Which molecule has the shortest carbon–oxygen bond? (LO 7.3, 7.9) (a) CH3OH (b) CO (c) CO2 (d) HCOOH

Video transcript

Hello. Everyone in this video we're given four different molecules that were trying to break or see which one has the shortest carbon auction bond. So carbon likes to have four bonds. Let's actually write this out. So carbon likes to have four bonds, hydrogen likes to have one bond do the to the duet role. And oxygen likes to have two bonds and two lone pairs to fulfill its octet. So just use these rules to go and apply and draw out the structures of each and every single one of these molecules starting off with molecule A. Again we have this um formula written in this compact structure. So we know what is what? So we have this carbon here connected to three high regions then continue the chain. We have another carbon now connected to two hydrogen ions. And then we have an auction connected to a hydrogen. And like I said auction likes to have two bonds and two lone pairs. So we'll add in two lone pairs. Everything does look correct according to our rules here. So that's molecule A. Moving onto molecule B. Again we have this carbon here with three different or three high regions and then we have a central oxygen connected to another terminal sage three. Again, auction likes to have two bonds and two lone pairs to go ahead and add in those two lone pairs. Next is structure C. So we have ch three C. O. H. So again we have the CH three. So our carbon connected to three high regions and now it's connected to a another carbon. So now it has two auctions connected to this uh this carbon, so one will have a double bond and one will have two sigma bonds of two single bonds because we need this terminal hydrogen. And of course we just add those two lone pairs because of this rule at the bottom here. Alright, last structure that will go ahead and draw is of carbon monoxide. So have carbon and auction. And because we don't have any other atoms, we just need a triple bond to connect those two atoms. And of course two lone pairs each. So these two lone pairs here do not really go by this here, but because we need to go ahead and fulfilled the octet rule as well as use of all the events electrons necessary. We can see here that the carbon will now have a negative one, formal charge and a hydrogen or oxygen will not have a formal charge of plus one. But these two formal charges will cancel to give us a neutral molecule, which is why this has no charge. So, what we can go ahead and kind of notice or realize from our chemistry courses is that a shorter bond means that it's going to be more stable. It is more stable. It needs to go ahead and have a higher bond order. And a higher bond order means more bonds. So that just means a triple bond is stronger than our double bond which is stronger than our single bond. So all the structures here, this one has single bonds. This one has single bonds. This one has a double bond, but this one has a triple bond, so the molecule with the shortest carbon oxygen bond is going to be our carbon monoxide here because it has a triple bond. And like I said, we know that our triple bond is a higher order of our bond. Um and that means it's more stable and that means it's the shortest. So answer D. Is going to be our final answer for this problem.