SN1和E1反应之间的差异

KeyDifference – SN1vs E1反应

SN1 reactions are substitution reactions in which new substituents are substituted by replacing existing functional groups in organic compounds. E1 reactions are elimination reactions in which existing substituents are removed from the organic compound. Thekey differencebetween SN1 and E1 reactions is thatSN1 reactions are substitution reactions whereas E1 reactions are elimination reactions.

SN1和E1反应在有机化学中非常普遍。这些反应导致通过键断裂和形成形成新化合物。

内容

1.Overview and Key Difference
2.什么是SN1反应
3.什么是E1反应
4.SN1和E1反应之间的相似之处
5。Side by Side Comparison – SN1 vs E1 Reactions in Tabular Form
6。概括

What are SN1 Reactions?

SN1 reactions are亲核取代反应在有机化合物中。这些是两步反应。因此，确定步骤的速率是碳分配形成步骤。SN1反应称为单分子取代，因为速率确定的步骤涉及一种化合物。经历SN1反应的化合物称为底物。当存在合适的亲核试剂时，从形成A的有机化合物中除去离开组碳酸化intermediate compound. Then the nucleophile is attached to the compound in the second step. This gives a new product.

The first step of an SN1 reaction is the slowest reaction while the second step is faster than the first step. The rate of the SN1 reaction depends on one reactant since it is a unimolecular reaction. SN1 reactions are common in compounds with tertiary structures. Because, higher the distribution of atoms, greater the stability of the carbocation. The carbocation intermediate is attacked by the nucleophile. That is because nucleophiles are rich with electrons and are attracted to the positive charge of the carbocation.

Polar原始溶剂诸如水和酒精会增加SN1反应的反应速率，因为这些溶剂可以促进在速率确定的步骤中形成碳定位。SN1反应的一个常见例子是hydrolysisof tert-butyl bromide in the presence of water. Here, water act as the nucleophile because the oxygen atom of the water molecule has lone electron pairs.

什么是E1反应？

E1 reactions are unimolecular elimination reactions. It is a two-step process, the first step being the rate-determining step because a carbocation intermediate is formed in the first step via leaving of a substituent. Presence of bulky groups in the starting compound facilitates the formation of carbocation. In the second step, another leaving group is removed from the compound.

The E1 reaction has two major steps named as ionization step and deprotonation step. In the ionization step, the carbocation (positively charged) is formed whereas, in the deprotonation step, a hydrogen atom is removed from the compound as a proton. Eventually, a double bond is formed between two carbon atoms from which the leaving groups were eliminated. Hence, a saturated chemical bond becomes unsaturated after the completion of the E1 reaction. Two adjacent carbon atoms of the same compound are involved in E1 reactions.

Polar protic solvents facilitate E1 reactions because polar protic solvents are favourable for the formation of carbocation. Typically, E1 reactions can be observed regarding tertiary alkyl halides having bulky substituents. E1 reactions occur in either the complete absence of bases or in the presence of weak bases.

SN1和E1反应之间有什么相似之处？

• BOT SN1和E1反应包括形成碳酸盐。
• Polar protic solvents facilitate both types of reactions.
• Both reactions are unimolecular reactions.
• Both reactions are two-step reactions.
• 两种反应都有确定的步骤。
• 更好的离去基团,反应速率越高of both SN1 and E1 Reactions.
• 对于具有三级结构的化合物，通常都可以找到SN1和E1反应。
• 两种反应的碳分配中都可以重新排列。

What is the Difference Between SN1 and E1 Reactions?

SN1与E1反应
SN1 reactions are nucleophilic substitution reactions in organic compounds.	E1 reactions are unimolecular elimination reactions.
亲核试剂的需求
SN1 reactions require a nucleophile in order to form the carbocation.	E1反应不需要亲核试剂来形成碳定位。
过程
SN1反应包括取代亲核试剂。	E1 reactions include the elimination of a functional group.
双键形成
在SN1反应中无法观察到双键形成。	A double bond is formed between two carbon atoms in E reactions.
不饱和
There is no unsaturation take place after the completion of SN1 reactions.	E1反应完成后，饱和化学物质变得不饱和。
碳原子
一个中央碳原子参与SN1反应。	Two adjacent carbon atoms of the same compound are involved in E1 reactions.

概括– SN1vs E1反应

SN1 reactions are nucleophilic substitution reactions. E1 reactions are elimination reactions. Both types of reactions are unimolecular reactions because the rate-determining step of these reactions involves a single molecule. Although these two types of reaction share many similarities, there are some differences as well. The difference between SN1 and E1 reactions is that SN1 reactions are substitution reactions whereas E1 reactions are elimination reactions.

Reference:

1.“SN1 Reaction.” Wikipedia, Wikimedia Foundation, 21 Mar. 2018.Available here
2.“ E1反应。”Chemistry libretexts，libretexts，2016年7月21日。Available here

Image Courtesy:

1.’SN1 reaction mechanism’By Calvero (Public Domain) viaCommons Wikimedia
2.“Commons Wikimedia