Final 2012 6B

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James C
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Joined: Tue Jan 07, 2014 2:20 pm

Final 2012 6B

Postby James C » Sat Mar 15, 2014 8:48 pm

Question 6B on Winter 2012 Final Exam states:

"Name the following organic compounds."

The solution guide reads: 1-isopropyl-3-neopentylcyclohexane (for the first molecule)

If the organic molecule contains a cyclohexane, why do we not designate cis or trans for the compound?
Attachments
1-isopropyl-3-neopentylcyclohexane.png
1-isopropyl-3-neopentylcyclohexane

y3chem
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Re: Final 2012 6B

Postby y3chem » Sat Mar 15, 2014 8:54 pm

you designate cis or trans when you see a double bond. :)

y3chem
Posts: 174
Joined: Fri Sep 20, 2013 3:00 am

Re: Final 2012 6B

Postby y3chem » Sat Mar 15, 2014 8:56 pm

actually, yes, you should, in this case, it will be cis because 1-isopropyl-3-neopentylcyclohexane has a isopropyl on 1 and neopentyl on 3, to have a stable conformation you will have to put them in the equatorial position.
since they are one 1 and 3, the atoms are on the same side, so its cis.

i am not sure why they didn't put cis in the solution, but you should put in down in case.

James C
Posts: 17
Joined: Tue Jan 07, 2014 2:20 pm

Re: Final 2012 6B

Postby James C » Sat Mar 15, 2014 8:57 pm

I thought you listed cis or trans for double bond and cyclic structures?

James C
Posts: 17
Joined: Tue Jan 07, 2014 2:20 pm

Re: Final 2012 6B

Postby James C » Sat Mar 15, 2014 8:57 pm

@ychem

Thanks!

Chem_Mod
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Re: Final 2012 6B

Postby Chem_Mod » Sun Mar 16, 2014 8:53 am

This molecule was drawn without designating the direction (up or down) of the two functional groups. Therefore, we cannot stipulate cis or trans in the name because we do not have that information.

y3chem wrote:in this case, it will be cis because 1-isopropyl-3-neopentylcyclohexane has a isopropyl on 1 and neopentyl on 3, to have a stable conformation.
Not necessarily. We cannot assume that the molecule is in this conformation based on the given structure. Only if the structure had been drawn using wedges and dashes or as a chair could we designate cis or trans.

y3chem
Posts: 174
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Re: Final 2012 6B

Postby y3chem » Sun Mar 16, 2014 9:45 pm

got it. I was assuming that the question asks for the most stable conformation. :)


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