Gas-phase sugar formation using hydroxymethylene as the reactive formaldehyde isomer

Area of Science:

• Astrochemistry
• Organic Chemistry
• Biochemistry

Background:

• Carbohydrates (CH2O)n are carbon compounds formally derived from water.
• Hydroxymethylene (H-C̈-OH), a reactive species and isomer of formaldehyde, is proposed as a sugar building block.
• The detection and reactivity of hydroxymethylene have been challenging until recently.

Purpose of the Study:

• To investigate the reaction between formaldehyde and hydroxymethylene.
• To explore the potential of this reaction for prebiotic sugar synthesis under extraterrestrial conditions.
• To link this reaction pathway to known sugar formation mechanisms like the formose reaction.

Main Methods:

• Studied the reaction between formaldehyde and its isomer, hydroxymethylene.
• Investigated the reaction mechanism, identifying it as a carbonyl-ene-type transformation.
• Conducted experiments at cryogenic temperatures in the absence of base and solvent.

Main Results:

• Demonstrated a nearly barrierless reaction between formaldehyde and hydroxymethylene, forming glycolaldehyde.
• Showed that hydroxymethylene can serve as a building block for iterative sugar synthesis, producing glyceraldehyde.
• Observed that the thermodynamically favored dihydroxyacetone and further branched sugars do not form under these conditions.

Conclusions:

• The reaction provides a plausible pathway for sugar formation in non-aqueous extraterrestrial environments.
• This study links the formose (Butlerow) reaction to sugar synthesis under conditions relevant to interstellar clouds.
• The findings highlight the role of simple molecules like formaldehyde and hydroxymethylene in prebiotic chemistry.