Problem 64 - A Complete Resource Book in Chemistry for JEE Main

Question

Chloroform is slowly oxidized by air in the presence of light and air to form (a) phosgene (b) formyl chloride (c) formaldehyde (d) trichloroethanol

Step-by-Step Solution

Answer

The oxidation of chloroform in the presence of light and air forms (a) phosgene.

Step 1: Understanding the Chemical Reaction

Chloroform ( CCl_3) is known to undergo oxidation when exposed to light and air (specifically oxygen in the air). Identify that the presence of light facilitates the oxidation process.

Step 2: Recognize Common Product of Chloroform Oxidation

When chloroform is oxidized in the presence of air and light, the most common product formed is phosgene (COCl2). Historically, this reaction is well-documented due to the toxicity of phosgene, which is why chloroform needs to be stored in dark bottles.

Step 3: Knowledge of Incorrect Options

Formyl chloride, formaldehyde, and trichloroethanol are possibilities in other reactions involving chlorinated compounds but are not typically formed directly from the oxidation of chloroform under these conditions.

Key Concepts

Phosgene formation

Phosgene is a chemical compound with the formula \( \text{COCl}_2 \). It is a colorless gas with a suffocating odor. This compound is a crucial part of the chemical industry, often used in the production of dyes, pharmaceuticals, and pesticides. However, its formation as a result of chloroform oxidation is a matter of significant concern because of its high toxicity.
Chloroform is known to undergo oxidation in the presence of light and air, resulting in the formation of phosgene. The chemical reaction involves chloroform \( (\text{CHCl}_3) \) being exposed to oxygen in the air, catalyzed by the presence of light, leading to the breakdown of the chloroform molecule into phosgene.

• It's crucial to store chloroform away from light to prevent this dangerous chemical reaction.
• Phosgene was historically used as a chemical warfare agent due to its toxicity, making awareness of its potential formation critical.

Chemical reaction analysis

Chemical reaction analysis involves breaking down the processes and conditions under which chemical reactions occur, allowing us to understand the mechanisms involved. With chloroform oxidation, several elements are vital to analyze.

First, the role of light is critical. Light provides the energy required to break the bonds in chloroform, facilitating the introduction of oxygen atoms into the chemical structure. Without light, the oxidation of chloroform is significantly slow or nearly halted.

• The presence of air, particularly oxygen, provides the necessary molecules for the oxidation process.
• The chemical stability and reactivity of chloroform in light and air signify important factors that chemists must consider, especially in laboratory and industrial settings.

Understanding these elements can help us take preventative measures when handling chloroform, ensuring both safety and efficiency in chemical processes.

Chloroform safety

The safety measures associated with handling chloroform are vitally important due to the potential hazards linked with its oxidation to phosgene. Chloroform should always be stored and handled in conditions that minimize the risk of unwanted chemical reactions.
Here are some key safety considerations:

• Store chloroform in dark, tightly-sealed bottles to reduce exposure to light and air.
• Implement adequate ventilation in areas handling chloroform to prevent accumulation of any harmful gases.
• Use personal protective equipment like gloves and goggles when working with chloroform to minimize skin and eye exposure.

By following these precautions, the risks associated with chloroform oxidation can be effectively controlled, ensuring a safer environment both in laboratory settings and any industrial applications.