Question

How is the following conversion carried out $:$ Chloroform into diethyl carbonate $?$

Answer 1

Hint: Chloroform , $CH{I_3}$ , is an organic compound with IUPAC name trichloromethane. It is a colourless, dense liquid with a pleasant smell. It is non flammable and used as solvent in various industries. Chloroform was widely used for anaesthesia during operations. Oxidation of chloroform yields diethyl carbonate.

Complete answer: Chloroform is converted to diethyl carbonate in two steps:
(i)Chloroform when exposed to sunlight or air undergoes oxidation easily to form a highly toxic gas, phosgene $(COC{l_2})$ along with hydrochloric acid. The reaction is as given below:
$CHC{l_3}\, + \,\dfrac{1}{2}{O_2}\,\,\xrightarrow{{hv\,\,\,or\,\,air}}\,COC{l_2}\, + \,HCl$$CHC{l_3}\, + \,\dfrac{1}{2}{O_2}\,\,\xrightarrow{{hv\,\,\,or\,\,air}}\,COC{l_2}\, + \,HCl$

(ii)Ethyl alcohol is made to react with phosgene to yield a less harmful product i.e., diethyl carbonate, ${(O{C_2}{H_5})_2}C{O_{}}$.
$COC{l_2}\, + \,2{C_2}{H_5}OH\,\, \to \,\,{(O{C_2}{H_5})_2}CO\, + \,\,2HCl$
Diethyl carbonate is an ester of carbonic acid and ethanol. It is a clear liquid at room temperature. We know that chloroform gets oxidised to extremely poisonous phosgene on exposure to sunlight and air. Therefore, it is always stored in closed dark colored bottles away from sunlight. Ethanol is added to these bottles in order to prevent oxidation. And as a result diethyl carbonate is formed. Here, ethanol acts as an inhibitor.

Note:
Chloroform was a widely accepted anaesthetic earlier. But breathing it even for a short while can cause fatigue, headache and dizziness. Long-time exposure to chloroform can damage liver and kidneys. In addition to that, exposure to sunlight and air causes oxidation and results in the formation of highly toxic and harmful phosgene. Due to the difficulty in handling and the medical illnesses it can cause, nowadays chloroform is replaced by halothane $(C{F_3}CHClBr)$ which is relatively safe.