4-ethyl-2,2-dimethyl-hexane

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Hee Sang Kim 3L
Posts: 33
Joined: Fri Sep 25, 2015 3:00 am

4-ethyl-2,2-dimethyl-hexane

Postby Hee Sang Kim 3L » Sun Feb 28, 2016 8:43 pm

In the course reader, why is it 4-ethyl-2,2-dimethyl-hexane instead of 3-ethyl-5,5-dimethyl-hexane? why does it not follow the "1st named group gets lower number" rule? I know the course reader says "#chain to give lowest # to substituents". Does that mean since theres 2 methyl but 1 ethyl group, methyl group gets the low number priority? or is it because 2,2,4 are generally lower than 3,5,5? How do you set standards

LinaLi2E
Posts: 22
Joined: Fri Sep 25, 2015 3:00 am

Re: 4-ethyl-2,2-dimethyl-hexane

Postby LinaLi2E » Sun Feb 28, 2016 9:38 pm

The reason why it is 4,2,2 and not 3,5,5 is because the numbers are lower overall. For the rule that says that the first named substituent gets the lower number is only when the numbers are the same. For example if you start count from the right, the numbers are 3,5 and if you start counting from the left and the numbers are still 3,5, then the substituent that is named first gets the lower number -- 3.


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