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Chemistry 14C Course Web Page > Forums > Concept Focus Questions > CFQ #2, regarding energy differences
 
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jathavale
Registered: 10/24/09
Posts: 8

    10/24/09 at 02:52 PM
Reply with quote#1

The solution to this problem (found on page 51 in the thinkbook) states, "Assuming the destabilization due to torsional strain (of the cis vs. trans 1,3-butadiene) does not outweigh the increase in stability due to conjugation..." Are we correct in always making this assumption? (ie are there instances in which the difference in energy between the cis and trans do trump the added stability of conjugation?)
CCW
Registered: 10/03/09
Posts: 9

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    10/24/09 at 05:31 PM
Reply with quote#2

i think it's safe to make the assumption...

conjugations significantly increase stability more than torsional strain decreases. take a look at lecture sup pg 28.
torsional strain, for the most part, is not huge (delta H falls in incriments of 1-3 kcals per mol whereas the 1-ethyne yielded a much larger difference (delta H 6-10 kcals per mol)



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