Class 12 Chemistry Lab Manual – Preparation of Organic Compounds

Preparation of organic compounds is a significant part of Class 12 Chemistry practicals. These experiments involve the synthesis of simple organic compounds through well-defined reactions such as acetylation, esterification, or oxidation. Performing organic synthesis helps students understand reaction mechanisms, purification techniques, and the concept of yield and purity. Practical examinations, conducted under the supervision of the Central Board of Secondary Education, evaluate students on their ability to perform experiments accurately, record observations systematically, and answer viva questions confidently.

Practical knowledge in the preparation of organic compounds builds laboratory skills, observation accuracy, and understanding of reaction mechanisms. Studentbro.in provides a structured, step-by-step, and exam-oriented guide to help Class 12 students master organic synthesis experiments.

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Importance of Preparing Organic Compounds in Practical Experiments

Studying the preparation of organic compounds in the laboratory allows students to:

• Understand organic reaction types such as acetylation, esterification, and oxidation

• Learn purification techniques including crystallization and recrystallization

• Develop skills in handling flammable solvents and reagents safely

• Enhance analytical, observation, and recording skills

• Connect theoretical reaction mechanisms with practical outcomes

Hands-on experience ensures better comprehension of organic chemistry and prepares students for practical examinations.

Objectives of Preparation of Organic Compounds Experiments

The main objectives include:

• To synthesize simple organic compounds from given reactants

• To purify the products using crystallization or recrystallization

• To determine the percentage yield and melting point of the compounds

• To observe and record physical properties of the synthesized compounds

• To develop precision in handling apparatus, solvents, and reagents

Achieving these objectives ensures a comprehensive understanding of laboratory techniques in organic chemistry.

Principles of Preparation of Organic Compounds Experiments

These experiments are based on the following principles:

• Reaction Mechanism – Understanding how reactants convert into products via chemical reactions

• Purification – Techniques like crystallization or recrystallization to obtain pure compounds

• Stoichiometry – Accurate measurement of reactants for complete reactions

• Yield and Purity – Assessing the amount of product obtained and its quality

• Safety – Proper handling of flammable and corrosive reagents

Understanding these principles ensures correct execution of experiments and accurate results.

Common Experiments in Preparation of Organic Compounds

1. Preparation of Acetanilide

   • Principle: Acetylation of aniline with acetic anhydride produces acetanilide.

   • Apparatus: Beakers, conical flask, glass rod, water bath, filter paper, watch glass, funnel, aniline, acetic anhydride.

   • Procedure: Mix reactants, heat gently in water bath, cool, filter, wash and dry the crystals.

   • Observation: Formation of white crystalline solid; record melting point and yield.

2. Preparation of Aspirin (Acetylsalicylic Acid)

   • Principle: Esterification of salicylic acid with acetic anhydride produces aspirin.

   • Apparatus: Conical flask, glass rod, beaker, filter paper, watch glass, funnel, salicylic acid, acetic anhydride, catalyst (H₂SO₄).

   • Procedure: Mix reactants, heat, cool, crystallize product, filter and dry.

   • Observation: White crystalline product; measure melting point and yield.

3. Preparation of Oxalic Acid from Sugar

   • Principle: Oxidation of sugar with concentrated H₂SO₄ produces oxalic acid.

   • Apparatus: Conical flask, beakers, filter paper, funnel, stirring rod, sugar, H₂SO₄, water, KI solution.

   • Procedure: Mix sugar and concentrated sulfuric acid, add water, filter, and purify crystals.

   • Observation: White crystalline solid; record melting point and yield.

4. Preparation of Nylon 6,6 (Optional Industrial Organic Synthesis)

   • Principle: Condensation polymerization between adipoyl chloride and hexamethylenediamine produces nylon.

   • Apparatus: Beakers, glass rods, funnel, distilled water, adipoyl chloride, hexamethylenediamine.

   • Procedure: Carefully layer the two reactants, observe formation of polymer at interface, pull nylon thread.

   • Observation: Formation of continuous polymer thread; note observations on color and texture.

These experiments provide practical understanding of reaction mechanisms, purification techniques, and analysis of organic compounds.

Apparatus Required for Preparation of Organic Compounds

• Beakers, conical flasks, and measuring cylinders

• Water bath for heating reactions

• Glass rods and stirrers

• Funnels and filter paper

• Watch glass and evaporating dishes

• Chemicals: aniline, acetic anhydride, salicylic acid, concentrated acids, sugar, solvents

• Safety equipment: gloves, goggles, lab coat, fume hood

Familiarity with apparatus ensures safe handling and accurate results.

Experimental Setup

• Place apparatus on a stable and clean surface

• Measure all reactants accurately

• Use water bath for controlled heating

• Stir gently to avoid spillage

• Allow crystals to form slowly for purity

• Filter and dry the product carefully

• Properly label all solutions and samples

A systematic setup ensures reliable and reproducible results.

Observation Tables and Recording Results

Observation tables include:

• Name of compound prepared

• Physical appearance (color, shape, crystalline form)

• Mass of product obtained

• Reaction conditions (temperature, duration)

• Yield and melting point

• Notes on purity or impurities

Systematic recording is essential for analysis and viva preparation.

Calculations and Results

Students should:

• Calculate percentage yield using:

Percentage Yield=Actual YieldTheoretical Yield×100\text{Percentage Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100Percentage Yield=Theoretical YieldActual Yield​×100

• Record melting point and physical characteristics

• Compare experimental yield with theoretical expectations

• Present step-by-step calculations for clarity

Accurate calculations reinforce understanding of organic synthesis and practical chemistry.

Precautions for Preparation of Organic Compounds Experiments

• Handle flammable and corrosive reagents carefully

• Use a water bath for controlled heating

• Measure chemicals accurately

• Avoid rapid crystallization to ensure pure product

• Wear gloves, goggles, and lab coat

• Work in a well-ventilated area or fume hood

Precautions ensure safety, accuracy, and reproducibility.

Common Mistakes to Avoid

• Overheating or underheating reactions

• Using impure or incorrect reagents

• Disturbing crystals during formation

• Improper filtration leading to contamination

• Neglecting safety precautions

Avoiding mistakes ensures reliable results and high marks.

Viva Questions on Preparation of Organic Compounds

• Explain the principle of acetylation or esterification

• How do you purify organic compounds?

• How is percentage yield calculated?

• What are the factors affecting crystallization?

• Explain the reaction involved in preparation of aspirin

• What safety precautions are necessary for organic synthesis?

Viva preparation ensures confident responses during practical exams.

Marking Scheme for Organic Compounds Practical

Marks are awarded based on:

• Correct experimental setup and procedure

• Accuracy in measurements and reaction execution

• Purity, appearance, and yield of product

• Neat diagrams and recorded tables

• Completion of practical record

• Viva answers

A complete and well-documented report ensures maximum marks.

Applications of Preparation of Organic Compounds

Organic synthesis experiments are useful in:

• Pharmaceutical and medicinal chemistry for drug synthesis

• Industrial preparation of important chemicals

• Laboratory preparation for research and education

• Understanding reaction mechanisms and organic chemistry principles

• Connecting theory with real-world chemical applications

Practical knowledge equips students to understand and apply organic chemistry concepts.

How Studentbro.in Supports Class 12 Chemistry Students

Studentbro.in provides:

• Step-by-step guidance for preparation of organic compounds

• Apparatus handling and setup instructions

• Observation table templates and calculation examples

• Viva question bank and preparation strategies

• Safety and precaution tips aligned with CBSE syllabus

Our resources equip students with structured, reliable, and exam-focused preparation.

Conclusion

Preparation of organic compounds experiments is essential for understanding reaction mechanisms, purification, and practical laboratory skills. Accurate measurement, systematic observation, careful handling of reagents, and proper calculation are key to performing well in practical examinations.

By following CBSE guidelines and regular practice, students can confidently perform organic compound preparation experiments and achieve excellent results.

Studentbro.in provides comprehensive, easy-to-understand, and exam-oriented resources to support Class 12 students in mastering Chemistry practicals.