Question

Aniline is usually purified by: (a) Chromatography technique (b) By addition of oxalic acid (c) Fractional crystallization (d) Steam distillation

Short answer

Aniline is usually purified by steam distillation.

Step-by-step solution

Understanding Aniline Purification

Aniline is an organic compound used as a base for dyes and chemicals, which often needs purification. Among the given options, certain methods are more suitable due to aniline's chemical and physical properties.

Identifying Suitable Methods

Consider each method in the context of aniline: (a) Chromatography is generally used for separating substances from mixtures based on differences in adsorption. (b) Addition of oxalic acid would form a salt (anilinium oxalate) with aniline, making it impure and needing further extraction. (c) Fractional crystallization might not be practical as aniline doesn't form solid crystals at room temperature. (d) Steam distillation is effective for purifying heat-sensitive organic compounds that have a tendency to decompose or polymerize.

Selecting the Most Appropriate Method

Steam distillation is commonly used for purifying aniline since it can help separate volatile compounds without decomposition. Aniline doesn't crystallize significantly and isn't effectively purified by chromatography or addition of acids without introducing impurities.

Key concepts

Steam Distillation

Steam distillation is a powerful technique used to purify heat-sensitive organic compounds. It works by leveraging the fact that some substances can be vaporized at temperatures below their boiling points, using the addition of steam. This method is particularly useful for compounds that may decompose at higher temperatures.

In the process, steam is introduced into a container holding the substance. The temperature is carefully controlled so that the compound vaporizes along with water. This allows for the separation of volatile components from non-volatile ones.

• Steam distillation is advantageous for aniline because it prevents thermal decomposition, ensuring purity.
• It's efficient and cost-effective, making it a staple in organic chemistry laboratories.
• This method also allows for the collection of distillates, which can be easily separated and purified further if needed.

By enabling purification at lower temperatures, steam distillation provides a safe and efficient way to handle delicate compounds such as aniline.

Organic Chemistry

Organic chemistry is the branch of chemistry that deals with the study of compounds containing carbon. These carbon-containing compounds are classified based on their structures and functional groups. Aniline, for instance, is an aromatic compound characterized by a benzene ring linked to an amino group.

Aniline’s role in organic chemistry cannot be overstated. It forms the foundation for more complex molecules and serves as a crucial industrial chemical in the production of dyes and pharmaceuticals.

• Understanding organic chemistry is vital for comprehending how different purification techniques affect compounds like aniline.
• Organic chemistry principles help predict the behavior of compounds under various conditions.
• Recognizing the structure and properties of compounds aids in selecting appropriate purification methods, like steam distillation.

By learning the basics of organic chemistry, you can better appreciate intricate reactions and why certain methods are preferred for specific compounds.

Separation Techniques

In chemistry, separation techniques are processes used to divide mixtures into their individual components. They play an indispensable role in analysis and purification, especially in organic chemistry where many substances coexist in mixtures.

Different methods are selected based on the properties of the substances involved, such as their boiling points, solubilities, and structural features.

• Steam distillation is one such technique that separates substances by boiling them with steam, efficient for temperature-sensitive materials.
• Chromatography, another method, segregates compounds based on their differential adsorption properties.
• Crystallization relies on differences in solubility to separate solids from liquids.

The right separation technique is crucial to achieving the desired purity and efficiency. Understanding the characteristics of the compounds involved helps in choosing the best method for their separation and purification.

Aniline Properties

Aniline is a crucial organic compound with several distinctive properties that influence its purification methods. Its molecular structure consists of a benzene ring attached to an amino group, which defines its chemical behavior.

Here are some key properties of aniline that affect its purification:

• Boiling Point: Aniline has a high boiling point, making simple distillation inefficient. Steam distillation is preferred because it lowers the effective boiling point by using steam.
• Solubility: It has limited solubility in water but is soluble in organic solvents, which influences the choice of separation techniques.
• Reactivity: Aniline can easily react with acids to form anilinium salt, meaning care must be taken to avoid unnecessary reactions during purification.

Aniline’s properties, such as its interaction with acids, its boiling point, and solubility, are vital in determining the most suitable purification method. These attributes underscore why steam distillation is so beneficial for purifying aniline without causing decomposition.