Aromaticity for a bigger ring

[RCT PC CRN]

Advertisement - Members don't see this ad

Planar vs. Non-planar

Will DAT mention whether the bigger ring (more then 5-6 C) is planar or non-planar?

Or we need to know the shape in advance for bigger ring.

E.g. Cyclooctatetrane is not aromatic even though it is cyclic, conjugated and obey huckel's rule cause it resembles tub shaped not planar. Obviously on printed paper or computer screen you don't see that.

My Orgo prof's rule was assume all given compound is planar unless it specifically mentioned otherwise. How about DAT?

 

[UndergradGuy7]

Mine didn't have any big rings.

If it did, I would assume nonplanar unless stated in the question that it is planar. Just my opinion though...

 

[duodenum]

chads video stated that in order to be planar it must be 7 atoms or smaller, thats what i go by on all of my practices

 

[RCT PC CRN]

chads video stated that in order to be planar it must be 7 atoms or smaller, thats what i go by on all of my practices

Some example of aromatic compound. [14]-annulene, [18]-annulene. Both has way more carbon then 5-6...14 and 18 respectively.

I so hope DAT people go little easy with me. I hate ambiguity.😡

 

[orgohacks]

Planar vs. Non-planar

Will DAT mention whether the bigger ring (more then 5-6 C) is planar or non-planar?

Or we need to know the shape in advance for bigger ring.

E.g. Cyclooctatetrane is not aromatic even though it is cyclic, conjugated and obey huckel's rule cause it resembles tub shaped not planar. Obviously on printed paper or computer screen you don't see that.

My Orgo prof's rule was assume all given compound is planar unless it specifically mentioned otherwise. How about DAT?

Just an FYI - Cyclooctatetraene *doesn't* obey Huckels' rule - that's why it's not aromatic, and also why it's tub-shaped and not flat.

4n+2 (huckel's rule) is the key thing to consider when answering these types of questions.

 

[RCT PC CRN]

Just an FYI - Cyclooctatetraene *doesn't* obey Huckels' rule - that's why it's not aromatic, and also why it's tub-shaped and not flat.

4n+2 (huckel's rule) is the key thing to consider when answering these types of questions.

Yes, you are absolutely right. Cyclooctatetraene does not obey Huckel's rule but it is tub shaped though (stright out of text book). Anyways that's not the main concern though.

I would like to know whether DAT Q tells you the compound is planer or non-planar or you need know general shape. For instance, [10]-annulene (or may be its image given) aromatic or non aromatic? Looking at it. It's cyclic, conjugated, 10 pi e so obey huckel's rule but still it's not aromatic. Planar [10]-annulene would place two H atom inside the ring too close to each other so the ring puckers to relieve this strain. Thus, it is not planar. In contrast 14 and 18 are planar and thus aromatic. So here it boils down to planar vs. Non planar and my concern is whether that information been provided to you or you need to know those shape.

P.s. I do agree 4n+2 is most important though.

 

[orgohacks]

Yes, you are absolutely right. Cyclooctatetraene does not obey Huckel's rule but it is tub shaped though (stright out of text book). Anyways that's not the main concern though.

I would like to know whether DAT Q tells you the compound is planer or non-planar or you need know general shape. For instance, [10]-annulene (or may be its image given) aromatic or non aromatic? Looking at it. It's cyclic, conjugated, 10 pi e so obey huckel's rule but still it's not aromatic. Planar [10]-annulene would place two H atom inside the ring too close to each other so the ring puckers to relieve this strain. Thus, it is not planar. In contrast 14 and 18 are planar and thus aromatic. So here it boils down to planar vs. Non planar and my concern is whether that information been provided to you or you need to know those shape.

P.s. I do agree 4n+2 is most important though.

I say this without any special knowledge of the DAT, but I strongly doubt you'd be expected to know about how [10] annulene isn't flat because of the transannular strain. A lot of organic chemists couldn't even tell you that (but they could tell you that 10 is a huckel number, that aromatic compounds are cyclic, conjugated, flat, etc). Probably safe to let it pass.

 

[RCT PC CRN]

I say this without any special knowledge of the DAT, but I strongly doubt you'd be expected to know about how [10] annulene isn't flat because of the transannular strain. A lot of organic chemists couldn't even tell you that (but they could tell you that 10 is a huckel number, that aromatic compounds are cyclic, conjugated, flat, etc). Probably safe to let it pass.

Thnx for your response. I appreciate it

 

[mprs]

The question will be designed so you don't really need to know. All rings above 7C on my test were obviously not aromatic due to other reasons.