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

Short answer

(a) Phosgene is formed from the oxidation of chloroform by air and light.

Step-by-step solution

Understanding the Reaction

Chloroform (CHCl₃) can undergo oxidation when exposed to light and air, particularly the oxygen in the air. This process is called photooxidation. The presence of light catalyzes the reaction, leading to the formation of another compound.

Identifying Possible Oxidation Products

The potential products listed are phosgene, formyl chloride, formaldehyde, and trichloroethanol. It's important to determine which of these is a common result of the oxidation of chloroform under the conditions given.

Analyzing the Oxidation Reaction

When chloroform is exposed to light and oxygen, it typically forms phosgene (COCl₂). Phosgene is a highly toxic gas and was historically used as a chemical warfare agent. The oxidation involves the substitution of a chlorine atom with an oxygen atom from the air, forming carbonic dichloride (phosgene).

Conclusion Based on Analysis

The oxidation of chloroform in the presence of light and air primarily produces phosgene (COCl₂). This is the most commonly observed result of such a reaction. Other options like formyl chloride, formaldehyde, and trichloroethanol are less likely in this context.

Key concepts

Photooxidation

Photooxidation is a chemical reaction that involves the interaction between a substance and oxygen in the presence of light. When it comes to chloroform, this reaction is of particular interest. - Chloroform (CHCl₃), a common solvent, begins breaking down when exposed to air and light. - The light acts as a catalyst, accelerating the reaction. - This process can result in the formation of new and often hazardous compounds. In photooxidation, the energized molecules gain enough energy to surpass the activation energy threshold. This is crucial for initiating the oxidation process, leading to more reactive intermediate species. Over time, these intermediate species can further react, creating stable end products, like phosgene. Regular monitoring of such reactions is essential because they can lead to the production of undesirable by-products.

Phosgene Formation

Phosgene, known chemically as carbonyl chloride (COCl₂), forms through the oxidation of chloroform in the presence of light and air. This reaction is significant for several reasons: - Phosgene is highly toxic and was historically utilized as a chemical warfare agent.- The formation involves the replacement of one chlorine atom from chloroform with an oxygen atom from the air.The process can be summarized as:\[ \text{CHCl}_3 + \frac{1}{2} \text{O}_2 \rightarrow \text{COCl}_2 + \text{HCl} \]Due to the dangerous nature of phosgene, this reaction underlies the importance of controlling environments where chloroform is exposed to light. Safety measures are crucial to prevent accidental exposure to this toxic compound.

Light Catalyzed Reactions

Light catalyzed reactions are reactions in which light energy functions as a catalyst to enhance chemical transformations. - In the photooxidation of chloroform, the role of light is indispensable. - Light provides the energy required for breaking the chemical bonds in chloroform, facilitating the oxidation process. The mechanism involves the absorption of photons, which excite the molecules of chloroform. With increased energy levels, these molecules become highly reactive, driving the reaction forward efficiently. This concept showcases the profound impact light has on chemical reactions. Scientists take advantage of this process in research and industrial applications, though it necessitates precautionary measures when dealing with volatile or hazardous materials like chloroform. This ensures controlled reactions and minimizes risks, especially when producing compounds such as phosgene.