4.1.3 alkenes

Question 1

what is a sigma bond

Answer 1

when 2 s-orbitals directly overlap

Question 2

what is a pi bond

Answer 2

sideways overlap of two p orbitals

Question 3

draw diagram

Answer 3

in booklet

Question 4

what is the bond angle in alkene

Answer 4

120 as there are 3 bonding regions of electrons which repel one another equally

Question 5

what is a structural isomer

Answer 5

same molecular formula but different structural formula

Question 6

what is stereoisomerism

Answer 6

same structural formula but different arrangements of atoms in space

Question 7

what must a compound have for it to have E/Z isomerism
(type of stereoisomerism)

Answer 7

-a c=c double bond
-each carbon must have two different groups attached to it

Question 8

e isomer

Answer 8

high priority groups are on the opposite side

Question 9

z isomer

Answer 9

high priority groups are on the same side

Question 10

cis/trans

Answer 10

each carbon has one of the same groups

Question 11

cis

Answer 11

same group is on the same side

Question 12

trans

Answer 12

same group is on the opposite sides

Question 13

are alkenes or alkanes more reactive

Answer 13

alkenes as the pi bond has a lower bond enthalpy than the sigma bond

Question 14

alkene to alkane

Answer 14

add H2
-nickel catalyst, 150 degrees

Question 15

alkene to haloalkane

Answer 15

-add hydrogen halide
-NOTE- if alkene is unsymmetrical two products are possible

Question 16

alkene to alcohol

Answer 16

-Add H2O (steam)
-phosphoric acid catalyst, 60 atm, 300 degrees

Question 17

testing for alkene

Answer 17

add bromine water
-decolourises from orange to colourless

Question 18

electrophile

Answer 18

electron pair acceptor

Question 19

heterolytic fission

Answer 19

breaking of a covalent bond so both electrons from the bond go to one atom

Question 20

curly arrows

Answer 20

show the movement of electron pairs

Question 21

what is the mechanism for an alkene called

Answer 21

electrophilic addition

Question 22

which carbocation is more stable and what does this mean about the amount of product formed

Answer 22

secondary carbocation intermediate is more stable than a primary carbocation intermediate
so more product is formed from a secondary carbocation intermediate

Question 23

how do simple monomer alkenes join together

Answer 23

simple monomer alkenes join together to form long chain polymers
the pi bond breaks to form new sigma bonds

Question 24

conditions for addition polymerisation

Answer 24

high pressure and a catalyst

Question 25

draw the general equation for polymerisation

Answer 25

in booklet

Question 26

how to name a polymer

Answer 26

poly(alkene)

Question 27

What are three ways to dispose of plastics

Answer 27

Recycle them use them as organic feedstock Combust them to generate electricity

Question 28

processing of waste polymers (energy production)

Answer 28

some polymers are difficult to recycle so they can be burnt to produce heat energy which can be harnessed to produce electricity

Question 29

processing of waste polymers (removal of toxic waste product)

Answer 29

when plastics are burnt to make electricity they produce the toxic by-product HCL if waste products are processed to remove the PVC this problem can be avoided. Solvents have been developed to dissolve the PVC

Question 30

how can polymers be processed in a sustainable way

Answer 30

use as organic feedstock

Question 31

how do you remove HCL

Answer 31

react with an alkali/base eg-naOH

Question 32

what is a biodegradable polymer

Answer 32

can be broken down naturally in the environment by microorganisms

Question 33

what is a photodegradable polymer

Answer 33

can be broken down naturally over time by absorbing light