Which carbon(s) in cyclohexene have the highest electron density?

[![enter image description here](https://i.stack.imgur.com/Pap9m.jpg)](https://i.stack.imgur.com/Pap9m.jpg)


I think that carbons with highest electron density will be both $\ce C1$ and $\ce C2$ because of the loosely held $\pi$-bond between them, but according to the answer given the carbons with most electron density should be both $\ce C3$ and $\ce C6$.


How is this possible?




:-( The book gives an answer, not necessarily the right one.


Looking at the [$\ce{^13C}$ NMR of cyclohexene](http://www.chemicalbook.com/SpectrumEN_110-83-8_13CNMR.htm) the carbons at positions 4 and 5, in your diagram, are shifted the least and therefore have the most shielding. Thus those carbon atoms also have the greatest electron density around them. 


 4

Intuitively, I would expect carbons 1/2 to have the highest electron density. MaxW's NMR spectrum does indeed suggest that 1/2 have the *least* density, then 3/6, with carbons 4/5 being the most electron-dense. 


I suppose you could rationalize this conclusion by saying the the CH2 carbons (3/6, 4/5) will suck a bit of density from the attached hydrogens (because C is slightly more electronegative than H), whereas carbons 1/2 only have one H each to pull electron density from, therefore 1/2 have the least electron density. But my gut feels uncomfortable about this. 


I attempted to calculate an electrostatic potential map of cyclohexene, but unfortunately I'm not proficient with the software. I think that's what we need here though.


For what's worth, here is a computer-generated model showing that there is more *current density* around the carbons you labeled 1/2: 


[![enter image description here](https://i.stack.imgur.com/vPTiF.jpg)](https://i.stack.imgur.com/vPTiF.jpg)
(<http://pubs.rsc.org/en/content/articlelanding/2012/cs/c2cs35037h>)


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