Alkenes

Question 1

What are Alkenes ?

Answer 1

• unsaturated hydrocarbons
• general formular CnH2n
• they can be branched, contain more than one double bond, or cyclic

Question 2

Define unsaturated hydrocarbon

Answer 2

• contain a multiple carbon to carbon bond

- so does not contain the maximum number of hydrogen atom

Question 3

Describe what a C=C bond contains

Answer 3

• one sigma bond

- one pi bond

Question 4

How is a sigma bond formed ?

Answer 4

• two sp^2 orbitals overlap

Question 5

How are pi bond formed ?

Answer 5

• the sideways overlap of two p orbitals on each carbon atom

- forming a pi bond above and below the plane of the molecule

Question 6

Where is the electron density in pi bond concentrated?

Answer 6

• above and below the sigma bond joining the nuclei of the bonding atoms

Question 7

Which bond is stronger ?

Answer 7

• sigma bonds as there is more overlap of orbital paths

Question 8

What do pi bond prevent ?

Answer 8

• rotation about the double bond

- as it locks the two carbon atoms in a fixed position

Question 9

What is the shape around each carbon tom involved in the double bond ?

Answer 9

TRIGONAL PLANAR

• three regions of electron density around each carbon atom
• the three regions repel each other as far as possible
• so has a bond angle of 120