Experiment 189

Objective

To identify the presence of sulphanamide in an unknown organic sample.

Introduction

This experiment includes the analysis of physical properties, solubility testing, and functional group tests to systematically identify the unknown compound. The melting point is compared with known values to confirm its identity.

Physical Characteristics of Sample:

●      Color: White

●      State: Not specified

●      Melting Point: 166.5°C

Solubility Test Results

Materials

Chemicals

●       Unknown organic sample (presumed sulphanamide)

●       Distilled water

●       5% HCl, 5% NaOH, 5% NaHCO₃

●       Ferrous sulfate, Nitric acid

●       Silver nitrate, Ferric chloride

●       10% NaNO₂, 2% bromine solution

Apparatus

●       Test tubes and holder

●       Bunsen burner

●       Thermometer

●       500 mL flask, test tube stand

●       Pipette

●       Fusion tube

●       Mortar and pestle

Preparation of Reagents

●       Prepare solutions of 5% HCl, 5% NaOH, 5% NaHCO₃, and 5% ferrous sulfate in a 500 mL flask.

●       Prepare a 10% NaNO₂ solution and a 20% NaOH solution for specific tests.

Procedure

1.    Elementary Analysis (Stock Solution Preparation)

●       Heat a piece of sodium in a fusion tube until molten.

●       Add a small amount of the sample, heat to a dull red, then drop the tube into a mortar with 3-5 mL of distilled water.

●       Crush the tube, filter the solution, and use it for further testing.

●       Test for Nitrogen: Add 1-2 mL of the stock solution to freshly prepared ferrous sulfate, boil, cool, and add a few drops of H₂SO₄.

●      Observation: Prussian blue indicates nitrogen is present.

●       Test for Halogens: Acidify 1 mL of boiling solution with nitric acid, boil, cool, and add silver nitrate.

●      Observation: Absence of white, pale yellow, or yellow precipitate indicates no halogens (Cl, Br, I).

●       Test for Sulfur: Acidify 1 mL of solution with acetic acid and add lead acetate.

●      Observation: Black precipitate indicates sulfur is present.

●       Test for Nitrogen and Sulfur Together: Acidify 1 mL of the stock solution with HCl, then add FeCl₃.

●      Observation: Blood red color confirms the presence of both nitrogen and sulfur.

2.    Functional Group Tests

●       Test for Unsaturation: Dissolve 0.2 g of the sample in CCl₄, then add bromine solution.

●      Observation: Discharge of bromine color indicates unsaturation.

●       Primary Amine (-NH₂): Dissolve sample in dilute HCl, add NaNO₂, and transfer to an alkaline α-naphthol solution.

●      Observation: Orange-red precipitate confirms -NH₂.

●       Secondary Amine (-NH-): Add excess NaNO₂ to a sample in dilute HCl.

●      Observation: No oily liquid forms, indicating secondary amine is absent.

●       Tertiary Amine (=N-): Add NaNO₂ to a sample in dilute HCl, heat with NaOH.

●      Observation: No green crystals form, indicating tertiary amine is absent.

●       Substituted Amide (-NHCOR): Boil with HCl, cool, and add to an alkaline α-naphthol solution.

●      Observation: No orange-red precipitate, indicating -NHCOR is absent.

●       Nitro Group (-NO₃): Boil with tin and HCl, cool, dilute with water, and add NaNO₂.

●      Observation: No orange-red precipitate, indicating -NO₃ group is absent.

●       Carbonyl Group (=C=O): Dissolve in rectified spirit, add 2,4-DNPH.

●      Observation: No orange-red precipitate, indicating carbonyl group is absent.

●       Carboxylic Acid (-COOH): Add sample to NaHCO₃ solution.

●      Observation: No reaction, indicating -COOH is absent.

●       Phenol Group (Ar-OH): Dissolve in rectified spirit, add FeCl₃.

●      Observation: No intense coloration, indicating phenol group is absent.

●       Aromatic Hydrocarbon: Dissolve in absolute alcohol, add picric acid solution.

●      Observation: Orange-red needle-shaped crystals confirm aromatic hydrocarbon.

Observation

Identified Functional Groups:

●       Elements: Nitrogen (N) and Sulfur (S)

●       Functional Groups: Primary amine (-NH₂)

Based on the melting point of 166.5°C and the presence of these functional groups, the sample is identified as sulphanamide.

Questions

1.    What is sulphanamide?

2.    Which groups are contained in sulphanamide?

3.    What is the Lassaigne test?

4.    What elements are found in sulphanamide?

5.    What are sulfa drugs?