# Orgo Question

In order to determine if a molecular is aromatic, besides the physical properties i.e cyclical and conjugated, there needs to be 4n+1 pi elections. what is n?

Any positive integer

But how can you know what is the correct integer from the picture of the molecule?

I’m smiling because I had that same conversation with my organic professor and the whole idea seemed pretty stupid to me at first! But then I caught on.
Huckel’s Rule is based on molecular orbital theory. The number of pi electrons must be equal to 4n+2 where n can be any whole number (0 or any positive integer). Basically, there is no “correct” n. It can be any whole number. The n does not correspond to anything in the structure. So if 10 pi electrons (can also include lone pairs) are present, Huckel’s Rule is followed since, when n=2, you get 10 [4(2)+2). The same is true for 2 pi electrons [4(0)+2 where n=0]. However, 8 pi electrons does not follow the rule since n would have to be equal to 1.5 (8=4n+2; n=1.5).
Hope this helps!
Larry

So basically, I count the number of C=C and multiple by 2. Then add, any extra non bonding electrons that make the molecule -'ve. I plug this number in as the result and solve for n. If n is a whole number then the molecule is aromatic?

Quote:

So basically, I count the number of C=C and multiple by 2. Then add, any extra non bonding electrons that make the molecule -'ve. I plug this number in as the result and solve for n. If n is a whole number then the molecule is aromatic?

Yes, as long as the molecule is also cyclic, fully conjugated (has an unhybridized p-orbital on every atom in the ring), and planar.

during the hydolysis of anhydrides, do you always get 2 carboxylic acids?

Gabe,
You don’t have to post your questions here and again on SDN. I already answered you in the MCAT subforum.
http://forums.studentdoctor.net/showpost.php?p=3447290&postcount=142

Q of Quimica, I would disagree about posting here and SDN. Some of the OPM members don’t participate in SDN. So, what can it hurt?

(shrug) It doesn’t “hurt” anything. I just don’t understand the purpose of it.

Quote:

Q of Quimica, I would disagree about posting here and SDN. Some of the OPM members don’t participate in SDN. So, what can it hurt?

While Q is a tremendous resource to both OPM and SDN, I have to agree that posting here is also a good idea. Sometimes it’s just nice to be able to ask a question in an uncompetitive environment like the one here.

There are some on OPM that don’t peruse the SDN network, but I know Gabe posts on both - that’s probably why Q put that out there.
I guess there are some here that might benefit from that question that don’t look at the SDN posts, but SDN has a very detailed MCAT forum with people from all parts of the application process (not just non-trads) posting questions.
No big deal.

lol, I didn’t mean to start a controversy with my comment. I just didn’t know why he was posting the same question twice in both places. And I’m certainly not suggesting that he’s doing anything wrong by doing that. I just wanted him to know that he doesn’t HAVE to post every question twice.

Sorry if I put Q in a corner. I did not mean it.