Question

Determine the total number of nitrogen atoms present in the reduced product obtained by reducing nitrobenzene with $LiAl{{H}_{4}}$ followed by aqueous work up.

Answer 1

Hint: Nitrobenzene (${{C}_{6}}{{H}_{5}}N{{O}_{2}}$) is an organic compound in which a nitro group is attached to a benzene ring. It is a yellow-colored liquid and has the odour of bitter almonds. These are soluble in organic solvents like ether, alcohol etc. Lithium Aluminium Hydride ($LiAl{{H}_{4}}$) is a strong reducing agent. It can reduce many compounds like carboxylic acids, aldehydes, ketones, esters, etc.

Complete Step by Step Answer:
Reduction of nitrobenzene with a strong reducing agent $LiAl{{H}_{4}}$ followed by aqueous workup results in the formation of azobenzene. The structure of azobenzene contains two phenyl groups and two doubly bonded nitrogen atoms, each bonded to one phenyl group. This means that the azobenzene has 2 nitrogen atoms.

Hence, the total number of nitrogen atoms present in the reduced product obtained by reducing nitrobenzene with $LiAl{{H}_{4}}$ followed by aqueous work up is 2.

Additional Information: $LiAl{{H}_{4}}$ is always used in dry solvents like anhydrous ether and tetrahydrofuran (THF). This is because it reacts violently with water and produces hydrogen gas. It is formed by the reaction of lithium hydride ($LiH$) with aluminium Chloride ($AlC{{l}_{3}}$). Azobenzene is orange-red in colour. It is used as a dye in various industries. It has applications in drug delivery, nonlinear optics, and rubber accelerators, etc.

Note: The lithium aluminium hydride ($LiAl{{H}_{4}}$ ) also acts as a mild oxidising agent. However, it can only reduce alcohol. It cannot reduce other compounds to alkanes.