Reactions of Alkenes

Question 1

What is electrophillic addition?

Answer 1

The double bonds open up and atoms are added to the carbon atoms.

Question 2

What are electrophiles?

Answer 2

Electron pair acceptors- they’re usually a bit short of electrons, so they’re attracted to areas where there’s lots of them about.

Question 3

What does adding hydrogen to C=C bonds produce?

Answer 3

Alkanes.

Question 4

Ethene will react with hydrogen gas to produce ethane under what conditions?

Answer 4

With a nickel catalyst at a temperature of 150 degrees C.

Question 5

How can you test for C=C double bonds?

Answer 5

With bromine water.

Question 6

What is the electrophillic addition mechanism for using bromine water to test for C=C double bonds?

Answer 6

The double bond repels the electrons in Br2, polarising Br-Br.
Heterolytic (unequal) fission of Br2. The closer Br gives up the bonding electrons to the other Br and sticks to the C atom.
You get a positively charged carbocation intermediate. The Br- moves and bonds to the other C atom.