is that the nitrogen atom in nitro compounds is directly bonded to a non-oxygen atom, typically carbon or another nitrogen atom, whereas in nitrate esters the nitrogen is bonded to an oxygen atom that in turn is bonded to a carbon atom.

Aliphatic nitration

Free radical aliphatic nitration occurs at very high temperatures, in gas phase, between alkanes and nitric acid or dinitrogen tetroxide. The reaction produces a variety of nitro compounds, the ratio depends on the catalysts used (or not used).

For example, the nitration of propane is done at 425 °C using nitric acid. The reaction produces 4 main products: 1-nitropropane (25%), 2-nitropropane (40%), nitroethane (10%) and nitromethane (25%).

C₃H₈ + HNO₃ → CH₃CH₂CH₂NO₂ + CH₃CH(NO₂)CH₃ + CH₃CH₂NO₂ + CH₃NO₂

All the products are separated using fractional distillation.

Aromatic nitration

Typical nitration syntheses use a mixture of concentrated nitric acid and sulfuric acids, called nitrating mixture or mixed acid. This mixture produces the nitronium ion (NO₂⁺), which is the active species in aromatic nitration. A more stable source of nitronium ion is nitronium tetrafluoroborate, which can replace the nitrating mixture. In mixed-acid syntheses, sulfuric acid is not consumed and acts as a catalyst as well as an absorbent for water.

Projects

• Make nitromethane
• Make nitrobenzene
• Make energetic materials (TNT, etc.)

Safety

Nitrating organic compounds is a dangerous procedure that uses corrosive oxidizing mixtures. Proper protection must be worn at all times. Temperature control is important, as some compounds may decompose if the reaction temperature is too high.

See also

• Wolffenstein–Böters reaction

References

Relevant Sciencemadness threads

• Wich salt makes the most attractive nitration mix with H2SO4?
• Nitration Calculations
• nitration without sulfuric acid
• Nitration without sulfuric acid?
• Olah's Nitration Book
• Nitration of Propenylbenzenes
• abnormal nitration of styrene
• Nitration of phthalic acid
• Aromatic nitration with Guanidine Nitrate
• Toluene Nitration Using Nitrate Salts
• Nitration of hexamine via patent 3981975?
• Nitration of xylene
• Ortho Nitration