Difference Between Primary and Secondary Allylic Carbocations

Thekey differencebetween primary and secondary allylic carbocations is thatprimary allylic carbocation is less stable than secondary allylic carbocation.

一个基地lylic carbocation is a resonance stabilized carbon structure. It is an ion containing a positive charge. In these ions, the positive ion is placed on the allylic carbon atom (an allylic carbon atom is the adjacent atom to a double bond). Primary allylic carbocation is an allylic carbocation where the positive charge is placed on a primary carbon atom while secondary allylic carbocation is an allylic carbocation where the positive charge is placed on a secondary carbon atom.

内容

1.Overview and Key Difference
2.什么是主要的烯丙基碳化物
3.What are Secondary Allylic Carbocations
4.并排比较 - 表格形式的初级与次级烯丙基碳化
5.概括

什么是主要的烯丙基碳化物?

Primary allylic carbocation is an allylic carbocation where the positive charge is placed on a primary carbon atom. It is named as a carbocation because it contains a positive charge on a carbon atom. Usually, an allylic carbocation carries a +1 positive charge. A primary carbon atom is a carbon atom that is attached to twohydrogen atoms和double bond. Typically, a neutral carbon atom forms four covalent bonds, and one covalent bond is removed when it forms a cation. A primary carbon atom contains only onearyl or alkylgroup attached to it while other bonds are C-H bonds.

Difference Between Primary and Secondary Allylic Carbocations

图01：烯丙基共振

Generally, a molecule containing double bonds between carbon atoms can have resonance stabilized structures. Resonance means that electrons in the pi bond of the double bond are distributed throughout the molecule as a delocalized system where the stability is increased than in a normal molecule. Therefore, if we are going to name a compound as a primary allylic carbocation, that particular compound should have a positive charge on allylic carbon atoms in all possible resonance structure of that molecule.

什么是次级烯丙基碳化碳？

Secondary allylic carbocation is an allylic carbocation where the positive charge is placed on a secondary carbon atom. It is named as a carbocation because it contains a positive charge on a carbon atom. Usually, an allylic carbocation carries a +1 positive charge. A secondary carbon atom is a carbon atom that is attached to one hydrogen atom, a double bond and an alkyl or aryl group. Typically, a neutral carbon atom forms four covalent bonds where one covalent bond is removed when it forms a cation. A secondary carbon atom contains two aryl or alkyl group attached to it while the other bond is a C-H bonds.

Sometimes, the term secondary allylic carbocation is used when only one resonance structure of a particular compound contains the positive charge on a secondary carbon atom. More importantly, secondary allylic carbocations are more stable than primary allylic carbocations because they have two aryl or alkyl groups attached to the carbon atom bearing the positive charge (aryl or alkyl groups are electron-withdrawing groups so, they can minimize the positive charge on the carbon atom).

初级和次级烯丙基碳化碳有什么区别？

烯丙基碳水化合物是化学结构，其中正电荷位于分子的烯丙基碳原子上。烯丙基碳原子是与双键相邻的碳原子。Primary allylic carbocation is an allylic carbocation where the positive charge is placed on a primary carbon atom while secondary allylic carbocation is an allylic carbocation where the positive charge is placed on a secondary carbon atom. The key difference between primary and secondary allylic carbocations is that the primary allylic carbocation is less stable than the secondary allylic carbocation.

下图总结了主要和次级烯丙基碳化碳之间的差异。