steric strian....

[theedaddy77]

SO according to blue book eclipsed is 120 degrees apart, and guage is liek 60 degrees and total eclpised is 0. (i know it doesnt make sense but check the books and it is right)

so im taking a achiever and the question is..

Which of the following conformations produces highest steric strain in butane, C4H10?



A. Anti
B. Gauche
C. Eclipsed
D. Staggered
E. None of the above

it it says it is C.... anyone know why>.?

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[userah]

anti and gauche are staggered and then you have eclipsed and totally eclipsed. anti is when you have the methyl groups 180 degrees apart and gauche is when they're 60 degrees apart i believe. eclipsed produces the highest strain; that's when they're overlapping.

here's a website that might help you clear up any confusion you might have
http://www.cem.msu.edu/~reusch/VirtTxtJml/sterisom.htm

good luck =)

 

[Sea of ASH]

you said eclipse is 0 degrees apart right? then they are aligned which produces highest steric strain

 

[theedaddy77]

here is the thing though Kaplan made a distinction between eclipsed and total eclipsed, eclipsed was just 120 degrees apart while total eclipsed was 0. so why would it choose eclippsed when that is 120 degrees apart?

 

[BahamaTodd]

Kaplan makes the distinction of eclipsed and totally eclipsed to show that there are two "levels" of eclipsed conformations.

Steric hinderance in the eclipsed conformation comes from the molecules in two adjacent carbons lining up. Steric hinderance in the totally eclipsed conformation comes from the the two end methyl groups being aligned.

Even though there are two levels of eclipsed conformations, they both cause more strain than gauche or anti conformations. The exam question just grouped all the eclipsed together.