Alkenes (Bonding and shape)

Why are alkenes considered unsaturated?

Because they contain a C=C double bond

Which two types of bond does the C=C bond consist of?

A pi bond and a sigma bond

How is a sigma bond formed?

By the direct/end to end overlap of orbitals between the bonding atoms

How are pi bonds formed?

By the sideways overlap of adjacent p-orbitals above and below the C atoms

How many sigma bonds are made by each carbon of the C=C?

3

Where is the pi electron density concentrated in an alkene molecule?

Above or below the plane of carbon atoms

How many pi bonds are in alkenes and why?

1 because there’s only one pair of electrons involved (can be above or below the plane)

How many electron regions are around the double-bonded carbon atoms in alkenes?

3 electron regions in the double-bonded carbon atoms (the double bond counts as 1 electron region)

What is the electron repulsion like in alkenes and why?

• Equal repulsion of electrons

• Because it is composed of bonding regions only (there are no lone pairs)

Name the shape and bonding angle of the C=C region in an alkene

Trigonal planar, 120 degree bonding angle

How many electron regions are around the single-bonded carbon atoms in alkenes?

4 electron regions (one bond is a region basically)

Name the shape and bonding angle of the C-C bond in alkenes.

Tetrahedral, 109.5 degree bond angle

Why does the strength of the bond increase as the amount of bond increases? (i.e. single<double<triple)

This is due to the increased electron density around the carbon-carbon bond, making the bond stronger and more difficult to break.