Alkenes

Question 1

General formula

Answer 1

CnH2n

Question 2

Saturated or unsaturated?

Answer 2

Unsaturated - contain a C=C bond

Question 3

What does the double bond consist of?

Answer 3

Sigma σ and Pi covalent bonds.

Question 4

Which of the two bonds is stronger?

Answer 4

σ - sigma bonds are stronger than Pi bonds. The C=C is stronger than the C-C.

Question 5

Which is longer?

Answer 5

C=C bond length is shorter than the C-C

Question 6

How are σ bonds formed? And draw them

Answer 6

From the LINEAR overlap of 2 s-orbitals, an s-orbital and a p-orbital and two p-orbitals. All of which result in free rotation along the bond axis.

Question 7

How are Pi bonds formed? and draw them.

Answer 7

The SIDEWAYS overlap of two p-orbitals, this results in restricted rotation along the bond axis.

Question 8

What is the C=C bond a region of?

Answer 8

High electron density, which makes it open to attack from electrophiles.

Question 9

What is more reactive alkanes or alkenes

Answer 9

Alkenes

Question 10

What happens when alkenes undergo addition reactions?

Answer 10

The Pi bond is broken, the addition occurs across the double bond.

Question 11

What are the conditions necessary for the complete combustion of an alkene?

Answer 11

A source of ignition and a plentiful supply of oxygen

Question 12

Write an equation for the combustion of ethene

Answer 12

in book

Question 13

What are the conditions for incomplete combustion?

Answer 13

A source of ignition and a limited supply of oxygen

Question 14

Write an equation

Answer 14

in book

Question 15

What is the name of the mechanism and draw the mechanism of the bromination of ethene.

Answer 15

Electrophilic addition - in book

Question 16

Whats the splitting of HBr representative of?

Answer 16

Heterolytic fission

Question 17

What do alkyl groups do to a carbocation?

Answer 17

They stabilise it, therefore a tertiary carbocation is more stable than a secondary carbocation which is more stable than a primary carbocation.

Question 18

Does this affect the products made in any way

Answer 18

Yes, products that have a tertiary carbocation will be made much more than products which had a secondary etc.

Question 19

What are the conditions and products for the hydrogenation of an alkene.

Answer 19

Conditions - finely divided nickel catalyst, 180ºC and 4atm

Product - an Alkane

Question 20

What are the conditions and products for the hydration of an alkene with steam?

Answer 20

Concentrated phosphoric acid, 300ºC, 60-70atm

Ethanol

Question 21

What are the conditions and products for the bromination of an alkene with bromine water?

Answer 21

Mix bromine water with liquid alkene or bubble the alkene through bromine water
A dibromoalkane

Question 22

How do you test for a C=C bond?

Answer 22

If yellow bromine water changes to colourless the compound contains a C=C bond.

Question 23

Draw the addition polymerisation 3 vinyl chloride molecules to form one polyvinyl chloride molecule via addition polymerisation

Answer 23

in book

Question 24

What happens when you use excess reactant?

Answer 24

All the functional groups react