Elucidating the Reaction Mechanisms between Triazine and Hydrogen Sulfide with pH Variation Using Mass Spectrometry
Elucidating the Reaction Mechanisms between Triazine and Hydrogen Sulfide with pH Variation Using Mass Spectrometry
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使用质谱法阐明三嗪和硫化氢之间随 pH 变化的反应机制
DOI：
10.1021/acs.analchem.8b03107
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发表时间：
2018
影响因子：
7.4
通讯作者：
Zhang Zhiping
中科院分区：
文献类型：
--
作者：
Wang Xiaoting;Zheng Yajun;Shi Jun;Gong Xiaoyun;Ji Yue;Han Weiwei;Jiang You;Austin Daniel E.;Fang Xiang;Zhang Zhiping
三嗪是最经济、最有效的脱除硫化氢的清除剂之一，但三嗪与硫化氢在溶液中随pH变化的反应机理尚不清楚。在这里，我们表明，反应过程可以直接用纸喷雾质谱仪来探测，其中，由于氢键作用，非质子溶剂(如乙腈)比质子溶剂(如甲醇)更有利于观察反应中间产物。改变反应的pH值会导致完全不同的反应路径。在pH为5.58~7.73的范围内，主要产物为噻二嗪。在pH值为3.02-3.69的条件下，噻二嗪被转化为2-(5-(2-hydroxyethyl)-1，3，5-thiadiazinan-3-yl)acetaldehyde，，这与传统的类似反应途径不同。然而，当在反应中加入氨，并将pH调节到8.45-9.43的范围内，三嗪很容易发生水解，生成的中间体与三嗪原位生成的氨和甲醛反应生成1-(2-hydroxyethyl)-3，5，7-triaza-1-azoniatricyclo[3.3.1.13，7]癸烷(HTAD)。进一步提高pH至10.27-11.21会导致HTAD的分解。在实验观察的基础上，结合高分辨和串联质谱学的证据，提出了三嗪与硫化氢反应的可能机理，以及三嗪在不同pH条件下的衍生反应。
Triazine is one of the most economical and effective scavengers for hydrogen sulfide (H2S) removal, but the reaction mechanisms between triazine and H2S with pH variation in solution are still poorly understood. Herein, we show that the reaction process can be directly probed by means of paper spray mass spectrometry, in which an aprotic solvent (e.g., acetonitrile) is more favorable to the observation of reaction intermediates than a protic solvent (e.g., methanol), because of hydrogen bond interaction. Varying the pH of the reaction leads to completely different reaction pathways. With the pH in the range of 5.58 to 7.73, the major product was thiadiazine. With a pH of 3.02–3.69, thiadiazine is converted to 2-(5-(2-hydroxyethyl)-1,3,5-thiadiazinan-3-yl)acetaldehyde, which differs from the traditional pathway of analogous reactions. However, as ammonia was added into the reaction and the pH was adjusted to the range 8.45–9.43, triazine readily undergoes hydrolysis, and the formed intermediate reacts with ammonia and formaldehyde generated in situ from triazine to produce 1-(2-hydroxyethyl)-3,5,7-triaza-1-azoniatricyclo [3.3.1.13,7]decane (HTAD). Further increasing the pH up to 10.27–11.21 leads to the decomposition of HTAD. Based on the experimental observation and evidence from high-resolution and tandem mass spectrometry, we propose the plausible reaction mechanisms between triazine and H2S, as well as the derived reaction from triazine under different pH conditions.