Question

What product(s) is (are) expected in nitration of propane using vapours of concentrated nitric acid?
[A] 1-nitropropane
[B] 2-nitropropane
[C] nitromethane
[D] nitroethane

Answer 1

Hint: When we treat propane with excess of concentrated nitric acid, we obtain a mixture of products. The products have different yields but in total we get four different products.

Complete step by step answer:
In the question an alkane is given to us and we have to find out the products when it is reacted with the vapours of concentrated nitric acid.
When propane is reacted with fuming nitric acid i.e. the vapour of concentrated nitric acid, we obtain nitrated products. We know that such reactions are called nitration reactions and the reagent we use is the nitrating agent. Nitration of propane gives us a mixture of products. We obtain 2 nitropropene, nitroethane and nitromethane. However, the yield of the products differ from each other. We can write the reaction as-
     \[\begin{align}
  & C{{H}_{3}}C{{H}_{2}}C{{H}_{3}}+HN{{O}_{3}}\to C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}N{{O}_{2}}+C{{H}_{3}}CHN{{O}_{2}}C{{H}_{3}}+C{{H}_{3}}N{{O}_{2}}+C{{H}_{3}}C{{H}_{2}}N{{O}_{2}} \\
 & Propane\text{ }+\text{ }nitric\text{ }acid\to 1-nitropropane+2-nitropropane+nitromethane+nitroethane \\
\end{align}\]

Here, the major product that we find is 2-nitropropane and its yield is around 40%. The yield of 1-nitropropane is 25% and that of nitromethane and nitroethane is 25% and 10% respectively.
We can see from the above discussion that we obtain 1-nitropropane, 2-nitropropane, nitroethane and nitromethane from the nitration of propane.
So, the correct answer is “OptionA,B,C and D”.

Note: The nitration of alkanes is a conversion of great commercial use. Besides nitric acid, we can also use nitrogen tetra-oxide. Nitrogen tetra-oxide is also used as a nitrating agent and these reactions are carried out at a very high temperature. As we see from the above discussion that we get mixed products in this reaction, so commercially the yield and formation of products is controlled by addition of catalysts like oxygen and halogens. We use the catalysts here to raise the concentration of the alkyl radicals. However, we cannot completely control the yield of the products and the formation of the products so we generally use the process of fractional distillation for the separation of products here.