alkenes

Question 1

what is an alkene

Answer 1

unsaturated hydrocarbons with a C=C double bond

Question 2

what is the general formula of an alkene

Answer 2

CnH2n

Question 3

why no rotation about the C=C double bond

Answer 3

due to pi orbital - electron density above and below the single bond, which holds the carbon atoms in place

Question 4

are alkenes more or less reactive than alkanes

Answer 4

more reactive, due to high electron density of double bond and the fact the pi-bond is slightly easier to break

Question 5

what intermolecular forces of attraction do alkenes have

Answer 5

only van der waals due to non-polar bonds

Question 6

are alkenes soluble in water

Answer 6

no

Question 7

3 kinds of isomerism alkenes can have

Answer 7

chain isomers
position isomers
geometric E-Z isomers

Question 8

what is an electrophile

Answer 8

electron deficient atoms/ions which accept a pair of electrons

Question 9

what is the most stable kind of carbocation intermediate

Answer 9

alkyl groups have a positive inductive effect, so the most stable carbocation is the one bonded to the most other carbon atoms

Question 10

major products will be formed from which kinds of carbocations

Answer 10

tertiary

Question 11

what conditions are needed for the electrophilic addition of H2O to an alkene

Answer 11

acid catalyst, usually phosphoric acid

Question 12

what are the products of the reaction

Answer 12

an alcohol

Question 13

what conditions are needed for the electrophilic addition of a hydrogen halide to an alkene

Answer 13

room temperature

Question 14

what conditions are needed for the electrophilic addition of a halogen molecule to an alkene

Answer 14

room temp and an organic solvent

Question 15

how does a molecule with a non-polar bond react as if it is an electrophile

Answer 15

C=C double bond with a high electron density induces a temporary dipole in the halogen molecule –> delta positive atom attracted to double bond

Question 16

how would you turn the product into an alcohol and how does show that sulfuric acid catalyses the addition of water to an alkene

Answer 16

add water

H2SO4 reforms, showing it catalyses the hydration of alkenes

Question 17

what is an addition polymer

Answer 17

many monomers bonded together via rearrangement of bonds without the loss of any atom or molecules

Question 18

what are monomers and what form do they usually take

Answer 18

molecules which combine to form a polymer

usually have a C=C bond which breaks to leave a repeating pattern

Question 19

give 3 uses of poly(cholorethene)

(PVC)

Answer 19

drainpipes
vinyl
aprons

Question 20

give two examples of plasticisers

Answer 20

esters
phthalates

Question 21

what are plasticisers

Answer 21

small molecules that get between polymer chains to force them apart and allow them to slide over one another

Question 22

how do the physical properties of PVC change due to a plasticiser

Answer 22

PVC with plasticiser become flexible, used for aprons

without, it is rigid and used for drainpipes

Question 23

why do things containing mainly C-C and C-H bonds not decompose easily

Answer 23

bonds are non-polar so are not attacked by enzymes

Question 24

why is a lack of biodegrabability in compounds with C-C or C-H bonds a problem

Answer 24

disposal is problematic

Question 25

what is mechanical recycling

Answer 25

where plastics are separated into different types, washed, ground down, melted and re-moulded

Question 26

what is mechanical recycling used for

Answer 26

soft drinks bottles –> fleeces

Question 27

what is feedstock recycling

Answer 27

plastics heated to a temperature which break polymer bonds, leaving original monomers that can be made into new plastics

Question 28

what is feedstock recycling used for

Answer 28

making totally new plastics

Question 29

what is a problem with recycling

Answer 29

each time thermosoftening plastics are melted and remoulded, their properties degrade, so they can only be remoulded a limited number of times