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溴化氢

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溴化氢
IUPAC名
Hydrogen Bromide
识别
CAS号 10035-10-6  ✓
PubChem 260
ChemSpider 255
SMILES
Beilstein 3587158
UN编号 1048
EINECS 233-113-0
ChEBI 47266
RTECS MW3850000
KEGG C13645
MeSH Hydrobromic+Acid
性质
化学式 HBr
摩尔质量 80.912 g·mol⁻¹
外观 无色气体
密度 3.307 g/L (气)
熔点 –86.80°C (186.35 K)
沸点 –66.38°C (206.77 K)
溶解性 193 g/100 ml (20 °C)
pKa ≈ –9
结构
分子构型 直线形
偶极矩 0.82 D
危险性
MSDS 氢溴酸 溴化氢
主要危害 有毒,腐蚀性
NFPA 704
NFPA 704.svg
2
3
1
COR
若非注明,所有数据均出自一般条件(25 ℃,100 kPa)下。

溴化氢化学式HBr二元化合物,标准情况下为气体。溴化氢溶于水得到氢溴酸,氢溴酸中加入脱水剂也可得到溴化氢。

性质

标准情况下,溴化氢是不可燃气体,带有酸味,在潮湿空气中发烟。溴化氢可溶于水生成氢溴酸,室温下饱和溶液的浓度为68.85%(质量比),恒沸混合物中含47.38%质量的溴化氢,恒沸混合物沸点126°C。氢溴酸几乎完全离解为H+和Br

用途

HBr在化学合成中有很多应用。例如,可由它与反应来制取溴代烃

ROH + HBr → R+OH2 + Br → RBr + H2O

HBr与烯烃加成得到溴代烃:

RCH=CH2 + HBr → RCH(Br)–CH3

如在过氧化物的存在下进行此反应,则不遵循马氏规则。

HBr与炔烃加成得到溴代烯烃,产物为反式:

RC≡CH + HBr → RCH(Br)=CH2

继续反应得到偕二溴代烷,遵循马氏规则

RC(Br)=CH2 + HBr → RC(Br2)–CH3

此外,HBr也可用于环氧化合物内酯的开环合成溴缩醛,以及很多有机反应的催化剂。[1][2][3][4]

工业制取

氯化氢盐酸不同的是,工业上,溴化氢与氢溴酸并非大量需求的化学品,并且是通过200-400°C和石棉催化下,氢气反应制取的。[2][5]

实验室制备

实验室中可通过很多方法制备HBr。一种是用硫酸NaBr反应:[6]

NaBr(s) + H2SO4(aq) → NaHSO4(s) + HBr(g)

但该法产率不高,生成的HBr会被硫酸氧化为溴:

2HBr(g) + H2SO4(aq) → Br2(g) + SO2(g) + 2H2O(l)

因此常选用非氧化性酸,如磷酸乙酸作为反应物。

或者可以通过四氢化萘的溴化来制备:[6]

C10H12 + 4Br2 → C10H8Br4 + 4HBr(g)

亦用苯酚与浓水反应制取:

C6H5OH+3Br2→C6H2Br3OH(三溴苯酚)+3HBr

干燥的HBr气体可以方便的由有机羧酸同LiBr在高温条件(>150 oC)下反应得到[7],然后通过氮气流将HBr带出。

但需要注意的是,LiBr极易吸水,需要使用无水LiBr。如

PhCOOH + LiBr → PhCOOLi + HBr↑

纯净氢气与溴在铂催化下反应:[6]

Br2 + H2 → 2HBr(g)

亚磷酸还原溴:[2]

Br2 + H3PO3 + H2O → H3PO4(s) + 2HBr(g)

少量无水溴化氢还可由溴化三苯基𬭸在二甲苯中回流分解制得。[1]

以上方法得到的HBr常含有Br2杂质,可通过使其与Cu或苯酚反应除去。[5]

参考资料

  1. ^ 1.0 1.1 Hercouet, A.;LeCorre, M. (1988) Triphenylphosphonium bromide: A convenient and quantitative source of gaseous hydrogen bromide. Synthesis, 157-158.
  2. ^ 2.0 2.1 2.2 Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements; Butterworth-Heineman: Oxford, Great Britain; 1997; pp. 809-812.
  3. ^ Carlin, William W. U.S. Patent 4,147,601页面存档备份,存于互联网档案馆), April 3, 1979
  4. ^ Vollhardt, K. P. C.; Schore, N. E. Organic Chemistry: Structure and Function; 4th Ed.; W. H. Freeman and Company: New York, NY; 2003.
  5. ^ 5.0 5.1 Ruhoff, J. R.; Burnett, R. E.; Reid, E. E. "Hydrogen Bromide (Anhydrous)" Organic Syntheses, Vol. 15, p.35 (Coll. Vol. 2, p.338).
  6. ^ 6.0 6.1 6.2 WebElements: Hydrogen Bromide. [2008-05-06]. (原始内容存档于2008-05-13). 
  7. ^ Suzuki, S, Francisco, S. California Research Corporation, US 3199953, 1965.
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溴化氢
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