Organic Question

[Guest Snew]

For all you organic buffs out there: what is the difference between torsional and steric strain? I can see from their definitions that they are different, but it just looks to me like they both boil down to "large substituents like to be as far apart as possible."

 

Could anyone clarify this for me?

 

Thanks,

Snew

[Guest Kirsteen]

Hi there,

 

Basically, steric strain is more of a holistic or overall strain within a molecule, i.e., a sum of all types of strains all of which are caused by the clashing of molecules' electron clouds. Torsional strain is one particular type of strain, (others are angular and Van der Waals) and it is specifically caused by interactions of the electron clouds of two nascent atoms that are bonded to one another. An example of a molecule that changes conformation to reduce torsional (and thus steric) strain is cyclohexane. In one of its conformations (chair) it can reduce the clashing of electron clouds of nascent carbon atoms, which also helps to reduce its overall, steric strain.

 

Hope that helps.

 

Cheers,

Kirsteen

[Guest Snew]

Thanks Kirsteen, that was very helpful