Detection of a branched alkyl molecule in the interstellar medium: iso-propyl cyanide

TL;DR

This paper reports the first detection of a branched alkyl molecule, iso-propyl cyanide, in the interstellar medium, indicating that complex branched molecules are likely common in space and may be precursors to amino acids.

Contribution

It is the first interstellar detection of a branched alkyl molecule, expanding understanding of molecular complexity in space and suggesting pathways for amino acid formation.

Findings

Detection of iso-propyl cyanide in the ISM.

Branched molecules are as abundant as straight-chain isomers.

Different formation pathways for branched and straight-chain molecules.

Abstract

The largest non-cyclic molecules detected in the interstellar medium (ISM) are organic with a straight-chain carbon backbone. We report an interstellar detection of a branched alkyl molecule, iso-propyl cyanide (i-C3H7CN), with an abundance 0.4 times that of its straight-chain structural isomer. This detection suggests that branched carbon-chain molecules may be generally abundant in the ISM. Our astrochemical model indicates that both isomers are produced within or upon dust grain ice mantles through the addition of molecular radicals, albeit via differing reaction pathways. The production of iso-propyl cyanide appears to require the addition of a functional group to a non-terminal carbon in the chain. Its detection therefore bodes well for the presence in the ISM of amino acids, for which such side-chain structure is a key characteristic.