HW Question: 1.21

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Steph S 2F
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Joined: Fri Sep 26, 2014 2:02 pm

HW Question: 1.21

Postby Steph S 2F » Mon Feb 29, 2016 6:28 pm

The answer given states that the name of the cycloalkene is 5-methycyclopenta-1,3-diene. However if we want to number the carbon atoms so that the sum is the smallest possible sum, shouldn't the name be 2-methylcyclopenta-1,3-diene?

Michelle Pham 1G
Posts: 21
Joined: Fri Sep 25, 2015 3:00 am

Re: HW Question: 1.21

Postby Michelle Pham 1G » Mon Feb 29, 2016 7:20 pm

I believe that in lecture we learned that there is not such thing as a sum rule. Rather, we just want the lowest numbering possible.

Each tip of the pentagon represents a C. Double bonds get priority in naming versus the substituent so you want to start with the double bond. It does not matter which double bond you start with. From there, count to the next double bond, so that would be 3. Since you have to number it in the same direction, the methyl would be a 5.

Hannah Ship 2H
Posts: 15
Joined: Fri Sep 25, 2015 3:00 am

Re: HW Question: 1.21

Postby Hannah Ship 2H » Tue Mar 01, 2016 5:44 pm

For this question, why would it not be 5-methyl-1,3 cyclopentadiene?

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