Abstract n-Alkan-2-ones (methyl ketones) ranging from C14 to C31, were recovered from the polar fraction of an extract of a torbanite from the Sydney Basin, Australia. There was a very slight even-over-odd predominance between C20 and C24 n-alkan-2-ones, together with remarkably high contents of the C24, C26 and C28 homologues. A range of C16 to C28 macrocyclic alkanes, as well as their corresponding methylated counterparts (C19–C24), was also detected in the saturate fraction obtained after molecular sieve treatments. Due to the relatively high contents of the n-alkan-2-ones and macrocyclic alkanes, we were able to carry out GC–irMS analysis to determine the δ13C values of specific compounds. The even-numbered n-alkan-2-ones from C24 to C28 were significantly 13C-enriched, compared to the other n-alkan-2-ones, which had similar isotopic values to the macrocyclic alkanes. The majority of the n-alkan-2-ones detected here probably had the same algal source as the macrocyclic alkanes, which is likely to be lipids and algaenan of the green microalga Botryococcus braunii. However, the distribution and 13C enrichment of C24, C26 and C28 n-alkan-2-ones indicates that an additional source must be present.

中文翻译：

---

同位素富集的 n-alkan-2-ones 在澳大利亚悉尼盆地的一种山梨石中具有均匀的链优势

摘要 从澳大利亚悉尼盆地的山梨石提取物的极性部分回收了 C14 到 C31 范围内的 n-Alkan-2-ones（甲基酮）。C20 和 C24 n-alkan-2-ones 之间存在非常轻微的偶数-奇数优势，以及 C24、C26 和 C28 同系物的含量非常高。在分子筛处理后获得的饱和馏分中也检测到一系列 C16 至 C28 大环烷烃，以及它们相应的甲基化对应物（C19-C24）。由于 n-alkan-2-ones 和大环烷烃的含量相对较高，我们能够进行 GC-irMS 分析以确定特定化合物的 δ13C 值。与其他 n-alkan-2-one 相比，从 C24 到 C28 的偶数 n-alkan-2-one 显着富含 13C，与大环烷烃具有相似的同位素值。这里检测到的大多数 n-alkan-2-ones 可能与大环烷烃具有相同的藻类来源，这很可能是绿色微藻 Botryococcus braunii 的脂质和海藻素。然而，C24、C26 和 C28 n-alkan-2-ones 的分布和 13C 富集表明必须存在额外的来源。