次磺酸

在化学中，次磺酸是一种含氧的有机化合物的官能基，其通式为RSOH，其中R≠H（若R=H则为硫氧化氢）。次磺酸是一种有机硫含氧酸的第一个成员，其他还包括了亚磺酸（RSO₂H）、磺酸（RSO₃H）等。

性质

与亚磺酸和磺酸相比，简单的次磺酸（如：甲次磺酸，CH₃SOH）具有高度活性，极容易发生化学反应，因此难以从溶液中进行分离。气态的甲次磺酸半衰期约为1分钟。借由观测甲次磺酸的微波光谱（转动光谱）发现他的结构为 CH₃–S–O–H^[1]。次磺酸通过空间位阻的影响，可以稳定存在，防止次磺酸凝结形成硫代亚磺酸酯（RS(O)SR），如大蒜中的大蒜素。通过使用X-射线结晶学的分析，这种稳定的次磺酸酸的结构被证实是R-S-O-H键^[2]^[3]。因空间位阻而稳定的次磺酸，如1-三蝶烯次磺酸（1-triptycenesulfenic acid）已测得其pK_a为12.5，且O-H键的解离能（BDE）为 71.9 ± 0.3 kcal/mol，可与有机过氧化物的pKa ≥14和O–H BDE ∼88 kcal/mol做比较^[4]。

参见

参考文献

^ Penn RE, Block E, Revelle LK. Methanesulfenic Acid. Journal of the American Chemical Society. 1978, 100 (11): 3622–3624. doi:10.1021/ja00479a068.
^ Goto K, Holler M, Okazaki R. Synthesis, Structure, and Reactions of a Sulfenic Acid Bearing a Novel Bowl-Type Substituent: The First Synthesis of a Stable Sulfenic Acid by Direct Oxidation of a Thiol. Journal of the American Chemical Society. 1997, 119 (6): 1460–1461. doi:10.1021/ja962994s.
^ Ishii A, Komiya K, Nakayama J. Synthesis of a Stable Sulfenic Acid by Oxidation of a Sterically Hindered Thiol (Thiophenetriptycene-8-thiol)1 and Its Characterization. Journal of the American Chemical Society. 1996, 118 (50): 12836–12837. doi:10.1021/ja962995k.
^ McGrath AJ, Garrett GE, Valgimigli L, Pratt DA. The redox chemistry of sulfenic acids. Journal of the American Chemical Society. 2010, 132 (47): 16759–16761. doi:10.1021/ja1083046.

[1] Penn RE, Block E, Revelle LK. Methanesulfenic Acid. Journal of the American Chemical Society. 1978, 100 (11): 3622–3624. doi:10.1021/ja00479a068.

[2] Goto K, Holler M, Okazaki R. Synthesis, Structure, and Reactions of a Sulfenic Acid Bearing a Novel Bowl-Type Substituent: The First Synthesis of a Stable Sulfenic Acid by Direct Oxidation of a Thiol. Journal of the American Chemical Society. 1997, 119 (6): 1460–1461. doi:10.1021/ja962994s.

[3] Ishii A, Komiya K, Nakayama J. Synthesis of a Stable Sulfenic Acid by Oxidation of a Sterically Hindered Thiol (Thiophenetriptycene-8-thiol)1 and Its Characterization. Journal of the American Chemical Society. 1996, 118 (50): 12836–12837. doi:10.1021/ja962995k.

[4] McGrath AJ, Garrett GE, Valgimigli L, Pratt DA. The redox chemistry of sulfenic acids. Journal of the American Chemical Society. 2010, 132 (47): 16759–16761. doi:10.1021/ja1083046.

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