Which of the following would not be a good choice for reducing an aryl nitro compound to an amine?

LiAlH₄-ether

The correct answer is option 4. LiAlH₄-ether.

Reducing an aryl nitro compound to an amine typically involves using reducing agents that are effective and selective for this transformation. Let's examine the options provided:

1. \(H_2/Pt\) (Hydrogen gas with platinum catalyst):

This is a common method for reducing nitro compounds to amines. It is highly effective and often used in hydrogenation reactions.

2. Fe and HCl (Iron and hydrochloric acid):

This is a classical method for reducing nitro groups to amines, known as the Bechamp reduction. It is effective and widely used in laboratory and industrial settings.

3. Sn and HCl (Tin and hydrochloric acid):

Another traditional method for reducing nitro compounds to amines, similar to the iron/HCl reduction. It is also effective and widely used.

4. \(LiAlH_4\)-ether (Lithium aluminium hydride in ether):

While \(LiAlH_4\) is a strong reducing agent, it is generally not a good choice for reducing nitro groups to amines. LiAlH4 is typically used for reducing esters, carboxylic acids, and other carbonyl compounds. In the case of nitro compounds, LiAlH4 can be too aggressive and may lead to over-reduction or side reactions, producing unwanted byproducts.

The correct answer is \(LiAlH_4\)-ether.

\(LiAlH_4\) in ether would not be a good choice for reducing an aryl nitro compound to an amine due to its overly aggressive reducing nature and the potential for producing unwanted side products.