Torsional and steric strain #3.9

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Isha Bagga 3J
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Torsional and steric strain #3.9

Postby Isha Bagga 3J » Thu Mar 05, 2015 10:06 pm

For question 9 in chapter 3 of the organic chemistry workbook, how do you know that there is torsional and steric strain? For the torsional strain, are the two CH2 parts eclipsed?

martha-1I
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Re: Torsional and steric strain #3.9

Postby martha-1I » Fri Mar 06, 2015 10:28 am

You can see that there is steric and torsional strain once you draw the lewis structure for molecules given. You will notice that the hydrogens in the H2C-CH2 are eclipsed and the carbon atoms are adjacent each other which gives it a torsional strain. When you move up on the molecule you will see that there are two hydrogens that want to occupy the same location which makes this interaction steric. I will post a picture of this to give you a visual in a coupe of minutes once I draw it.

martha-1I
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Re: Torsional and steric strain #3.9

Postby martha-1I » Fri Mar 06, 2015 10:48 am

Attached is a picture explaining why the unfavorable interactions in this question are steric and torsional.
Attachments
20150306_104420.jpg
Steric and Torsional interaction

Chem_Mod
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Re: Torsional and steric strain #3.9

Postby Chem_Mod » Tue Mar 10, 2015 2:57 pm

Well done Martha!

LeilaBushweller1F
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Re: Torsional and steric strain #3.9

Postby LeilaBushweller1F » Wed Mar 11, 2015 10:36 am

How do you know that the substituent groups are both on the top of the carbons, rather than opposite of each other (one on the top of a carbon, the other on the bottom)?

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Re: Torsional and steric strain #3.9

Postby Chem_Mod » Wed Mar 11, 2015 11:27 am

you need to draw Newmann projection througn C2-C3 axis to view it. When two large groups (CH2F and CH2CH3) are eclipsed in the Newmann, you will observe the steric and torsional strain as Martha described.

Justin Le 2I
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Re: Torsional and steric strain #3.9

Postby Justin Le 2I » Wed Mar 11, 2015 10:07 pm

You can tell by looking at the Lewis structure. In this case, both of them are on top.


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