Organic chemistry can be represented as a network of reactions and studied by mathematical tools of graph theory. In this paper, the structure of a network of organic reactions has been studied using several graph theory metrics. The network was based on a section of chemical space downloaded from Reaxys. The studied area of chemistry corresponds to the chemistry of terpenes and includes 12 238 931 species and 12 939 422 reactions after filtering of an initial set of 35 million reactions. The analysis of the network statistics confirmed that the network was scale-free, as was reported in the earlier literature from the analysis of a much smaller network. Many networks in other technological or non-technological areas show that nodes have a preference as to whether they connect to highly connected or scarcely connected nodes, but for chemistry no such trend was observed. It was found that the network of reactions exhibits “small world” behaviour and in simile to the ‘six degrees of separation’ encountered in social networks, on average, any molecule could be made from any other molecule in six synthesis steps. Scale-free networks have hubs in their wiring pattern. By investigating whether these hubs are not only well studied but also frequently used, it was found that they concentrated a large share of the network's load onto themselves, showing that the network's structure impacts the usage of chemistry, or vice versa, implying a hierarchy of molecules.

中文翻译：

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有机化学网络的统计数据†

有机化学可以表示为一个反应网络，可以通过图论的数学工具进行研究。在本文中，已经使用几种图论度量研究了有机反应网络的结构。该网络基于从Reaxys下载的一部分化学空间。所研究的化学领域与萜烯的化学性质相对应，在过滤掉最初的3500万个反应集后，包括12 238 931种和12 939 422个反应。对网络统计数据的分析证实了该网络是无标度的，正如早期文献中从对一个小得多的网络的分析中所报道的那样。其他技术或非技术领域的许多网络表明，节点对于连接到高度连接还是很少连接的节点具有优先权，但是在化学上没有观察到这种趋势。发现反应网络表现出“小世界”行为，并且与社交网络中遇到的“六个分离度”相似，平均而言，任何分子都可以在六个合成步骤中由任何其他分子制成。无标度网络在其布线模式中具有集线器。通过调查这些集线器是否不仅得到了很好的研究，而且还经常使用，发现它们将网络负载的很大一部分集中在自己身上，表明网络的结构会影响化学物质的使用，或者 任何分子都可以在六个合成步骤中由任何其他分子制成。无标度网络在其布线模式中具有集线器。通过调查这些集线器是否不仅得到了很好的研究，而且还经常使用，发现它们将网络负载的很大一部分集中在自己身上，表明网络的结构会影响化学物质的使用，或者 任何分子都可以在六个合成步骤中由任何其他分子制成。无标度网络在其布线模式中具有集线器。通过调查这些集线器是否不仅得到了很好的研究，而且还经常使用，发现它们将网络负载的很大一部分集中在自己身上，表明网络的结构会影响化学物质的使用，或者反之亦然，这意味着分子的层次结构。