Can anyone explain what Huckel's Rule is in regards to determining whether a compound is aromatic or not?
Thanks
Thanks
Huckel's Rule (4n+2)
- Thread starter CSade469
- Start date
- Joined
- Apr 8, 2007
- Messages
- 361
- Reaction score
- 0
Wikipedia pretty good: http://en.wikipedia.org/wiki/Hückel's_rule
A little hint: if the nitrogen or whatever in the ring has a lone pair of electrons on it, only count those electrons if the nitrogen or whatever DOES NOT have a double bond touching it.
if the N has a lone pair but also has one or two double bonds, DO NOT count them.
good luck
A little hint: if the nitrogen or whatever in the ring has a lone pair of electrons on it, only count those electrons if the nitrogen or whatever DOES NOT have a double bond touching it.
if the N has a lone pair but also has one or two double bonds, DO NOT count them.
good luck
- Joined
- Feb 8, 2008
- Messages
- 636
- Reaction score
- 0
Just to elaborate on the 2, 6, 10 ,14...
Like ak47 said sometimes you dont count the lone pairs other times you do. So you take all the pi electrons and lone pairs (when applicable to be included) and set them equal to 4n+2 electrons. For example the number 10 is a huckel number because 4n+2=10 n=2 and as long as n=0,1,2..(an integer) it passes the test.
Like ak47 said sometimes you dont count the lone pairs other times you do. So you take all the pi electrons and lone pairs (when applicable to be included) and set them equal to 4n+2 electrons. For example the number 10 is a huckel number because 4n+2=10 n=2 and as long as n=0,1,2..(an integer) it passes the test.
- Joined
- Aug 2, 2007
- Messages
- 1,394
- Reaction score
- 3
Just because something passes huckel's rule doesn't mean it is always aromatic. You also must make sure it is planar.
- Joined
- Mar 13, 2006
- Messages
- 3,237
- Reaction score
- 22
Just to add: it has to be cyclic and conjugated also.
- Joined
- Mar 13, 2006
- Messages
- 3,237
- Reaction score
- 22
If the compound is neither anti-aromatic or aromatic, then it's got to be non-aromatic.
For a compound to be anti, these must happen.
1. Planar.
2. Conguated double bonds.
3. Cyclic.
4. Follows 4N instead of 4N+2 rule.
- Joined
- Mar 13, 2006
- Messages
- 3,237
- Reaction score
- 22
- Joined
- Jun 30, 2005
- Messages
- 2,780
- Reaction score
- 2
how do we know whether something is planar or not?
- Joined
- Aug 2, 2007
- Messages
- 1,394
- Reaction score
- 3
planar molecules are sp2.
- Joined
- Apr 25, 2006
- Messages
- 1,084
- Reaction score
- 0
Yes. Aren't you impressed by my big brain?
- Joined
- Mar 13, 2006
- Messages
- 3,237
- Reaction score
- 22
- Joined
- Mar 13, 2006
- Messages
- 3,237
- Reaction score
- 22
I knew it!
Good luck on your DAT next week. You know Formosa Chang is rooting for you.
- Joined
- Apr 25, 2006
- Messages
- 1,084
- Reaction score
- 0
Thanks hun.
- Joined
- Nov 28, 2007
- Messages
- 101
- Reaction score
- 0
Quick Q....i know the criteria for Huckels rule, but one thing that is a thorn in my side is the substituent that is connected to the ring. Will that matter if it its planer or not? Of course it being not a ring. Basically if you have a benzene ring connected to a t-butile. Is it considered aromatic? I know its planer, all bond are SP2, N= 1. But the T-butile, does it have a say in the ring being aromatic or not?
- Joined
- Oct 10, 2007
- Messages
- 1,079
- Reaction score
- 34
the substituents don't matter unless they disrupt the cyclical conjugation of the ring causing a conformatinal change in its structure.
- Joined
- Jun 30, 2005
- Messages
- 2,780
- Reaction score
- 2
I thought planar is aromatic, not anti aromatic.
- Joined
- Jan 23, 2007
- Messages
- 28
- Reaction score
- 0
Both aromatic and anti-aromatic are planar. If its non planar its non-aromatic.
It has to first meet these 3 rules to be considered aromtic or anti-aromatic
1. Planar.
2. Conguated double bonds.
3. Cyclic.
If any of those are not met its non-aromatic
Then,
4n+2 = aromtic
4n = anti-aromatic
It has to first meet these 3 rules to be considered aromtic or anti-aromatic
1. Planar.
2. Conguated double bonds.
3. Cyclic.
If any of those are not met its non-aromatic
Then,
4n+2 = aromtic
4n = anti-aromatic
Why is aniline aromatic according to Huckel's rule? When I draw the structure out, I see six pi electrons around the benzene ring, and 2 pi electrons on the nitrogen (which is sp2 hybridized). This gives me a total of 8 pi electrons.
With 8 pi electrons, I find that aniline is antiaromatic. Where am I going wrong??
With 8 pi electrons, I find that aniline is antiaromatic. Where am I going wrong??
