Z-1-chloro-2-methyl-1-butene

[Yinhan_Liu_1D]

On our textbook, page16, rule 5: the group that bounds to the second Csp2 is CH2CH3.

Why is it Z-1-chloro-2-methyl-1-butene but not Z-1-chloro-2-methylene-1-butene or Z-1-chloro-2-ethyl-1-butene??

If it counts the group that directly bounds to C, it should be "methylene"; if it counts the group that bounds to the C as a whole, it should be "ethyl". Isn't it? I would appreciate your help!

[Maggie Bui 1H]

It is not methylene because methylene refers to a group in the middle of the carbon chain (-CH2-). The CH3 attached to one of the carbons in the double bond is a substituent by the rule that is discussed in this section, and is therefore called a methyl group.

There is no "ethyl" in the name because the CH2CH3 is part of the main chain by the rule discussed in this section. If we were to call the CH2CH3 in this example an ethyl group, you would also have to change the name of the main chain (from butene) because we would not count the carbons in CH2CH3 as carbons that go into the name of the main chain.

[Yinhan_Liu_1D]

It is not methylene because methylene refers to a group in the middle of the carbon chain (-CH2-). The CH3 attached to one of the carbons in the double bond is a substituent by the rule that is discussed in this section, and is therefore called a methyl group.

There is no "ethyl" in the name because the CH2CH3 is part of the main chain by the rule discussed in this section. If we were to call the CH2CH3 in this example an ethyl group, you would also have to change the name of the main chain (from butene) because we would not count the carbons in CH2CH3 as carbons that go into the name of the main chain.

Thank you, I understand now. I must have forgotten this rule when I was reading this part.