Benzene has the following structural formula.

(b) Which statement best describes the carbon–carbon bonds in benzene? (i) Three carbon–carbon bonds are longer and weaker than the other three carbon–carbon bonds. (ii) All six carbon–carbon bonds are identical, and their length and strength are between a double and single bond. (iii) The length of carbon–carbon double bond switches back and forth between the length of a double and a single bond.

Video transcript

Welcome back everyone choose the statement that correctly describes the carbon carbon bonds in nap Selene were given the molecule of naphthalene below and looking at our answer choices, we can see that they're all in reference to our carbon carbon single bonds. So we're going to recognize that each corner of the structure represents a carbon atom. And we want to recognize that we have pi bonds making up each ring of our natural in structure. And so because we have these pi bonds, they can be localized and shift to different locations. So if this pi bond shift to this location, this would cause this pi bond to have to shift here, which would cause this pi bond to have to shift here. And with these shifts we would create a second resident structure. Draw that better. Sorry about that where we have our two rings of napoli in still where in our first ring we now have the following shifts which results in the following position of pi bonds being one here, A pi bond here and then a pi bond here. We're in our second ring. We still have the same locations of our original pi bonds for the second ring because we did not shift them. However, if we were to now shift these pi bonds where this one would shift here, causing this pi bond to have to shift here, causing this pi bond to have to shift here. We would form a third resonant structure, which I'll draw actually below here for sake of room where we have our first ring of our nap Selene where we have that bonded to our second ring of naps Ellen. And sorry, in our first ring we maintain the positions of these two pi bonds as unchanged. However, this pi bond is now located here. We have a pi bond here and then we have a pi bond in this location. And so this would be our third resident structure where we want to recognize that the only resident structure where we have what we should know as a benzene ring. Specifically, We want to recall that a benzene ring is going to appear as ring one Where we have three pi bonds characterizing the ring. We have two benzene rings in our second resonance structure. We have one benzene ring here and a second benzene ring here due to that pi bond that we created in the middle here. And so because of the presence of these two benzene rings for the second resident structure, whereas our other residents structures only have one benzene ring, we would confirm that not all of our carbon carbon bonds are going to therefore be identical. And so that means that not all of the carbon carbon bonds will have equal bond length and bond strength. And so if we were to label the bond length of our bonds in nap Selene, we're going to recognize that we would have varying bond lengths. And so the only correct choice is going to be ruling out choices A. B and C. Where we would confirm that the only correct choice is going to be choice E because after we rule out choice D. All of the above, none of the above would be true. All of the carbon carbon bonds nap. Selene will not have equal bond strength because we know that they're going to have varying values of bond length, meaning that not all bonds, not all the carbon carbon bonds are going to be identical. So choice would be the best answer choice to make the most sense to complete this example. I hope that everything I reviewed was clear. If you have any questions, please, leave them down below and I'll see everyone in the next practice video.