Dimethoxymethane-hydrogen chloride interaction: gas phase versus low-temperature behavior studied using matrix...

Area of Science:

• Chemical kinetics and reaction mechanisms.
• Matrix isolation spectroscopy.
• Computational chemistry.

Background:

• Dimethoxy methane (DMM) and hydrogen chloride (HCl) can undergo reactions in the gas phase.
• Understanding reaction intermediates and pathways is crucial in chemical synthesis.

Purpose of the Study:

• To investigate the reaction pathway of DMM and HCl under different conditions.
• To characterize the intermediate formed during the reaction.
• To explore the influence of matrix isolation on the reaction outcome.

Main Methods:

• Gas-phase reaction studies with Ar/N2 mixtures.
• Low-temperature matrix isolation of DMM and HCl.
• Infrared spectroscopy to detect vibrational frequency shifts.
• Density Functional Theory (DFT) calculations (B3LYP/6-311++G**) for structural and energetic analysis.

Main Results:

• Gas-phase premixing of DMM and HCl produced cis-chloromethyl methyl ether (cis-CMME) and methanol via nucleophilic substitution.
• Codeposition of DMM and HCl in an Ar matrix resulted in a hydrogen-bonded alkoxy adduct, identified by vibrational frequency shifts.
• Computational analysis revealed a single minimum for the DMM-HCl adduct.
• The nucleophilic substitution reaction was suppressed in the low-temperature matrix.

Conclusions:

• Matrix isolation prevents the gas-phase nucleophilic substitution reaction between DMM and HCl, likely due to the cage effect.
• The hydrogen-bonded alkoxy adduct is a probable intermediate in the gas-phase reaction.
• Spectroscopic and computational methods provide insights into reaction mechanisms and intermediates.