Alkenes

Question 1

Alkenes (7)

Answer 1

Unsaturated
C=C (1 weaker pie, less overlap breaks first, 1 sigma, stronger, more overlap)
More reactive than alkanes
Volatile/flammable
Don’t have max no. Hs
High e density
120* between atoms

Question 2

Alkenes physical properties (3)

Answer 2

Water insoluble
- not enough energy to break C=C
Increase C chain length, increase mp/bp
- increase e density/no. E
- increase Lf strength
- increase ETO
Not used as fuels
- Reactivity for other things
- sootier combustion

Question 3

Alkene isomers

Answer 3

Structural
- positional, move C=C
- chain, branch off HC
- functional, diff functional group (cycloalkanes)
Stereo
- E/Z, higher e density, pie bond, restrict rotation

Question 4

Electrophile

Answer 4

Electron pair acceptor
2 electrons in pie bond
Positive ion or delta + atom

Question 5

Hydrogenation procedure

Answer 5

Addition reaction
Unsaturated C=C —> sat c-c
Alkene + hydrogen —> alkane

Question 6

Hydrogenation conditions

Answer 6

150*C
Nickel catalyst

Question 7

Hydrogenation uses

Answer 7

Margarine
Decrease no C=C, increase mp, veg oil solid at rtp

Question 8

Oxidation procedure

Answer 8

Addition reaction
Alkene —> diol
Shake with acidified (sulfuric acid) potassium manganate
Purple —> colourless
Used to detect alkenes

Question 9

Hydration procedure

Answer 9

Addition reaction
Alkene + steam —> alcohol

Question 10

Hydration conditions

Answer 10

300*c
Phosphoric acid
60/70atm

Question 11

Hydration uses

Answer 11

Bioethanol
Disinfectant

Question 12

Halogen/bromine addition procedure

Answer 12

Alkene + halogen —> dihaloalkane
Orange —> colourless (bromine)
Shaken
Halogen adds across C=C
Increase no. C=C, increase decolorisation speed,
1 atom = electrophile
1 atom = nucleophile
2 step procedure

Question 13

Hydrogen halide addition reaction

Answer 13

HCl/HBr/HI
Add across C=C
Alkene —> haloalkane
Heterolytic fission (both es to halogen)
Can use IBr, ClBr
2 step procedure

Question 14

Unsymmetrical alkenes addition reaction

Answer 14

2 possible products
H-Br bond to either c in C=C
Major/minor product
Mixture of products
Alkyl real ease Es
- positive inducing effect
- stabilises positive of intermediate carbocation
more alkyl groups, more stable carbocation
- tertiary, most stable, most likely, major
- sec/prim, less stable, less likely, minor

Question 15

Concentrated sulfuric acid addition reaction

Answer 15

Like halogens/hydrogen halides
Adds across C=C
H delta + = electrophile
OSO2OH delta - = nucleophile
2 step procedure

Question 16

Conc sulfuric acid addition reaction product handling

Answer 16

Add water —> alcohol + sulfuric acid
Add water across C=C (hydration)
Sulfuric acid, catalyst, regenerated
Hydrolysis, reaction molecule split by water regeneration

Question 17

Polymerisation addition

Answer 17

Monomers bond to form long chain molecule
C=C opens up
Cs can bind to others
Many alkenes —> polymer + no other product

Question 18

Polymer

Answer 18

Huge molecule made of many, small monomers bonded together
RFM < 1 mill

Question 19

Repeat unit

Answer 19

Smallest group of atoms, produce polymer when repeated
Different monomer —> polymer with different physical properties