Which of the following carboxylic acids is not used in the manufacturing of soaps?

Capric acid

The correct answer is option 1. Capric acid.

In the manufacturing of soaps, fatty acids are used as the main raw materials. These fatty acids typically have long carbon chains, usually containing 12 to 18 carbon atoms. When these fatty acids react with a strong base, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), they undergo a process called saponification to form salts known as "soaps."

Let us examine the carboxylic acids mentioned:

1. Capric Acid (Decanoic Acid):

Capric acid has the chemical formula \(CH_3(CH_2)_8COOH\). It is a saturated fatty acid with a 10-carbon chain. While capric acid can be used in various applications, it is not commonly used in the manufacturing of soaps. Its shorter carbon chain may not provide the same properties and characteristics desired in soap formulations compared to longer-chain fatty acids.

2. Stearic Acid:

Stearic acid has the chemical formula \(CH_3(CH_2)_{16}COOH\). It is a saturated fatty acid with an 18-carbon chain. Stearic acid is a common ingredient in soap manufacturing. It contributes to the lathering and cleansing properties of soap and helps to stabilize the soap structure.

3. Oleic Acid:

Oleic acid has the chemical formula \(CH_3(CH_2)_7CH=CH(CH_2)_7COOH\). It is a monounsaturated fatty acid with an 18-carbon chain and one double bond \((C=C)\) between carbon atoms 9 and 10. Oleic acid is also commonly used in soap production. It helps to provide moisturizing properties and enhances the texture of the soap.

4. Palmitic Acid:

Palmitic acid has the chemical formula \(CH_3(CH_2)_{14}COOH\). It is a saturated fatty acid with a 16-carbon chain. Palmitic acid is frequently used in soap manufacturing. It contributes to the hardness and stability of the soap bar.

While stearic acid, oleic acid, and palmitic acid are commonly used in soap manufacturing due to their suitable properties and abundance in natural fats and oils, capric acid (decanoic acid) is not commonly used for soap production. This is likely because its shorter carbon chain may not provide the desired properties and characteristics expected in soaps. Additionally, capric acid may have other applications in cosmetics, pharmaceuticals, and food industries, but its use in soap manufacturing is relatively limited compared to the other options.

Therefore, when considering which carboxylic acid is not typically used in the manufacturing of soaps, capric acid (decanoic acid) is the most appropriate choice.

Therefore, the correct answer is Capric acid.