N&PD Moderators: Skorpio
Double bounds on a ring
Lucid Dream
Bluelighter
lets take the benzene ring, why do the double bonds not pull those to carbons into each other. Shouldn't there be a difference in distance? I'm my reading it's trying to explain how the electrons move freely amoungst the ring, but I'm still very iffy on this. If anyone thinks they can extract my question from this mess of words, please help.
amapola
Bluelight Crew
Question: "What the fuck is up with benzene?"
Answer: Chemists don't know shit.
Stick with the non-localized theory where electrons are in two places at once and draw it like this.
In effect there are no single bonds, and no double bonds, just an equal number of 3/2 bonds.
Lucid Dream
Bluelighter
Wow, okay. I like this explanation, but my only problem is my book says different LOL. Thanks for bringing this to my attention. Its funny to think that we can make drugs that have direct effects on different functions of the body, and all kinds of really neat shit, but I can't get a 100% straight answer on the benzene ring LOL. Just goes to show how much we don't know.
Thanks.
Lucid Dream
Bluelighter
In MO theory this is a direct consequence of the fact that the 3 molecular pi orbitals form a combination which evenly spreads the extra 6 electrons over 6 carbon atoms.
Seems to be a lot of theories out there. Makes this hard for me to choose. I have a feeling I'm going to be confused a lot for the next 5 years 
amapola
Bluelight Crew
I see you are in orgo so I'll expand by saying remember that each covalent bonds has 2 electrons. Therefore between any two carbons you do get a solid sigma bond and it is only the pi bond which is a half bond.
tryp2fun
Bluelighter
We know plenty. The structure of benzene has been determined very precisely, and its properties can be calculated with great precision. You are just seeing a limitation in the way that we can represent molecular structures in a simple drawing. This is an old problem that was solved by Kekule and Loschmidt in the 1860's.
Chauncey_GARDENer
Bluelighter
Yes, in 1865, the German organic chemist Freidrich August Kekule von Stradonitz proposed the 6 membered ring structure of benzene. Chemists had known the empirical formula to benzene, however, the high degree of un-saturation remained a mystery until Kekule's proposition.
The funny thing is how Kekule came about this discovery. He told people that the structure had come to him in a vision, a vision of a snake devouring its own tail, encircling itself infinitely. This snake vision accounts for the delocalized ring of electrons.
Better yet, an old chemistry professor of mine claimed that Kekule's vision was a byproduct of a mescaline induced psychedelic experience. However, I have yet to find any evidence to back up this claim, and I've looked all over the internet.
Astavats
Bluelighter
Mescaline wouldn't be extracted for another three decades but if your professor meant peyote that would be possible.
Edit: Isolated not extracted.
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dread
Bluelighter
IMO benzene is the most beautiful chemical structure in existence. It's so clean and symmetric, simple, yet it just seems to make sense on some weird metaphysical level.
They do. Bond length for alkanes is 1.54 angstroms. For benzene, it is 1.39 angstroms. This is not theory. This has been measured.
amapola
Bluelight Crew
^The OP originally thought there were 3 double bonds and 3 single and the double bonds would be shorter than the singles.
I feel the same way about butanal. I mean but*anal* it's like metametaphysical weird.
