6C - Alkenes

Question 1

whats the general formula of an alkene ? 1

Answer 1

• CnH2n

Question 2

what is the bonding in alkenes ? 1

Answer 2

• pi and sigma bonds

Question 3

what’s an electrophile ? 1

Answer 3

• electron loving ; electron pair acceptors

- positive charge

Question 4

Alkene + H2

• catalyst ?temp ?
• mechanism
• example
• 3

Answer 4

• produces an Alkane
• Nickel catalyst at 150c
• electophilic addition
• makes Margarine by catalytic hydrogenation of unsaturated vegetable oils

Question 5

whats electrophilic addition ? 3

Answer 5

• alkene double bonds open up
• atoms added to the carbon atom
• double bond attracts electrophiles

Question 6

Alkene+ Halogen ? 6
- produces ?
-mechanism ?
-outline 
example

Answer 6

• Produces dihalogenoalkanes = electrophilic addition
• double bond repels electrons in Br-Br=polarises it
• HETEROLYTIC FISSION closest Br binds to alkene
• Positively charged CARBOCATION
• Br- zooms over and the dihalogenoalkane is made
• Bromine water = orange to colourless as the Br is added to the C=C bond .

Question 7

Alkenes + hydrogen halides ?

2

Answer 7

• electrophilic addition

- forms HALOGENOALKANE

Question 8

What happens if you add Hydrogen halides to unsymmetrical halogenoalkanes ?
-Markowinikoff’s rule
6

Answer 8

• 2 products formed
• amount of each depends on stability of carbocation ]
• tertiary

Question 9

Alkenes + steam 3

Answer 9

• hydrated by steam at 300c
• Phosporic Acid Catalyst
• makes ethanol from ethene

Question 10

Alkene + acidified potassium Manganate? 3

Answer 10

• acid conditions
• oxidise alkene to make DIOL
• purple –> colourless

Question 11

What does heterolytic bond fission of covalent bond produce ? 1

Answer 11

-ions

Question 12

how do alkenes produce polymers ? 1

Answer 12

• addition polymerisation