Properties Of Alkenes

Question 1

What is an alkene?

Answer 1

An unsaturated hydrogen carbon wit at least one C=C double bond

Question 2

Describe the bonding in alkenes.

Answer 2

1. Each carbon atoms has 4 electrons which can be used to form bonds
2. For carbon atoms in the double bond:

• 3/4 electrons are used in three sigma bonds
  —> one to the other carbon and two to other atoms
• the fourth electron is in a pi bond
  —> sideways p orbitals overlap above and below the plane of the carbon atoms
  —> each carbon atoms supplies one electron to the pair in the pi bond
  —> the pi electron density is above and below the plane of the carbon atoms
  —> bond is non-rotational as pi bond locks in place

Question 3

What is the shape around a double bond?

Answer 3

Trigonal planar

• 3 regions of electron density repel each other as far apart as possible
• 120 degrees