Question

The compound that does not liberate \(\mathrm{CO}_{2}\) on treatment with aqueous sodium bicarbonate solution is (A) Benzoic acid (B) Benzenesulphonic acid (C) Salicylic acid (D) Carbolic acid (phenol)

Short answer

The compound that does not liberate CO2 on treatment with aqueous sodium bicarbonate solution is (D) Carbolic acid (phenol). This is because phenols are weaker acids compared to the other given compounds and do not react with sodium bicarbonate under the same conditions.

Step-by-step solution

Identify the given compounds and their chemical structures

First, let's list down the given compounds and their chemical structures/formulas: (A) Benzoic acid: \(C_7H_6O_2\) (B) Benzenesulphonic acid: \(C_6H_5SO_3H\) (C) Salicylic acid: \(C_7H_6O_3\) (D) Carbolic acid (phenol): \(C_6H_5OH\)

Understand the reaction of acids with aqueous sodium bicarbonate

Aqueous sodium bicarbonate (\(NaHCO_3\)) reacts with acidic substances and liberates CO2 gas. Generally, compounds with an acidic hydrogen atom can generate carbon dioxide gas with sodium bicarbonate by the following generic reaction: Acid + \(NaHCO_3\) -> Salt + CO2 + H2O Now, let's analyze the given compound's reaction with sodium bicarbonate to determine which does not produce CO2 gas.

Analyze the reactions of the given compounds with sodium bicarbonate

(A) Benzoic acid (carboxylic acid) reacts with sodium bicarbonate to produce benzoate salt, CO2, and water as shown: \(C_7H_6O_2\) + \(NaHCO_3\) -> \(C_7H_5O_2Na\) + CO2 + H2O (B) Benzenesulphonic acid (sulfonic acid) reacts with sodium bicarbonate to produce the benzenesulfonate salt, CO2, and water as shown: \(C_6H_5SO_3H\) + \(NaHCO_3\) -> \(C_6H_5SO_3Na\) + CO2 + H2O (C) Salicylic acid (carboxylic acid) reacts with sodium bicarbonate to produce salicylate salt, CO2, and water as shown: \(C_7H_6O_3\) + \(NaHCO_3\) -> \(C_7H_5O_3Na\) + CO2 + H2O (D) Carbolic acid (phenol) has only acidic hydrogen atoms on its hydroxyl group; however, the acidity is weaker than that of the other given compounds (carboxylic and sulfonic acids). Thus, it will not react with sodium bicarbonate to produce CO2 gas, as the reaction conditions are not sufficient for the reaction to proceed. Phenols do not react with sodium bicarbonate under the same conditions as carboxylic and sulfonic acids as they are weaker acids.

Answer the question

Since only Carbolic acid (phenol) does not liberate CO2 gas on treatment with aqueous sodium bicarbonate solution, the correct answer is: (D) Carbolic acid (phenol)

Key concepts

Organic Chemistry

Organic chemistry is a branch of chemistry that deals with carbon-containing compounds. These compounds often involve carbon atoms bonded to hydrogen, oxygen, nitrogen, and other elements.
Organic molecules can vary widely, from simple structures like methane ( CH₄ ) to complex structures such as proteins and DNA.

• Carbon's ability to form stable bonds with other elements allows for diverse chemical structures.
• This diversity leads to vast possibilities in the behavior and reactivity of organic compounds.
• Organic reactions often involve functional groups, like alcohols, acids, and amines.

Understanding these reactions helps us predict how compounds will interact, crucial for fields like pharmaceuticals, agriculture, and materials science.

Carboxylic Acids

Carboxylic acids are a group of organic acids that contain a carboxyl group ( -COOH ). They are known for their acidic properties, attributed to their ability to donate a proton ( H⁺ ).

• The carboxyl group consists of a carbonyl group ( C=O ) and a hydroxyl group ( -OH ).
• These acids are generally weak acids, but stronger than phenols and alcohols.
• Common examples include acetic acid (vinegar) and benzoic acid, both reacting vigorously with sodium bicarbonate to release carbon dioxide.

Carboxylic acids' acidity is strong enough to allow them to react with bases like sodium bicarbonate, an important property in differentiating them from weaker acids, such as phenols.

Sulfonic Acids

Sulfonic acids are another group of strong organic acids. They contain the sulfonic group ( -SO₃H ), where the sulfur atom is bonded to three oxygen atoms, one of which has a double bond.

• Sulfonic acids are stronger than carboxylic acids, due to greater resonance stabilization of the sulfonate ion.
• They are highly reactive and form salts during reactions with bases.
• Benzenesulphonic acid is a common example, reacting with sodium bicarbonate to liberate CO₂ gas.

Their strong acidic nature makes them suitable as catalysts and detergents, as well as for use in various cleaning agents.

Phenols

Phenols are a type of organic compound characterized by a hydroxyl group ( -OH ) bonded directly to an aromatic hydrocarbon group, like benzene.

• Phenols are less acidic than carboxylic and sulfonic acids because the phenoxide ion is less stable.
• This lower acidity results in phenols not reacting with sodium bicarbonate to produce CO₂ under normal conditions.
• Carbolic acid, a common name for phenol, illustrates this weak acidity.

The unique structure of phenols gives them special properties, such as antiseptic qualities, making them valuable in both industrial and medical applications.

Sodium Bicarbonate

Sodium bicarbonate ( NaHCO₃ ), commonly known as baking soda, is a versatile compound with various applications in both household and industrial settings.

• It acts as a mild base, reacting with acids to produce carbon dioxide gas, salt, and water.
• This reaction is visible in baking, where it helps dough rise.
• Its reactivity with carboxylic and sulfonic acids but not phenols is a key property used in chemical analysis.

In organic chemistry, sodium bicarbonate serves as a tool to test the acidity of compounds, offering insights into their chemical nature and behavior.