Question

Mustard gas, Cl–CH2CH2–S–CH2CH2–Cl, was used as a poisonous chemical agent in World War I. Mustard gas is much more toxic than a typical primary alkyl chloride. Its toxicity stems from its ability to alkylate amino groups on important metabolic enzymes, rendering the enzymes inactive.a. Propose a mechanism to explain why mustard gas is an exceptionally potent alkylating agent.b. Bleach (sodium hypochlorite, NaOCl, a strong oxidizing agent) neutralizes and inactivates mustard gas. Bleach is also effective on organic stains because it oxidizes colored compounds to colorless compounds. Propose products that might be formed by the reaction of mustard gas with bleach.

Accepted Answer

Step 1: Analyze the structure of mustard gas (Cl-CH₂CH₂-S-CH₂CH₂-Cl). Note that it contains two alkyl chloride groups and a sulfur atom in the center, which can act as a nucleophile. The sulfur atom's lone pair can initiate an intramolecular reaction, forming a three-membered episulfonium ion intermediate. Step 2: Propose the mechanism for mustard gas's alkylating ability. The sulfur atom attacks one of the carbon atoms bonded to a chlorine atom, displacing the chloride ion and forming the episulfonium ion. This intermediate is highly reactive and can easily react with nucleophiles, such as amino groups on enzymes, leading to alkylation and enzyme inactivation. Step 3: Consider the reaction of mustard gas with bleach (NaOCl). Bleach is a strong oxidizing agent and can oxidize the sulfur atom in mustard gas. This oxidation likely converts the sulfur atom into a sulfoxide (R-S(=O)-R') or sulfone (R-S(=O)₂-R'), which are less reactive and no longer capable of forming the episulfonium ion. Step 4: Propose the products of the reaction between mustard gas and bleach. The oxidation of the sulfur atom disrupts the ability of mustard gas to form the episulfonium ion, rendering it non-toxic. The products might include oxidized sulfur compounds such as sulfoxides or sulfones, along with chloride ions (Cl⁻) released during the reaction. Step 5: Summarize the neutralization process. The reaction with bleach effectively inactivates mustard gas by oxidizing the sulfur atom, preventing the formation of the reactive episulfonium ion. This mechanism explains why bleach is effective in neutralizing mustard gas and highlights its utility as a decontaminant.

비슷한 문제에 대한 검증된 영상 답변:

주요 개념

Alkylation Mechanism

Oxidizing Agents

Chemical Reactivity of Mustard Gas