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醛肟和酮肟

(英语:oxime)是一类具有通式R1R2C=NOH的有机化合物。如果R1或R2之一是,则该肟被称为醛肟;否则称为酮肟。由于上有一对孤对电子,肟有两个异构体:顺式和反式。除芳香醛肟(大基团)外,醛肟都以顺式存在;而酮肟的两种异构体则基本上可以分离出来。

肟大多具有良好的结晶,不溶于水,熔点也比较确定,因此可根据肟的熔点来确定醛或酮。丁二酮肟是用来鉴定离子的试剂。

合成

肟可以由羟胺反应得到,肟水解可以得到相应的醛或酮。除此之外,肟还可以由亚硝酸酯亚硝酸异戊酯和含活泼氢的化合物反应制得,如乙酰乙酸乙酯亚硝酸钠乙酸中反应、[1][2]亚硝酸乙酯甲乙酮盐酸中反应[3]以及苯丙酮[4]氯乙酰苯[5]丙二腈[6]和亚硝酸钠的类似反应。

反应

酸性催化剂硫酸多聚磷酸以及能产生强酸五氯化磷三氯化磷苯磺酰氯亚硫酰氯等催化下,酮肟可以发生Beckmann重排反应生成酰胺。工业上制取己内酰胺即是利用该反应,而己内酰胺是制取尼龙-6的原料。利用该反应也可以由水解产物推知原料肟的构型。

肟也可以被钠汞齐氢化还原,生成

醛肟可以在一些强碱酰胺以及低价磷化合物等的作用下脱去一分子水,变为[7]

-CH=NOH → -C≡N + H2O

参见

参考资料

  1. ^ Hans Fischer (1943). "2,4-Dimethyl-3,5-dicarbethoxypyrrole". Org. Synth.; Coll. Vol. 2: 202. 
  2. ^ Hans Fischer (1955). "Kryptopyrrole". Org. Synth.; Coll. Vol. 3: 513. 
  3. ^ W. L. Semon and V. R. Damerell (1943). "Dimethoxyglyoxime". Org. Synth.; Coll. Vol. 2: 204. 
  4. ^ Walter H. Hartung and Frank Crossley (1943). "Isonitrosopropiophenone". Org. Synth.; Coll. Vol. 2: 363. 
  5. ^ Nathan Levin and Walter H. Hartung (1955). "ω-chloroisonitrosoacetophenone". Org. Synth.; Coll. Vol. = 3: 191. 
  6. ^ J. P. Ferris, R. A. Sanchez, and R. W. Mancuso (1973). "p-toluenesulfonate". Org. Synth.; Coll. Vol. 5: 32. 
  7. ^ 赵文超. 醛肟脱水试剂. 化学试剂. 1997, (19(5)): 273–280. 
  • 邢其毅等. 《基础有机化学》第三版上册. 北京:高等教育出版社,2005年. p516. ISBN 7-04-016637-2
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