Autoxidation Reaction Mechanism for l-Ascorbic Acid in Methanol without Metal Ion Catalysis

Area of Science:

• Biochemistry
• Organic Chemistry

Background:

• Ascorbic acid (ASA) autoxidation is crucial in biological systems and food chemistry.
• Previous research primarily focused on the dehydro-l-ascorbic acid (DASA) pathway.

Purpose of the Study:

• To investigate the autoxidation of ascorbic acid (ASA) in methanol without metal catalysts.
• To identify novel initial autoxidation products and elucidate the reaction mechanism.

Main Methods:

• Studied the autoxidation of ASA in methanol.
• Identified reaction products using analytical techniques.
• Varied reaction conditions to determine product yields.

Main Results:

• Identified methyl l-threonate and threonic acid as initial autoxidation products via C(2)-C(3) fission.
• This pathway bypasses the previously accepted DASA route.
• Mono-dissociated ASA showed higher reactivity than non-dissociated ASA.

Conclusions:

• A new C(2)-C(3) fission pathway for ASA autoxidation exists, distinct from the DASA route.
• Solvent polarity and ASA dissociation state influence the reaction products.
• Understanding these pathways is vital for controlling ASA degradation.