All right. So is this first molecule conjugated? Does it have 3 atoms back to back that are able to resonate? And actually, what we notice about it is that it has a pi bond and a pi bond back to back, meaning this is definitely conjugated because it has 1, 2, 3, 4 atoms in a row that are of the type that I showed above. My question to you is, would this be conjugated? Absolutely. This is conjugated because it has those 4 atoms in a row. In fact, it more than meets the criteria because all we needed was 3 atoms in a row, but this one actually has 4. Okay? So let's look at this next one. Does this next one have a conjugated state or exist in a conjugated state? And it actually does because again, I have 3 atoms, at least 3 atoms that are back to back or adjacent that can resonate. We see that we have a double bond that counts as 2 and then we have a cation which counts as 3. So 1, 2, 3, which is an empty orbital, so that's a type of an empty orbital, that will be able to resonate as well, so this is also conjugated. Finally, we have this last molecule. Did you say that it was conjugated or non-conjugated or unconjugated? And the answer is that this is not conjugated. This would be, sometimes the word that's opposite of conjugated is isolated. Okay? This is an isolated molecule or not conjugated. Not conjugated. Because of the fact that I do I have 3 atoms that can resonate? Yes. I have 1-2-3. But one of my criteria is not being fulfilled. They're not all immediately next to each other. Notice how I have this atom in the middle that's messing things up. It's isolating them from being able to really delocalize with each other. Because of that, that's going to cause my isolated molecule to exist. Does that make sense? Basically, we've got 2 conjugated and one isolated.
Now I'm going to ask you a follow-up question which you don't need to know the answer for, but I'm just going to throw it out there. Out of the 2 conjugated molecules, which one would we expect to have the higher wavelength in a UV Vis spectrometer? Would you expect compound 1 to have the higher wavelength or compound 2 to have the higher wavelength? The answer is compound 1 because compound 1 is more conjugated than compound 2. What we see is that compound 1 has 4 atoms that are able to resonate back to back whereas 2 only has 3. Since 4 is bigger than 3, that means that we would expect it to have a bigger wavelength and we would expect this one to have a smaller wavelength. That's just an application of what I was talking about earlier in terms of that analytical technique called UV Vis. Let's go ahead and move on to the next topic.
