steric strain vs torsional strain

[akimhaneul]

I'm having trouble understanding the difference between these two terms. Can anyone explain?

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[Bersabeh]

I'm having trouble understanding the difference between these two terms. Can anyone explain?

torsional strain is increase in potential energy due to repulsion, its related to anti-eclipsed,ecllipsed etc. steric strain is strain due to geometry of the molecule, eg: 2 bulky grps aligned together.

 

[DAT Destroyer]

I'm having trouble understanding the difference between these two terms. Can anyone explain?

This is a tough question.....many professors even have fights over it !!!! Steric strain refers to when atoms are essentially very close, and begin to cause a repulsion on one another. It is due to the atom proximity . When dealing with TORSIONAL strain......we have the BONDS eclipsing one another. Thus if we have two methyl groups eclipsing each other......we have BOTH strains. First...the atoms are in each others way.....this is the steric strain. Secondly the BONDS are eclipsing each other . This is torsional. A model would easily show this. Now lets consider the 60 degree rotation into the gauche conformation. We have only a bit....about 1 kcal of STERIC strain, but no torsional strain since the bonds do not eclipse.

Hope this helps.

Dr. Romano

 

[seaweed1]

I always remember it as:
steric strain = due to electron clouds being too close
torsional = due to bonds being too close