3.3.4.1 Structure, bonding and reactivity

Question 1

What are alkenes?

Answer 1

Unsaturated hydrocarbons
Bonding in alkenes involves a double covalent bond, a
centre of high electron density

Question 2

What is the structure of electron density in a double covalent bond?

Answer 2

Overlapping s orbitals form a strong bond due to the electron density between the protons
Weaker p orbitals lie above or below the s bond, called a pi bond, area of negativity around it makes it more reactive, electron density is easily accessible

Question 3

What are the properties of alkenes?

Answer 3

Contain at least one carbon to carbon double bond
Unsaturated
Have isomers because the double bond can be in different places
Rotation is allowed around the single bonds
Reactive compounds
Don’t burn cleanly
Decolourise bromine water
Chain length increases as: boiling point increases, viscosity increases, volatility decreases

Question 4

What are E and Z isomers?

Answer 4

Of the four groups around a double bond, count up the atomic number
If the highest groups are on the same side, the isomer is Z
If the highest groups are on different sides, the isomer is E

Question 5

What is the structure of the double carbon bond?

Answer 5

Sigma bond between the nuclei

Pi bond above the sigma bond which is weaker