Winter 2013 Final 8B

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nicoleclarke_lec1M
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Joined: Sat Jul 09, 2016 3:00 am

Winter 2013 Final 8B

Postby nicoleclarke_lec1M » Thu Mar 16, 2017 12:15 am

Why would both substiuent groups be in equatorial positions in the chair cyclohexane conformation in a cis isomer? I thought we had learned in lecture that cis isomers are always (a,e) or (e,a) meaning one is equatorial and one is axial. Please someone explain?

Selina_Han_3I
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Joined: Wed Sep 21, 2016 2:59 pm

Re: Winter 2013 Final 8B

Postby Selina_Han_3I » Thu Mar 16, 2017 12:28 am

What you recalled in lecture is correct; however, in lecture, we discussed cis isomers with substituents attached to carbons 1 and 4. In cis-1-chloro-3-ethylcyclohexane, the substituents are connected to carbons 1 and 3. Cis means that both substituents will be on the same side, and therefore pointing in the same direction (both pointing up or both pointing down). So, in the diagram, carbons 1 and 3 have axial up and equitorial down positions. The chlorine and the ethyl substituents will point up in the axial position, rather than point down in the equitorial position to reduce steric strain.

Brian Devlin 3B
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Joined: Sat Oct 08, 2016 3:01 am

Re: Winter 2013 Final 8B

Postby Brian Devlin 3B » Sat Mar 18, 2017 4:39 pm

How would you describe trans-1-chloro-3-ethylcyclohexane?

nicoleclarke_lec1M
Posts: 25
Joined: Sat Jul 09, 2016 3:00 am

Re: Winter 2013 Final 8B

Postby nicoleclarke_lec1M » Sun Mar 19, 2017 9:17 am

the trans molecule would have one in the equatorial position and one in the axial position. Since the ethyl substituent take priority, it will be in the equatorial position.


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