The chlorinated alkane often used industrially to remove grease is?

1. Analyze the Question

The question asks for a specific chlorinated alkane that is used in industrial settings as a degreasing agent (a solvent used to dissolve oils, fats, and greases).

2. Explain the Concept

In organic chemistry, chlorinated alkanes (also known as alkyl halides) are frequently used as solvents because they are non-polar. This allows them to dissolve other non-polar substances like grease and oil, which water cannot remove.

• Tetrachloromethane ($CCl_4$): Also known as carbon tetrachloride. It is a powerful solvent historically used in dry cleaning and industrial degreasing because it is highly effective at dissolving organic compounds.
• Chloromethane ($CH_3Cl$): A gas at room temperature, used primarily as a refrigerant or in chemical synthesis, not as a degreasing solvent.
• Trichloromethane ($CHCl_3$): Also known as chloroform. While it is a solvent, it is more commonly known for its historical use as an anesthetic and in laboratory synthesis.
• Dichloromethane ($CH_2Cl_2$): Also known as methylene chloride. It is a very common solvent, but in the context of standard chemistry curricula and historical industrial applications, Tetrachloromethane is the classic answer for heavy-duty industrial degreasing.

3. Show the Solution

• Step 1: Identify the chemical properties required for a degreasing agent: it must be a non-polar solvent capable of dissolving lipids (fats/oils).
• Step 2: Evaluate the options. Tetrachloromethane ($CCl_4$) is a symmetrical, non-polar molecule with a high capacity to dissolve grease.
• Step 3: Compare with industrial standards. Tetrachloromethane was the industry standard for dry cleaning and metal degreasing for many years before its use was restricted due to toxicity and environmental concerns (ozone depletion).

4. Identify the Answer

The correct option is A.

5. Exam Tip

When you see questions about "chlorinated solvents," remember that as the number of chlorine atoms increases in a methane molecule ($CH_4 \rightarrow CH_3Cl \rightarrow CH_2Cl_2 \rightarrow CHCl_3 \rightarrow CCl_4$), the molecule becomes more non-polar and generally more effective as a solvent for non-polar substances like grease.