12.2 Alkenes (What are Alkenes?)

Question 1

What does the double bond in an alkene imply?

Answer 1

That alkenes are unsaturated hydrocarbons.

Question 2

Double Bond

Answer 2

4 electrons in the double bond
Region between the two carbon atoms a higher than normal density of negative charge.
Positive ions or molecules with a partial positive charge on the atoms, will be attracted to this negative region and accept a pair of electrons.
Bond angles around the C=C double bond is 120 (Two single bonds and one double bond, 3 groups).

Question 3

What is an Electrophile?

Answer 3

An electrophile is a positive ion or molecule with a partial positive charge that will be attracted to a negatively charged region and react by accepting a lone pair of electrons to form a covalent bond.

Question 4

Electrophilic Addition Reactions

Answer 4

1. Bromine
2. Bromine (aq)
3. Hydrogen Bromide
4. Water
5. Hydrogen

Question 5

Test for unsaturation

Answer 5

Bubble alkene (ethane) gas through bromine the red-brown bromine becomes decolorised.

Question 6

What is an Addition Reaction?

Answer 6

Where two or more molecules react to form a single larger molecule.