Singlet Halophenylcarbenes as Strong Hydrogen-Bond Acceptors.

Area of Science:

• Photochemistry
• Matrix Isolation Spectroscopy
• Carbene Chemistry

Background:

• Carbenes are highly reactive intermediates.
• Understanding carbene reactions in condensed phases is crucial for astrochemistry and synthetic chemistry.
• Previous studies have explored carbene reactions in various environments.

Purpose of the Study:

• To investigate the photochemical reactions of chlorophenylcarbene and fluorophenylcarbene with water.
• To characterize the reaction products formed in water-doped argon matrices and amorphous water ice.
• To determine the stability of primary insertion products and identify reaction pathways.

Main Methods:

• Generation of chlorophenylcarbene and fluorophenylcarbene via photolysis of diazirines in argon matrices at cryogenic temperatures.
• Induction of water diffusion and formation of hydrogen-bonded carbene-water complexes by annealing.
• UV photolysis of these complexes and diazirines in amorphous water ice.
• Spectroscopic analysis to identify reaction products.

Main Results:

• UV photolysis of carbene-water complexes yielded benzaldehyde and hydrogen halides.
• Similar products were observed upon photolysis of diazirines in amorphous water ice.
• The primary carbene insertion product into the O-H bond of water proved unstable under these conditions, leading to secondary photolysis.
• A stable primary photochemical insertion product was observed in the reaction of chlorophenylcarbene with methanol.

Conclusions:

• Benzaldehyde is a secondary photolysis product in the reaction of phenylcarbenes with water under the studied conditions.
• The reaction pathway involves an unstable primary insertion intermediate.
• Methanol serves as a suitable solvent for observing stable primary carbene insertion products into O-H bonds.