2. Click here for ethene sigma and pi bond photoshere

3. Bonds are regions of high electron density pi bonds are exposed and are therefore more vulnerable to attack by electrophiles.

6. Click here for mechanismhere

7. Evidence for the mechanism. If HBr is used in the presence of NaCl the products are: MAIN PRODUCTSMINOR PRODUCTS CH 3 CHBrCH 3 CH 3 CH 2 CH 2 Br CH 3 CHClCH 3 CH 3 CH 2 CH 2 Cl

8. Hydrogenation Hydrogenation is the addition of hydrogen across a double bond. This results in an unsaturated bond.  1 mole of H 2 reacts with 1 mole of double bond.  Usually a catalyst (eg nickel) is used.

9. Alkenes with acidified potassium manganate (VII) This is an oxidation reaction - OH group adds across the double bond - a diol forms - solution turns colourless (from purple) - alternative test for a C=C bond [O] KMnO 4 / H + ethan-1,2-diol

10. Exam Questions

12. Click here to look at isomerism in alkenes