Homework question

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Grace_Stevenson_1A
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Joined: Wed Sep 21, 2016 2:57 pm

Homework question

Postby Grace_Stevenson_1A » Tue Mar 14, 2017 12:55 pm

Why wouldn't this structure be Cis because the methyl and bromo group are on the same side of the double bond? Thanks!
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Alyssa Ishimoto 1A
Posts: 10
Joined: Sat Jul 09, 2016 3:00 am

Re: Homework question

Postby Alyssa Ishimoto 1A » Tue Mar 14, 2017 4:21 pm

The structure would be trans because the ethyl on the left side of the molecule has priority and the bromo group on the right side of the molecule has priority.

Grace_Bower_2B
Posts: 13
Joined: Wed Sep 21, 2016 2:58 pm

Re: Homework question

Postby Grace_Bower_2B » Wed Mar 15, 2017 3:02 pm

Why did you think the methyl group had higher priority than the ethyl group?
Z (cis) and E (trans) are determined base on the location of the highest priority substituent on either side. To determine priority you look at the atomic number of the molecular attached to the central carbon. In the case of methyl and ethyl it is the same; in that case, you go on more bond over and see that the methyl has a hydrogen (atomic 1) and the ethyl has a carbon (atomic 6). 6>1. Therefore the ethyl has a higher priority.
The ethyl and bromine are on opposite corners so it is Trans (E)


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