Help with o-chem structures?

Question

The question is to draw a line-bond structure for propene, CH3CH=CH2, and indicate the hybridization of each carbon and predict the value of each bond angle. I figured out how to draw the lines and how it is arranged, but I don't know why there is a bend in the structure. Why does it bend? Does it have something to do with the hybridization? How do you predict this?

Answer 1

CH3: The hybridization of C is sp3, and the bond angles are 107deg, including the H-C-C angle, oriented toward the apexes of a tetrahedron.

First -CH=: The hybridization is sp2. The bond angles C-C=, C-C-H, and C(H)C= are each 120deg. This is the reason for the bend in the H3C-C= bend.

Final =CH2: Hybridization sp2. Bond angles C=C-H all 120deg.

Answer 2

The C=C bond in propene is a sigma-pi bond, where the orbitals are sp2 hybridized so the bond angles are about 120 degrees. the C of the CH3 is a normal sp3 hybrid where the bond angles will be around 109.5 degrees (there may be a bit of distrortion due to steric constraints with the larger -CH=CH2 group attached to one hybrid orbital).

A really good explanation can be found at:

http://www.mhhe.com/physsci/chemistry/carey5e/Ch02/ch2-3-2.html

Hope this helps and mail me if you need anything else.