Max-Planck-Institut für Radioastronomie (MPIfR), Auf dem Hügel 69, 53121 Bonn, Germany.
Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853-6801, USA.
Science. 2014 Sep 26;345(6204):1584-7. doi: 10.1126/science.1256678.
The largest noncyclic 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 nonterminal 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.
在星际介质（ISM）中检测到的最大的非循环分子是具有直链碳骨架的有机分子。我们报告了支链烷基分子异丙基氰（i-C3H7CN）在星际空间中的首次检测，其丰度是其直链结构异构体的 0.4 倍。这一发现表明，支链碳链分子可能在 ISM 中普遍存在。我们的天体化学模型表明，两种异构体都是通过分子自由基的加成，在尘埃颗粒冰壳内或之上生成的，尽管反应途径不同。异丙基氰的生成似乎需要在链中的非末端碳原子上添加一个官能团。因此，它的检测预示着在 ISM 中存在氨基酸，因为这种侧链结构是氨基酸的一个关键特征。
