# Oxygen atom reactions with C2H6, C2H4, and C2H2 in ices

## TL;DR

This study investigates how oxygen atoms react with C2 hydrocarbons in ices under cold conditions, revealing pathways to complex organic molecules relevant to interstellar chemistry.

## Contribution

It provides experimental evidence of oxygen atom reactions with C2H6, C2H4, and C2H2 in ices, highlighting their role in forming complex organics at low temperatures.

## Key findings

- Oxygen reacts with hydrocarbons to produce ethanol, acetaldehyde, ethylene oxide, and ketene.
- Branching ratios for product formation are approximately 0.74 for ethanol and 0.47 for ethylene oxide.
- Reactions occur effectively barrierless with O(^1D), enabling chemical complexity in cold ices.

## Abstract

Oxygen atom addition and insertion reactions may provide a pathway to chemical complexity in ices that are too cold for radicals to diffuse and react. We have studied the ice-phase reactions of photo-produced oxygen atoms with C2 hydrocarbons under ISM-like conditions. The main products of oxygen atom reactions with ethane are ethanol and acetaldehyde; with ethylene are ethylene oxide and acetaldehyde; and with acetylene is ketene. The derived branching ratio from ethane to ethanol is ~0.74 and from ethylene to ethylene oxide is ~0.47. For all three hydrocarbons there is evidence of an effectively barrierless reaction with O(^1D) to form oxygen-bearing organic products; in the case of ethylene, there may be an additional barriered contribution of the ground-state O(^3P) atom. Thus, oxygen atom reactions with saturated and unsaturated hydrocarbons are a promising pathway to chemical complexity even at very low temperatures where the diffusion of radical species is thermally inaccessible.