A cis-diol, or vicinal diol, is a compound bearing two hydroxyl groups (–OH) on adjacent carbons and on the same face of the molecule. It is formed by the gentle, syn oxidation of an alkene, for example with osmium tetroxide (OsO₄). It matters because this reaction adds two –OH groups stereospecifically to the same side of the former double bond, in contrast to the anti dihydroxylation that proceeds via an epoxide.

顺式二醇(邻二醇)是在相邻碳上、且位于分子同一面带有两个羟基(–OH)的化合物。它由烯烃经温和的顺式氧化生成,例如用四氧化锇(OsO₄)。它之所以重要,是因为该反应立体专一地把两个 –OH 加到原双键的同一侧,与经由环氧化物进行的反式双羟基化形成对照。