定义Definition
溴化氢 HBr 是无色、有刺激性的气体，极易溶于水形成氢溴酸，是强酸。它比 HCl 更易被氧化，因此不能用浓硫酸与溴化钠制得纯净的 HBr。在有机化学中，HBr 与烯烃加成生成溴代烃。
Hydrogen bromide, HBr, is a colourless, choking gas that dissolves readily in water to give hydrobromic acid, a strong acid. It is more easily oxidised than HCl, so pure HBr cannot be made from sodium bromide and concentrated sulfuric acid. In organic chemistry it adds to alkenes to give bromoalkanes.
与浓硫酸的反应Reaction with concentrated sulfuric acid
NaBr + H₂SO₄ → NaHSO₄ + HBr，但部分 HBr 被浓硫酸氧化：2HBr + H₂SO₄ → Br₂ + SO₂ + 2H₂O，可见红棕色溴蒸气。改用不具氧化性的浓磷酸可得纯净的 HBr。
NaBr + H₂SO₄ → NaHSO₄ + HBr, but some HBr is oxidised by the acid: 2HBr + H₂SO₄ → Br₂ + SO₂ + 2H₂O, and red-brown bromine vapour appears. Concentrated phosphoric acid, which is not oxidising, gives pure HBr.
与烯烃加成Addition to alkenes
与丙烯加成按马氏规则主要生成 2-溴丙烷；在过氧化物存在下按自由基机理进行，主要生成 1-溴丙烷（反马氏加成，过氧化物效应）。
With propene, addition follows Markovnikov's rule to give mainly 2-bromopropane; with peroxides present it goes by a radical mechanism to give mainly 1-bromopropane (anti-Markovnikov addition, the peroxide effect).
化学性质Chemical properties
被浓硫酸氧化：2HBr + H₂SO₄ → Br₂ + SO₂ + 2H₂O
Oxidised by concentrated sulfuric acid: 2HBr + H₂SO₄ → Br₂ + SO₂ + 2H₂O
年表Timeline
- 1933
卡拉施报道过氧化物使 HBr 发生反马氏加成
Kharasch reports the peroxide effect giving anti-Markovnikov addition of HBr