Problem 124 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following: List I List II (Compound) \(\quad\) (Nature) 1\. Acetamide (i) Acidic 2\. Phthalimide (ii) Basic 3\. Benzonitrile (iii) Nautral 4\. Grignard reagent The correct matching is: \(\begin{array}{lll}1 & 2 & 3\end{array}\) 4 (a) (iii) (i) (i) (iii) (b) (iii) (i) (iii) (ii) (c) (i) (ii) (ii) (iii) (d) (ii) (iii) (i) (ii)

Step-by-Step Solution

Answer

The correct match is option (b): (iii), (i), (iii), (ii).

Step 1: Analyze Compound 1 - Acetamide

Acetamide is an amide, which is the product of the reaction between acetic acid and ammonia or an amine. Amides are generally neutral compounds because the nitrogen lone pair is delocalized over the carbonyl group, reducing its basicity. Therefore, acetamide is neutral.

Step 2: Analyze Compound 2 - Phthalimide

Phthalimide is a cyclic imide, which has a structure that is more acidic than simple amides because the imide hydrogen can be removed, giving it acidic properties. Therefore, phthalimide is acidic.

Step 3: Analyze Compound 3 - Benzonitrile

Benzonitrile is an aromatic nitrile. Nitriles do not exhibit acidity, and their nitrogen atom does not typically accept protons in a manner that would make them basic. Thus, benzonitrile is neutral.

Step 4: Analyze Compound 4 - Grignard Reagent

Grignard reagents, like RMgX (where R is an alkyl or aryl group and X is a halogen), are organometallic compounds that act as strong bases. They react with water and other protic substances readily to form alkanes. Therefore, Grignard reagents are basic.

Step 5: Determine the Correct Matching

From our analysis, we have: 1. Acetamide 2 (iii) Neutral 2. Phthalimide 2 (i) Acidic 3. Benzonitrile 2 (iii) Neutral 4. Grignard reagent 2 (ii) Basic This matches with option (b) given in the question.

Key Concepts

Acid-Base Properties

Understanding acid-base properties is critical in organic chemistry as it helps predict how molecules will react. Acids and bases are defined by their ability to donate or accept protons. An acid is a proton donor, while a base is a proton acceptor. Organic molecules can behave as acids or bases. For instance, in the case of phthalimide, it acts as an acid since its imide hydrogen is easily removable. This hydrogen ion (proton) donation capability gives it acidic characteristics. On the other hand, a compound like a Grignard reagent displays basic nature due to its strong tendency to accept protons during reactions. Key points about Acid-Base Properties:

• Acidic substances release protons when dissolved in water.
• Basic substances accept protons, often creating hydroxide ions in aqueous solutions.
• Neutral substances neither release nor readily accept protons.

By understanding where a molecule falls in the acid-base spectrum, chemists can better predict its reactive behavior.

Organic Compounds

Organic compounds are the backbone of organic chemistry and are primarily made up of carbon atoms bonded with elements like hydrogen, oxygen, nitrogen, and halogens. Each type imparts different properties to the compounds. Each category of organic compounds has unique features: Examples:

• Amides: Acetamide is an example and is generally neutral. This neutrality is due to the delocalization of electrons in the amide bond, which diminishes its ability to accept protons.
• Nitriles: For example, benzonitrile, do not exhibit acidity, nor do their nitrogen groups readily accept protons, making them neutral as well.
• Organometallics: Grignard reagents are a type and are known for their basic properties due to the presence of a carbon-metal bond, which interacts strongly with protons.

Understanding the types and properties of organic compounds allows chemists to predict interaction patterns and reaction pathways, which is essential for synthesizing new materials and understanding biological processes.

Chemical Reactions

Chemical reactions in organic chemistry involve the transformation of one or more organic compounds into different compounds via the making or breaking of chemical bonds. The type of reaction often depends on the properties of the compounds involved. Reactions and their Drivers:

• Acid-Base Reactions: These often involve the transfer of a proton (H⁺) and are pivotal for compounds like phthalimide which can lose an imide hydrogen to exhibit acidic behavior.
• Nucleophilic substitutions: Grignard reagents participate in these reactions, providing electrons to another molecule and accepting a proton, owing to their basic nature.

Chemical reactions in organic chemistry are governed by the properties of the reactants and are used to make new compounds or generate changes in existing substances. By understanding the underlying principles, chemists can manipulate reactions to achieve desired outcomes, such as synthesizing complex molecules or breaking down substances into simpler components.