Bonding
The type of bonding can be explained in terms of orbital hybridization. In ethylene each carbon atom has three sp2 orbitals and one p-orbital. The three sp2 orbitals lie in a plane with 120° angles. The p-orbital is perpendicular to this plane. When the carbon atoms approach each other, two of the sp2 orbitals overlap to form a sigma bond. At the same time, the two p-orbitals approach (again in the same plane) and together they form a pi-bond. For maximum overlap, the p-orbitals have to remain parallel, and, therefore, rotation around the central bond is not possible. This property gives rise to cis-trans isomerism. Double bonds are shorter than single bonds because p-orbital overlap is maximized.
| 2 sp2 orbitals (total of 3 such orbitals) approach to form a sp2-sp2 sigma bond | Two p-orbitals overlap to form a pi-bond in a plane parallel to the sigma plane |
With 133 pm, the C=C bond length is shorter than the C−C length in ethane with 154 pm. The double bond is also stronger, 636 (KJ/mol) versus 368 kJ/mole but not twice as much as the pi-bond is weaker than the sigma bond due to less effective pi-overlap.
In an alternative representation, the double bond results from two overlapping sp3 orbitals as in a bent bond.
Read more about this topic: Double Bond
Famous quotes containing the word bonding:
“The bottom line on bonding with multiples seems to be that if you see bonding as a static event—a moment in time at which you must have eye contact and skin contact simultaneously with two or more infants—you may indeed be in trouble.”
—Pamela Patrick Novotny (20th century)
“At the heart of male bonding is this experience of boys in early puberty: they know they must break free from their mothers and the civilized world of women, but they are not ready yet for the world of men, so they are only at home with other boys, equally outcast, equally frightened, and equally involved in posturing what they believe to be manhood.”
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“Attachment to a baby is a long-term process, not a single, magical moment. The opportunity for bonding at birth may be compared to falling in love—staying in love takes longer and demands more work.”
—T. Berry Brazelton (20th century)