Benzyl chloroformate

Benzyl chloroformate, also known as benzyl chlorocarbonate or Z-chloroformate, is a chemical compound with the formula C8H7ClO2. It is an organic ester formed from benzyl alcohol and phosgene. Benzyl chloroformate is a colorless liquid, although commercial samples can appear yellow. It is used in the synthesis of various organic compounds, serving as a source of the benzyl carbamate protecting group in organic synthesis.

Properties

Benzyl chloroformate has a boiling point of 103 °C at 15 mmHg and a density of 1.213 g/cm³. It is not soluble in water but is readily soluble in organic solvents such as ethanol, diethyl ether, and chloroform. The compound is sensitive to moisture and can hydrolyze, releasing carbon dioxide and forming benzyl alcohol and hydrochloric acid.

Synthesis

Benzyl chloroformate is synthesized through the reaction of benzyl alcohol with phosgene. This process involves the formation of a carbamoyl chloride intermediate, which then reacts with benzyl alcohol to produce benzyl chloroformate and hydrochloric acid. The reaction is typically carried out in an inert solvent under anhydrous conditions to prevent hydrolysis of the product.

Applications

Benzyl chloroformate is primarily used in organic synthesis, particularly in the introduction of the benzyl carbamate (Cbz) protecting group for amines. The Cbz group is widely used to protect primary and secondary amines in peptide synthesis due to its stability under various conditions and its straightforward removal under hydrogenation conditions.

In addition to its role in peptide synthesis, benzyl chloroformate is also used in the synthesis of other organic compounds, including pharmaceuticals and agrochemicals. Its reactivity with amines, alcohols, and other nucleophiles makes it a versatile reagent in organic chemistry.

Safety

Benzyl chloroformate is a highly reactive compound and should be handled with caution. It is corrosive and can cause severe burns upon contact with skin or eyes. Inhalation of its vapors can lead to respiratory irritation. Appropriate personal protective equipment, including gloves, goggles, and a fume hood, should be used when handling this chemical.

Environmental Impact

There is limited information on the environmental impact of benzyl chloroformate. However, due to its reactivity and potential to hydrolyze, it should be disposed of properly to minimize any potential environmental hazards.

See Also

• Protecting group
• Peptide synthesis
• Benzyl alcohol
• Phosgene