What are the tests performed to determine the presence of an amino group in an organic molecule?

The tests performed to determine the presence of an amino group in organic molecules include: litmus, solubility, carbylamine, nitrous acid, and azo-dye tests. 

In the solubility test, amines dissolve in mineral acids like hydrochloric acid, forming a salt. This indicates the compound might be an amine, but it’s not a definitive test. 

For the litmus test, since acids are basic the red litmus paper would turn blue, showing the compound is a base. This doesn’t confirm it's an amine. 

For the azo-dye test, aromatic amines react with nitrous acid to form diazonium salts, which then react with phenols (like β-naphthols) to produce an orange azo dye. This confirms the presence of aromatic amines. 

In the carbylamine test, primary amines react with chloroform and alkali to produce isocyanides (carbylamines) with a distinct odor. 

Secondary and tertiary amines do not produce this reaction. In the nitrous acid test, primary aromatic amines form diazonium salts that decompose at high temperatures. 

Primary aliphatic amines release nitrogen gas seen as bubbles, secondary amines produce a yellow oily nitrosamine, and tertiary amines form soluble nitrite salts.