13.1 The Properties Of Alkenes

Question 1

What is a sigma bond?

Answer 1

A bind caused by orbital overlap directly between the bonding atoms

Question 2

What is a pi bond?

Answer 2

A bond caused by sideways overlap of adjacent p orbitals above and below the bonding atoms

Question 3

What us the general formula of an alkene?

Answer 3

CnH2n

Question 4

Why can’t the C=C bond rotate?

Answer 4

Because of the pi bond

Question 5

What is the shape around the C=C bond and why?

Answer 5

There are three regions of electron density around each carbon atom in the C=C bond
The three regions of electron density repel each other as far as possible
This creates a trigonal planar shape
With bond angles of 120°

Question 6

Which is more reactive: alkanes or alkenes?

Answer 6

Alkenes

Question 7

How does the pi bond effect the alkenes reactivity?

Answer 7

The pi bond introduced a region of high electron density above and below the plane of the bonding C atoms in the C=C bond
Electron-deficient species called electrophiles can attack the high electron density of the pi bond, causing the alkene to react
In the C=C bond, the pi bond has a smaller bond enthalpy than the sigma bond and is broken more easily