Why is a C=N double bond shorter than a C=C double bond?

1 Answer
Jun 4, 2015

Nitrogen has a smaller atomic radius from the periodic table trend of increased Zeff from left to right, so the internuclear distance in a C=N bond for optimal orbital overlap is closer than for a C=C bond.

The optimal internuclear distance is shown in a potential energy curve similar to this one:

http://l.yimg.com/http://l.yimg.com/