Chlorinated paraffins (CPs) can be mixtures of nearly a half-million possible isomers. Despite the extensive use of CPs, their isomer composition and effects on the environment remain poorly understood. Here, we reveal the isomeric distributions of nine CP mixtures with single-chain lengths (C_14/15) and varying degrees of chlorination. The molar distribution of C_nH_2n+2–mCl_m in each mixture was determined using high-resolution mass spectrometry (MS). Next, the mixtures were analyzed by applying both one-dimensional ¹H, ¹³C and two-dimensional nuclear magnetic resonance (NMR) spectroscopy. Due to substantially overlapping signals in the experimental NMR spectra, direct assignment of individual isomers was not possible. As such, a new NMR spectral matching approach that used massive NMR databases predicted by a neural network algorithm to provide the top 100 most likely structural matches was developed. The top 100 isomers appear to be an adequate representation of the overall mixture. Their modeled physicochemical and toxicity parameters agree with previous experimental results. Chlorines are not evenly distributed in any of the CP mixtures and show a general preference at the third carbon. The approach described here can play a key role in understanding of complex isomeric mixtures such as CPs that cannot be resolved by MS alone.

中文翻译：

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氯化石蜡中的氯并非均匀替代：复杂污染物混合物中异构鉴别的预测NMR模式匹配框架。

氯化石蜡（CPs）可能是将近50万种异构体的混合物。尽管CP的广泛使用，但它们的异构体组成及其对环境的影响仍然知之甚少。在这里，我们揭示了具有单链长度（C _14/15）和不同氯化度的9种CP混合物的同分异构分布。使用高分辨率质谱（MS）确定每种混合物中C _n H _{2 n + 2 –m} Cl _m的摩尔分布。接下来，通过同时应用一维¹ H，¹³分析混合物C和二维核磁共振（NMR）光谱。由于实验NMR光谱中的信号基本重叠，因此无法直接分配单个异构体。因此，开发了一种新的NMR光谱匹配方法，该方法使用了由神经网络算法预测的大规模NMR数据库来提供前100个最可能的结构匹配。前100个异构体似乎足以代表整个混合物。他们建模的理化和毒性参数与以前的实验结果一致。氯气在任何CP混合物中均分布不均，并且在第三个碳原子上表现出普遍的偏爱。此处描述的方法在理解复杂的异构体混合物（例如CP不能单独由MS分离）中起关键作用。