Problem 49 - Chemistry The Central Science

Question

Draw the condensed structure of the compounds formed by condensation reactions between (a) benzoic acid and ethanol, (b) ethanoic acid and methylamine, (c) acetic acid and phenol. Name the compound in each case.

Step-by-Step Solution

Answer

(a) The condensed structure of the product formed by the reaction of benzoic acid and ethanol is C6H5COOCH2CH3, and the name of this compound is ethyl benzoate. (b) The condensed structure of the product formed by the reaction of ethanoic acid and methylamine is CH3CONHCH3, and the name of this compound is N-methylacetamide. (c) The condensed structure of the product formed by the reaction of acetic acid and phenol is CH3COOC6H5, and the name of this compound is phenyl acetate.

Step 1: (a) Condensation reaction of benzoic acid and ethanol

To find the condensed structure of the product formed in the condensation reaction between benzoic acid and ethanol, first, identify the functional groups present in the reactants and predict the site of the reaction. Benzoic acid has a carboxylic acid functional group (-COOH), and ethanol has an alcohol functional group (-OH). In a condensation reaction between a carboxylic acid and an alcohol, an ester is formed with the elimination of water. Condensed structure of benzoic acid: C6H5COOH Condensed structure of ethanol: CH3CH2OH Now, combine the reactants and eliminate a water molecule (H2O) to form an ester.

Step 2: Condensed structure and name of the product (a)

The condensed structure of the product formed by the reaction of benzoic acid and ethanol is C6H5COOCH2CH3. The name of this compound is ethyl benzoate.

Step 3: (b) Condensation reaction of ethanoic acid and methylamine

To find the condensed structure of the product formed in the condensation reaction between ethanoic acid and methylamine, first identify the functional groups present in the reactants and predict the site of the reaction. Ethanoic acid has a carboxylic acid functional group (-COOH), and methylamine has an amine functional group (-NH2). In a condensation reaction between a carboxylic acid and an amine, an amide is formed with the elimination of water. Condensed structure of ethanoic acid: CH3COOH Condensed structure of methylamine: CH3NH2 Now, combine the reactants and eliminate a water molecule (H2O) to form an amide.

Step 4: Condensed structure and name of the product (b)

The condensed structure of the product formed by the reaction of ethanoic acid and methylamine is CH3CONHCH3. The name of this compound is N-methylacetamide.

Step 5: (c) Condensation reaction of acetic acid and phenol

To find the condensed structure of the product formed in the condensation reaction between acetic acid and phenol, first identify the functional groups present in the reactants and predict the site of the reaction. Acetic acid has a carboxylic acid functional group (-COOH), and phenol has an alcohol functional group (-OH). In a condensation reaction between a carboxylic acid and an alcohol, an ester is formed with the elimination of water. Condensed structure of acetic acid: CH3COOH Condensed structure of phenol: C6H5OH Now, combine the reactants and eliminate a water molecule (H2O) to form an ester.

Step 6: Condensed structure and name of the product (c)

The condensed structure of the product formed by the reaction of acetic acid and phenol is CH3COOC6H5. The name of this compound is phenyl acetate.

Key Concepts

Ester Formation

Ester formation is a key process in organic chemistry where a carboxylic acid reacts with an alcohol to form an ester. This reaction is called a condensation reaction, as it involves the loss of a water molecule.

• Reacting Molecules: A carboxylic acid, which has the functional group -COOH, and an alcohol, which possesses an -OH functional group, come together in this process.
• Product of Reaction: The result is an ester, characterized by the -COO- functional group.
• Water Elimination: During the reaction, the hydroxyl group (-OH) from the carboxylic acid and the hydrogen atom from the alcohol's -OH group combine to form water (H₂O), which is eliminated, leaving behind an ester linkage.

This type of reaction is frequently used in the creation of fragrances, flavoring agents, and lipids.

Amide Formation

Amide formation occurs when a carboxylic acid reacts with an amine. This reaction also belongs to the family of condensation reactions, as it releases water as a byproduct.

• Reacting Participants: A carboxylic acid (-COOH) and an amine (-NH₂) are the starting materials.
• Outcome: The resulting compound is an amide, characterized by the presence of a -CONH- group.
• Water Byproduct: Similar to esterification, this reaction involves the removal of a water molecule, which is formed by the hydroxyl part of the carboxylic acid and a hydrogen from the amine group's -NH₂.

Amides are commonly found in proteins and synthetic materials like nylon.

Functional Groups

In organic chemistry, functional groups are the specific groups of atoms responsible for the characteristic chemical reactions of those molecules.

• Role: They define how a molecule reacts with different substances. The behavior in reactions is often predictable if the functional groups are known.
• Examples: Common functional groups include alcohols (-OH), carboxylic acids (-COOH), amines (-NH₂), and esters (-COO-).

These groups are pivotal in understanding chemical reactivity and properties of organic molecules, guiding synthetic chemists in designing and predicting organic reactions.

Carboxylic Acid

Carboxylic acids are organic compounds characterized by the presence of the carboxyl functional group, -COOH. These acids are highly versatile and serve as precursors in many chemical reactions.

• Structure: The carboxyl group consists of a carbon double-bonded to an oxygen and single-bonded to a hydroxyl group (-OH).
• Behavior: Carboxylic acids are known for their acidic properties, which arise from their ability to donate the hydrogen ion from the -OH group.

They play a key role in the formation of esters and amides, acting as a primary participant in these reactions.

Alcohol

Alcohols are a widely known group of compounds with a hydroxyl group (-OH) attached to a saturated carbon atom.

• Chemical Characteristics: Alcohols are polar due to the electronegative oxygen atom, making them capable of participating in hydrogen bonding.
• Reactivity: In esterification, the -OH group of an alcohol reacts with the -COOH group of a carboxylic acid, producing esters and water.

Common alcohols like ethanol are used in beverages, antiseptics, and as intermediates in industrial chemical processes.

Amine

Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. They are derived from ammonia and have significant roles in chemical reactions.

• Structure and Types: Amines can be primary (-NH₂), secondary, or tertiary, based on the number of carbon-containing groups attached to the nitrogen.
• Importance in Amide Formation: Amines play a crucial role in forming amides through their reaction with carboxylic acids, losing a hydrogen atom in the process of condensation.

Amines are building blocks for proteins and are essential in pharmaceutical chemistry.

Water Elimination

Water elimination is a critical component of condensation reactions. It is the process through which a water molecule is lost during the transformation of functional groups like esters and amides.

• Mechanism: The reaction involves the removal of an -OH group from one molecule and a hydrogen atom from another, forming H₂O.
• Role in Reactions: This step is central in both esterification and amide formation, transforming the reactants into new functional groups.

This concept is pivotal in understanding how larger, more complex organic molecules are synthesized by assembling smaller subunits.