定义Definition
臭氧化反应是臭氧与烯烃(或炔烃)反应切断碳–碳双键,经臭氧化物中间体后,经还原处理得到醛、酮,或经氧化处理得到羧酸、酮的反应。
Ozonolysis cleaves C=C (or C≡C) bonds with ozone; through an ozonide intermediate, reductive work-up gives aldehydes and ketones and oxidative work-up gives carboxylic acids and ketones.
机理Mechanism
克里吉机理:臭氧与双键 1,3-偶极环加成生成初级臭氧化物(1,2,3-三氧杂环戊烷),它断裂为羰基化合物与羰基氧化物(克里吉中间体),二者再重新 1,3-偶极环加成生成次级臭氧化物(1,2,4-三氧杂环戊烷)。
Criegee mechanism: 1,3-dipolar cycloaddition gives the primary ozonide (1,2,3-trioxolane), which splits into a carbonyl and a carbonyl oxide (Criegee intermediate); these recombine to the secondary ozonide (1,2,4-trioxolane).
后处理Work-up
还原性(Me₂S、Zn/AcOH、PPh₃)→ 醛和酮;氧化性(H₂O₂)→ 羧酸和酮;NaBH₄ → 醇。−78 °C 溶液出现蓝色表示臭氧过量、反应完成。臭氧化物易爆,不宜分离。
Reductive (Me₂S, Zn/AcOH, PPh₃) → aldehydes and ketones; oxidative (H₂O₂) → acids and ketones; NaBH₄ → alcohols. A blue colour at −78 °C signals excess ozone. Ozonides are explosive and are not isolated.
由来与用途Origin and uses
舍恩拜因于 1840 年发现臭氧;卡尔·哈里斯(1903 年起)把臭氧化系统用于测定天然橡胶、萜类中双键位置。现代用于合成及工业制壬二酸(由油酸)。大气中臭氧对烯烃的氧化也是城市光化学烟雾与二次气溶胶的来源之一。
Schönbein discovered ozone in 1840; from 1903 Carl Harries used ozonolysis to locate double bonds in rubber and terpenes. Today it serves synthesis and industry (azelaic acid from oleic acid). Atmospheric ozonolysis of alkenes contributes to smog and secondary aerosol.
反应Reactions
CH₂Cl₂ 或 MeOH,−78 °C 通入 O₃;加 Me₂S 或 Zn/AcOH 还原
O₃ bubbled through CH₂Cl₂ or MeOH at −78 °C, then Me₂S or Zn/AcOH
1,3-偶极环加成生成初级臭氧化物。
1,3-Dipolar cycloaddition to the primary ozonide.
逆环加成生成羰基与克里吉中间体。
Retro-cycloaddition to a carbonyl and Criegee intermediate.
重组为次级臭氧化物,再还原或氧化分解。
Recombination to the secondary ozonide, then reductive or oxidative cleavage.
环烯开环得二醛。
Ring opening to a dialdehyde.
反应机理图Mechanism
红色弯箭头表示一对电子的移动方向:从电子来源(孤对电子或化学键)指向电子去向。Red curly arrows show where an electron pair moves: from its source (lone pair or bond) to its destination.
臭氧与双键 1,3-偶极环加成
1,3-Dipolar cycloaddition of ozone to the alkene
初级臭氧化物(分子臭氧化物)
Primary ozonide (molozonide)
双键断开,两端各成羰基
The C=C is cut; each end becomes a carbonyl
年表Timeline
- 1840
舍恩拜因发现臭氧
Schönbein discovers ozone
- 1903
哈里斯系统研究臭氧化
Harries studies ozonolysis systematically
- 1949
克里吉提出机理
Criegee proposes the mechanism