4.1.3- Alkenes

Question 1

What is the double bond in an alkene?

Answer 1

An area of high electron density, making it susceptible to attack from electrophiles

Question 2

What does the double bond consist of?

Answer 2

A pi bond and a sigma bond

Question 3

What is a pi bond?

Answer 3

A sideways overlap of adjacent p-orbitals above or below the bonding C atoms

Question 4

What is a sigma bond?

Answer 4

Formed by the overlap of orbitals directly between the bonding atoms

Question 5

What shape are alkenes?

Answer 5

Trifocals planar

Question 6

What is the test for alkenes?

Answer 6

Bromine water turns from orange-brown to colourless because the bromine forms bonds to the carbon atoms, removing the double bond

Question 7

What is stereoisomerism?

Answer 7

Compounds with the same structural formula but a different arrangement of atoms in space

Question 8

What is E isomerism?

Answer 8

Opposite sides

Question 9

What is Z isomerism?

Answer 9

Same side

Question 10

What are the priority rules for stereoisomerism?

Answer 10

The atom on each side of the double bond with the higher Ar or Mr is given the highest priority

Question 11

How are alkanes produced from alkenes?

Answer 11

Alkenes undergo electrophilic addition with hydrogen

Question 12

What does the reaction of alkenes and hydrogen to produce alkanes require?

Answer 12

A nickel catalyst

Question 13

How are haloalkanes produced from alkenes?

Answer 13

Alkenes undergo addition reactions with halogens to form disubstituted haloalkenes, and with hydrogen halides to form mono-substituted haloalkenes

Question 14

How are alcohols produced from alkenes?

Answer 14

Alkenes undergo addition reactions with steam to form alcohols

Question 15

What does the reaction of alkenes with steam to make alcohols require?

Answer 15

An acid catalyst

Question 16

What is an electrophile?

Answer 16

An electron pair acceptor and are attracted to areas of high electron density

Question 17

What is electrophilic addition?

Answer 17

The reaction mechanism that shows how electrophiles attack the double bond in alkenes

Question 18

What is formed when a double bond is broken?

Answer 18

A carbocation intermediate

Question 19

What is the most and least stable carbocation?

Answer 19

Tertiary is the most and primary is the least

Question 20

What is markownikoff’s rule?

Answer 20

The hydrogen joins the carbon atom which is bonded to the most hydrogen atoms. The bromide ion bonds to the carbon atom which is joined to the most carbon atoms

Question 21

What are addition polymers formed from?

Answer 21

Alkenes which are short chain monomers

Question 22

What are the benefits of using cheap oil deprived plastics counteracted by?

Answer 22

Problems for the environment if they go to landfill

Question 23

How are polymers disposed?

Answer 23

-recycled
-used as organic feedstock to produce other organic chemicals and plastics
-combusted to produce energy

Question 24

What does the combustion release?

Answer 24

Toxic gases