wierd ORGO Q

[flycd05]

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The orientation of the bond between the two sp2 hybridized carbons in the molecule ethene can be best described as ________ in relation to the orientation of its pi bond:

a - parallel
b - perpendicular
c - at a 109.5 angle
d - at 120 angle
e - at 180 angle

I picked D (120 angle b/c sp2 is 120 degrees) but the correct answer is A. Can someone explain this or is this an error in Barron's??

 

[Maygyver]

I would assume a pi bond connects the two orbitals so it will be parallel..I think. It's hard for me to explain.

 

[boxdesker]

This picture:

http://www.chem1.com/acad/webtext/chembond/CB-images/dblbond-PH.gif

on this website:

http://www.chem1.com/acad/webtext/chembond/cb07.html

...explains it.

My first guess was perpendicular, but the correct answer is parallel.

 

[flycd05]

This picture:

http://www.chem1.com/acad/webtext/chembond/CB-images/dblbond-PH.gif

on this website:

http://www.chem1.com/acad/webtext/chembond/cb07.html

...explains it.

My first guess was perpendicular, but the correct answer is parallel.

"Since sp2 hybrid orbitals are always in the same plane, the entire ethylene molecule is planar. However, there remains on each carbon atom an electron in an unhybridized atomic pz orbital that is perpendicular to the molecular plane. These two parallel pz orbitals will interact with each other; the two orbitals merge, forming a sausage-like charge cloud (the π bond) that extends both above and belowthe plane of the molecule."

according to this, it should be perpendicular not parallel. someone correct me if im wrong pleaseeee.

 

[wifi08]

120 degrees is the correct answer for the distance between each substituent. but that is not the correct answer. what the question wants to know is how the double bond i.e. Pi orbital interacts with the other Pi orbital that its sharing electrons with.
for this you have to know that the Pi orbital is like an 8 with its center touching the ring and electrons are shred with the other pi orbital with whom it is parellel to. then between the two electrons are shared above and below the molecule.
i hope i did a good job explaining its best to see a picture