Question

Which among the following options is incorrect? (A) \(1 \%\) ethanol is added in chloroform to convert poisonous \(\mathrm{COCl}_{2}\) into nonpoisonous diethyl carbonate CCOC(=O)OCC(=O)Cl (B) \(\mathrm{CHCl}_{3} \stackrel{\mathrm{HNO}_{3}}{\longrightarrow} \mathrm{CCl}_{3}-\mathrm{NO}_{2}\) (Chloropicrin) (C) \(\mathrm{CHCl}_{3} \stackrel{\mathrm{CH}_{3} \mathrm{COCH}_{1}}{\longrightarrow}\) CC(C)(O)C(C)(Cl)Cl (Chloretone) (D) \(\mathrm{CHCl}_{3} \stackrel{\mathrm{Ag}(\mathrm{s})}{\longrightarrow} \mathrm{CH}_{2}=\mathrm{CH}_{2}\)

Short answer

Option D is incorrect since the dehalogenation of chloroform with silver to form ethene is not plausible. The given reaction cannot occur using only silver.

Step-by-step solution

Option A: Conversion of COCl2 to diethyl carbonate

In this case, 1% ethanol is added to chloroform to convert poisonous COCl2 (phosgene) into non-poisonous diethyl carbonate. The reaction is as follows: \[ COCl_2 + 2CH_3CH_2OH \longrightarrow (CH_3CH_2O)_2CO + 2HCl \] The reaction is accurate and represents the production of diethyl carbonate from phosgene and ethanol. Hence, Option A is correct.

Option B: Formation of Chloropicrin

In this case, chloroform (CHCl3) reacts with nitric acid (HNO3) to form chloropicrin (CCl3NO2). The reaction is as follows: \[ CHCl_3 + HNO_3 \longrightarrow CCl_3NO_2 + H_2O \] The reaction is accurate and represents the production of chloropicrin from chloroform and nitric acid. Hence, Option B is correct.

Option C: Formation of Chloretone

In this case, chloroform (CHCl3) reacts with acetone (CH3COCH3) to form Chloretone (CC(C)(O)C(C)(Cl)Cl). The reaction is as follows: \[ CHCl_3 + CH_3COCH_3 \longrightarrow CC(C)(O)C(C)(Cl)Cl \] The reaction is accurate and represents the production of Chloretone from chloroform and acetone. Hence, Option C is correct.

Option D: Dehalogenation of CHCl3

In this case, chloroform (CHCl3) reacts with silver (Ag) to form ethene (CH2=CH2). This reaction is a dehalogenation process, where three chlorine atoms are removed from chloroform. The reaction is as follows: \[ CHCl_3 \stackrel{Ag(\mathrm{s})}{\longrightarrow} CH_2=CH_2 \] However, the given reaction is incorrect. The dehalogenation of chloroform with silver would require the removal of all three chlorine atoms and the addition of three hydrogen atoms to form ethene. This reaction cannot occur using only silver. In fact, this reaction does not proceed directly to give ethene. Instead, reaction of chloroform with silver could produce chloroformate (CHCl2-O-CO-R) or dichlorocarbenes. As a result, Option D is the incorrect option among the given choices.

Key concepts

Chloroform Reactions

Chloroform, also known as trichloromethane, is a common organic solvent and reagent in chemistry. This compound can undergo a variety of chemical reactions due to the presence of the three chlorine atoms attached to the carbon atom. One significant reaction of chloroform is its interaction with nitric acid (HNO₃) to form chloropicrin (CCl₃NO₂).
This reaction occurs because the chloroform acts as a source of trichloromethyl radicals (CCl₃), which combine with the nitro group (from HNO₃) resulting in chloropicrin. Chloropicrin is known for its application as a pesticide and disinfectant due to its powerful fungicidal and insecticidal properties.

• Reaction: CHCl₃ + HNO₃ → CCl₃NO₂ + H₂O

Understanding these reactions helps in not only predicting the products that will form but also designing compounds with desired properties in chemical manufacturing and research.

Dehalogenation

Dehalogenation involves the removal of halogen atoms from an organic molecule, and when it comes to chloroform, it refers to the removal of chlorine atoms. The process usually involves a reduction reaction where the chlorine atoms are replaced by hydrogen atoms, producing a hydrocarbon.
The incorrect reaction involving chloroform: CHCl₃ ightarrow CH₂=CH₂ implies a dehalogenation to produce ethene (ethylene) directly; however, this is not feasible. Theoretical attempts often involve a metal catalyst, like silver (Ag), but this still doesn't result in ethene directly. Typically, intermediate compounds like dichlorocarbenes or complex intermediates form instead.
In practical terms, dehalogenation of aromatic chlorides can be achieved, but for chloroform, careful conditions and specific catalysts are required. Hence, it's essential to understand that removing all chlorine atoms in one step is a complex and rare event, lacking significant feasibility with straightforward laboratory reagents.

Chloropicrin Synthesis

Chloropicrin synthesis is an important chemical process that originates from chloroform and involves its reaction with nitric acid to produce chloropicrin, a compound with significant industrial applications. Chloropicrin itself is a powerful lachrymatory agent, meaning it can cause tears and irritation, which makes it useful as both a pesticide and in tear gas formulations.
The reaction involves the nitration of the trichloromethyl group, where nitric acid introduces a nitro group (NO₂) to form trichloronitromethane. The reaction can be represented as:

• CHCl₃ + HNO₃ → CCl₃NO₂ + H₂O

Industrial synthesis of chloropicrin has to be carefully controlled since both chloroform and nitric acid are hazardous materials on their own. Additionally, chloropicrin's irritating properties require that protective measures are in place during its handling and transport. Understanding this synthesis is vital for chemical safety and application in agricultural chemistry, where chloropicrin plays a central role.