DAT Destroyer Orgo Question

[ASOT]

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Hey guys, not sure if I'm having a major brain fart right now or if the answer key for destroyer is off but can someone please explain to me how A has 5 pi bonds, C has 6 pi bonds and E has 7 pi bonds. I see one less in each of those choices. Is there something special with the conjugation that adds an additional pi? An explanation would be greatly appreciated 🙂 Thanks in advance.

 

[Myce]

Hey guys, not sure if I'm having a major brain fart right now or if the answer key for destroyer is off but can someone please explain to me how A has 5 pi bonds, C has 6 pi bonds and E has 7 pi bonds. I see one less in each of those choices. Is there something special with the conjugation that adds an additional pi? An explanation would be greatly appreciated 🙂 Thanks in advance.

A has 4 pi bonds because there are 4 double bonds-- the CHO has a C=O along with the 3 double bonds in the benzene ring. C has a total of 6 pi bonds because the triple bond has 2 pi bonds and 1 sigma bond along with the other 3 pi bonds from the ring (2 from the triple bond and 3 from the benzene ring). E is also the same as C. Remember that triple bonds = 1 sigma bond and 2 pi bonds. Hopefully that helps!

 

[ASOT]

A has 4 pi bonds because there are 4 double bonds-- the CHO has a C=O along with the 3 double bonds in the benzene ring. C has a total of 6 pi bonds because the triple bond has 2 pi bonds and 1 sigma bond along with the other 3 pi bonds from the ring (2 from the triple bond and 3 from the benzene ring). E is also the same as C. Remember that triple bonds = 1 sigma bond and 2 pi bonds. Hopefully that helps!

Haha yeah, that's what I thought which is why I marked those on the question BUT the answer key says that A has 5, C has 6, and E has 7. I wasn't too sure of myself before, but now I'm just going to assume that there is an error in the key for that question because it really makes no sense to me/anyone I have asked. Thank you anyway!

 

[Futuredentguy2015]

A has 5 pi bonds, because you also count the ring as well. So not only the 3 Pi bonds in the ring and the CHO bonds (4 total) but also the hexane ring. I'm thinking this is the case from what Chad mentioned when he was going over unsaturation. Same with the other ones, the rings all add an additional pi bond.

 

[Myce]

Haha yeah, that's what I thought which is why I marked those on the question BUT the answer key says that A has 5, C has 6, and E has 7. I wasn't too sure of myself before, but now I'm just going to assume that there is an error in the key for that question because it really makes no sense to me/anyone I have asked. Thank you anyway!

Sorry, I misread your question, and tried to re-explain what you already know. I thought the numbers that you wrote down were the answers. I looked at the problems some more and couldn't figure out where the extra pi bonds are coming from. Sorry.

 

[ASOT]

Sorry, I misread your question, and tried to re-explain what you already know. I thought the numbers that you wrote down were the answers. I looked at the problems some more and couldn't figure out where the extra pi bonds are coming from. Sorry.

No its ok, thanks for trying to help 🙂

A has 5 pi bonds, because you also count the ring as well. So not only the 3 Pi bonds in the ring and the CHO bonds (4 total) but also the hexane ring. I'm thinking this is the case from what Chad mentioned when he was going over unsaturation. Same with the other ones, the rings all add an additional pi bond.

Wait so the benzene ring has 4 pi bonds?? Are you sure because I feel like I ALWAYS learned that benzene had 3. Can you please explain, sorry I just really want to understand why

 

[Myce]

A has 5 pi bonds, because you also count the ring as well. So not only the 3 Pi bonds in the ring and the CHO bonds (4 total) but also the hexane ring. I'm thinking this is the case from what Chad mentioned when he was going over unsaturation. Same with the other ones, the rings all add an additional pi bond.

A ring counts as 1 degree of unsaturation, like a pi bond, but I don't think it counts as a pi bond. Take cyclopropane for example. It only has 1 degree of unsaturation and no pi bonds.

 

[youngy]

A ring counts as 1 degree of unsaturation, like a pi bond, but I don't think it counts as a pi bond. Take cyclopropane for example. It only has 1 degree of unsaturation and no pi bonds.

right, having a degree of unsaturation doesn't mean you automatically have pi bond. You need to have a p-orbital overlap to have pi bond, and if you look at plain old cyclohexane, it has a degree of unsaturation, but no p orbitals, all SP3 orbitals and S orbitals for Hydrogens.


So, it is
A= 4 pi
C= 5pi
E= 6pi