Achiever 3 Ochem 72

[sl2obel2ts]

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N in pyridine aromatic molecule, which N donates 2 electrons to complete aromacity, why is N not SP2 configuration?

I would expect 2 electrons participate in aromacity and yield Sp2.



and 99 is also really weird.
If you chlorinate using hv on (ch3)2ch2ch2ch3 I would expect it to attack 1' as kaplan says.
"chlorination is more rapid process and thus depends not only on the stability of intermediate, but on the number of hydrogen present, likely replace primary hydrogens because of their abundance."

 

[sl2obel2ts]

anyone?

 

[ET87]

in pyridine, while i suppose that it's lone pair is free to hang out with the aromatic electrons, i do believe that it typically sticks out in sp2 fashion out of the ring and it more provides One of it's other electrons in a similar way that the carbons provide One of their electrons towards the ring to complete aromaticity.

 

[TeamGuo]

N lone pair in pyridine does not participate in aromaticity.

If you work out the resonance, since N is much more electronegative than C, lone pairs from the ring donates to the N.

If you have the lone pair from N in the ring, that would make the pyridine ring anti-aromatic.

I want to answer your second question but I don't have achiever and not sure what you started out with.

Your chemical formula is slightly off I think, you have an extra H.

 

[sl2obel2ts]

actually i think the question is wrong it is not actually pyridine. Check this out. The problem said this molecule

(supposeldy pyridine but NOT) does NOT have SP2 configuration. I just dont understand. In order to complete aromacity, it should donate 2 electrons and stabilize the ring.

 

[TeamGuo]

actually i think the question is wrong it is not actually pyridine. Check this out. The problem said this molecule

(supposeldy pyridine but NOT) does NOT have SP2 configuration. I just dont understand. In order to complete aromacity, it should donate 2 electrons and stabilize the ring.

Oh ok, this makes more sense. Pyridine N actually has sp2 hybridization.

This molecule is called pyrrole, and the lone pair actually participates in aromaticity. N is sp3 hybridized not sp2 though. There are 4 things around the N atom, which is the easiest way to find hybridization.

N on pyridine has 3 "things" around itself, pyrrole N has 3 bonds and 1 LP electrons = sp3.

Hope that helped.

 

[sl2obel2ts]

so even if two lone pair electrons participate in aromacity, it is still not hybridized to sp2. didnt know that.

hey what about question 99?

 

[TeamGuo]

What's the actual question on 99?

It started out as an alkene?

 

[sl2obel2ts]

and 99 is also really weird.
If you chlorinate using hv on (ch3)2ch2ch2ch3 I would expect it to attack 1' as kaplan says.
"chlorination is more rapid process and thus depends not only on the stability of intermediate, but on the number of hydrogen present, likely replace primary hydrogens because of their abundance."

started as alkane. basically asking for which carbon will cl attach to. Achiever says 3', which I disagree.