请问Hofmann消除只得是什么？cope消除和hofmann消除区别「知识普及」

Hofmann消除 反应，也称彻底甲基化反应，是胺与过量碘甲烷、氧化银和水共热时，生成三级胺和烯烃的反应。反应中间产物是四级铵碱。

不对称胺反应时，反应由动力学控制，较少烷基取代的β-碳上的氢由于酸性较强，位阻较小，因此优先被消除，产物主要是不稳定的取代较少的烯烃。

霍夫曼消除可用于合成用其他方法难以合成的烯烃。由于一级、二级和三级胺引入的甲基数目不一样，故也可通过引入的甲基数目，来判断反应物是哪一级的胺。

【英文介绍/For English】：

Hofmann elimination reaction, also known as complete methylation reaction, is a reaction in which amines are heated together with excess methyl iodide, silver oxide and water to form tertiary amines and alkenes. The reaction intermediate is a quaternary ammonium base.

In the reaction of asymmetric amines, the reaction is controlled by kinetics, and the hydrogen on the β-carbon with less alkyl substitution is preferentially eliminated due to stronger acidity and less steric hindrance, and the product is mainly unstable less substituted alkenes .

Hofmann elimination can be used to synthesize alkenes that are difficult to synthesize by other methods. Since the number of methyl groups introduced by primary, secondary and tertiary amines is different, it can also be judged which primary amine the reactant is based on the number of methyl groups introduced.