2 Quick Questions

[Degree]

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1) I don't understand Huckel's rule....I know that it is 4N+2 where N must be 0,1,2,3....but I don't know what N means and I don't know what a pi electron is. However, I do know what a pi bond is if they are similar? So far, I have noticed that if each double bond in a aromatic compound is given 2N then it tends to give then answer but I don't know whether that is a fluke or I don't have any explanations for it. Also, what are the other requirements for an aromatic? What does a planar structure mean?

2) For those who have used Dr.Collins self study guide, what did you think of the Verbal Ability part of the study guide? Is it a good idea to memorize the list of words or do other words usually appear on the PCAT? Basically, do the words in the study tend to appear on the PCAT?

Thanks for any responses!

 

[phathead]

For Huckle's Rule:

N is a whole number integer between 0 and 6. A ring will only be aromatic if the number of pi bonds it has is satisfied by that formula.

For instance, Benzene has six pi bonds correct? If it is aromatic, you should be able to plug in a whole number for N and have it equal 6.

It would look like: 4(1)+2 = 6 pi bonds. Since 1 is a whole, positive number, it is an aromatic compound.

If, for instance, a ring has 5 pi bonds, there is no way that a whole number can satisfy that formula, therefore it is not aromatic.

Thus
N=0, 4(0) + 2 = 2 pi bonds
N=1, 4(1) + 2 = 6 pi bonds
N=2, 4(2) + 2 = 10 pi bonds
N=3, 4(3) + 2 = 14 pi bonds
N=4, 4(4) + 2 = 18 pi bonds
N=5, 4(5) + 2 = 22 pi bonds
N=6, 4(6) + 2 = 26 pi bonds

That make sense?

 

[delano2000]

For Huckle's Rule:

N is a whole number integer between 0 and 6. A ring will only be aromatic if the number of pi bonds it has is satisfied by that formula.

For instance, Benzene has six pi bonds correct? If it is aromatic, you should be able to plug in a whole number for N and have it equal 6.

It would look like: 4(1)+2 = 6 pi bonds. Since 1 is a whole, positive number, it is an aromatic compound.

If, for instance, a ring has 5 pi bonds, there is no way that a whole number can satisfy that formula, therefore it is not aromatic.

Thus
N=0, 4(0) + 2 = 2 pi bonds
N=1, 4(1) + 2 = 6 pi bonds
N=2, 4(2) + 2 = 10 pi bonds
N=3, 4(3) + 2 = 14 pi bonds
N=4, 4(4) + 2 = 18 pi bonds
N=5, 4(5) + 2 = 22 pi bonds
N=6, 4(6) + 2 = 26 pi bonds

That make sense?

For me, I think this was the easiest thing to remember about aromaticity.

 

[b1234]

For Huckle's Rule:

N is a whole number integer between 0 and 6. A ring will only be aromatic if the number of pi bonds it has is satisfied by that formula.

For instance, Benzene has six pi bonds correct? If it is aromatic, you should be able to plug in a whole number for N and have it equal 6.

It would look like: 4(1)+2 = 6 pi bonds. Since 1 is a whole, positive number, it is an aromatic compound.

If, for instance, a ring has 5 pi bonds, there is no way that a whole number can satisfy that formula, therefore it is not aromatic.

Thus
N=0, 4(0) + 2 = 2 pi bonds
N=1, 4(1) + 2 = 6 pi bonds
N=2, 4(2) + 2 = 10 pi bonds
N=3, 4(3) + 2 = 14 pi bonds
N=4, 4(4) + 2 = 18 pi bonds
N=5, 4(5) + 2 = 22 pi bonds
N=6, 4(6) + 2 = 26 pi bonds

That make sense?

Benzene has 6 pi electrons - 3 pi bonds - pretty much everywhere you have written pi bonds you should have written pi electrons.

 

[Degree]

For Huckle's Rule:

N is a whole number integer between 0 and 6. A ring will only be aromatic if the number of pi bonds it has is satisfied by that formula.

For instance, Benzene has six pi bonds correct? If it is aromatic, you should be able to plug in a whole number for N and have it equal 6.

It would look like: 4(1)+2 = 6 pi bonds. Since 1 is a whole, positive number, it is an aromatic compound.

If, for instance, a ring has 5 pi bonds, there is no way that a whole number can satisfy that formula, therefore it is not aromatic.

Thus
N=0, 4(0) + 2 = 2 pi bonds
N=1, 4(1) + 2 = 6 pi bonds
N=2, 4(2) + 2 = 10 pi bonds
N=3, 4(3) + 2 = 14 pi bonds
N=4, 4(4) + 2 = 18 pi bonds
N=5, 4(5) + 2 = 22 pi bonds
N=6, 4(6) + 2 = 26 pi bonds

That make sense?

Yes that makes sense, thank you very much!

One last question, is Huckel's rule the only criterion needed to determine if a compound is aromatic or must the compound also satisfy other requirements? What does a 'planar' molecule mean?

Is cyclopentene aromatic?

 

[delano2000]

Yes that makes sense, thank you very much!

One last question, is Huckel's rule the only criterion needed to determine if a compound is aromatic or must the compound also satisfy other requirements? What does a 'planar' molecule mean?

Is cyclopentene aromatic?

It also has to be planar which means it has to be flat.

PS. I don't think cyclopentene is aromatic because it does not meet the Huckel rule. I think this one has 4 pi electrons so using the Huckel rule 4n+2=4, n=1/2

 

[Degree]

It also has to be planar which means it has to be flat.

PS. I don't think cyclopentene is aromatic because it does not meet the Huckel rule. I think this one has 4 pi electrons so using the Huckel rule 4n+2=4, n=1/2

Thanks for the reply!

However, cyclopentene only has 1 double bond so wouldn't that make it have 2 pi electrons (assuming 1 double bond has 2 pi electrons)? 4(0)+2=2

The study guide I have says it is aromatic so I am confused

 

[delano2000]

Thanks for the reply!

However, cyclopentene only has 1 double bond so wouldn't that make it have 2 pi electrons (assuming 1 double bond has 2 pi electrons)? 4(0)+2=2

The study guide I have says it is aromatic so I am confused

You're right. When I drew the structure somehow I was thinking of cyclopentadiene.

Per Huckel's Rule it would be aromatic because n=0. I think it's also planar because of the geometry of the bond angles being around 120 degrees. Will look into it a bit further.


PS. Thanks for catching my error. That was a test hehe. Jk

 

[Degree]

Wow you guys are awesome! Thanks for answering my question so quickly!

Does anyone know how one should use the verbal ability part of the Dr.Collins package? Is it worthwhile to memorize all the terms?

 

[CutaneousRabbit]

Yes that makes sense, thank you very much!

One last question, is Huckel's rule the only criterion needed to determine if a compound is aromatic or must the compound also satisfy other requirements? What does a 'planar' molecule mean?

Is cyclopentene aromatic?

The other important thing about aromaticity is that all atoms in the ring must be sp2 hybridized.

 

[phathead]

Benzene has 6 pi electrons - 3 pi bonds - pretty much everywhere you have written pi bonds you should have written pi electrons.

sigh, that's what happens when you type that late at night lol