In Section 1.12 we discussed the effect that branching can have on the boiling point of a compound. In certain instances, branching may also affect how a molecule can react with different molecules. We use the term “steric hindrance” to describe how branching can influence reactivity. For example, greater “steric crowding” may decrease the reactivity of a C=C π bond (Org. Lett. 1999, 1, 1123–1125). In the following molecule, identify each π bond and determine which has a greater degree of steric crowding. (Note: This is not the same as “steric number”.)
Hey guys. So, in this problem we need to figure out which one of these double bonds has the greatest steric crowding, okay? So, another way we can think about this is just by how highly substituted a double bond is, right? So, let me show you what I mean by that, okay? So if we have a double bond like this, right? And then we have an R group attached we would say this is mono substituted, okay? If we have a double bond and we have two groups attached we would say this is a disubstituted, okay? And this also works if we have it like this, you know, with one group on one side and the other on the other, okay? like that and if we have something like this, you know, you get the idea, we get triple, trisubstituted, right? So we have something looks like that, right? And we can have something like that which is going to be tetra substituted, right? So guys obviously as we continue moving forward we have more crowding, right? Because we've got more groups attached to our double bond directly, right? So that's really what this question is asking, okay? So we need to identify, which one of these double bonds has more groups attached. So, once we identify it that way it becomes a lot simpler, right? if we look at this double bond we've only got one group directly attached by double bond, right? But if we look at this double bond how many do we have? we have 1, 2, 3, right? So guys the one on the left is, this one is, let me move out of the frame, this one is trisubstituted while this one is mono, okay? So the double bond that is more substituted is going to be this one, this one has a higher steric crowding. Alright guys. So, efficient this problem lets move forward.