$3^\circ$ aromatic amines: form orange hydrochloride salt of C-nitrosoamine, which liberates green C-nitrosoamine with base.

(iii) Hinsberg Test:

Separates $1^\circ, 2^\circ, 3^\circ$ amines using benzenesulfonyl chloride.
$1^\circ$ amines: $RNH_2 + C_6H_5SO_2Cl \xrightarrow{2NaOH} C_6H_5SO_2NR^-Na^+ + NaCl + 2H_2O$ (soluble), then $\xrightarrow{H^+} C_6H_5SO_2NHR$ (insoluble sulfonamide).
$2^\circ$ amines: $R_2NH + C_6H_5SO_2Cl \xrightarrow{NaOH} C_6H_5SO_2NR_2 + NaCl + H_2O$ (insoluble sulfonamide), no reaction with $H^+$.
$3^\circ$ amines: $R_3N + C_6H_5SO_2Cl \rightarrow$ quaternary ammonium sulfonate salts (soluble), then $\xrightarrow{2NaOH} C_6H_5SO_3^-Na^+ + R_3N + NaCl + H_2O$ (soluble).

(iv) Sodium Hydroxide Treatment of Ammonium Salt and Amine Salts:

Amine salts with NaOH liberate ammonia or amine.
Moistened pink litmus paper turns blue if ammonia or a volatile amine is present.

(v) Libermann's nitroso test:

Test for secondary amines.
$R_2NH + HONO \rightarrow R_2N-N=O + H_2O$ (N-nitrosoamines, yellow oils).
N-nitrosoamines + phenol + conc. $H_2SO_4 \rightarrow$ green solution, turns blue with alkali.
Tertiary amines do not react.

(i) Ninhydrin Test:
- Amino acids react with ninhydrin to give a blue or blue-violet color.
- Ammonium salts ($NH_4Cl$) give a positive test.
- Some amines (e.g., aniline) give orange to red colors (negative test).
- Proline, hydroxyproline, and 2-, 3-, 4-aminobenzoic acids give yellow color instead of blue.
(ii) Copper Complex Formation:
- Amino acids + $Cu^{2+}$ solution yields a moderate-to deep-blue liquid or a dark-blue solid copper complex.

(i) Fuming Sulfuric Acid:
- $ArH + H_2SO_4 \cdot SO_3 \rightarrow ArSO_3H + heat$
- Positive Test: Aromatic compound dissolves completely in $H_2SO_4$ with evolution of heat.
(ii) Chloroform and Aluminum Chloride:
- $3ArH + CHCl_3 \xrightarrow{AlCl_3} Ar_3CH + 3HCl$
- $Ar_3CH + R^+ \rightarrow Ar_3C^+ + RH$ (colored)
- Positive Test: Aromatics give colored solution or powder (orange, red, blue, purple, green).
- Non-aromatics give yellow color (negative result).
(iii) Azoxybenzene and Aluminum Chloride:
- Color of solution/precipitate depends on functional groups.
- Aromatic hydrocarbons and halogen derivatives produce deep-orange to dark-red color.
- Fused aromatic rings (naphthalene, anthracene) produce brown color.
- Aliphatic hydrocarbons give no color or pale yellow.

Ethers are less polar and slightly more reactive than saturated hydrocarbons or alkyl halides.
Form explosive peroxides upon standing (especially with air/light exposure).
Liquid ethers with solid precipitates should not be handled.
(i) Hydroiodic Acid (Zeisel's, Alkoxyl method):
- $R'OR + 2HI \rightarrow R'I + RI + H_2O$
- $ArOR + HI \rightarrow RI + ArOH$
- $Hg(NO_3)_2 + 2R'I \rightarrow HgI_2 + 2R'OH + 2HNO_3$
- Positive Test: Orange