Component 2, 2.5 Hydrocarbons

Question 1

Alkanes

Answer 1

hydrocarbons containing only
C-H bonds

C-C bonds

sigma bonds σ

Question 2

conbustion of Alkanes

Answer 2

good fuels

release lots of energy when they burn

complete of incomplete combustion

Question 3

fission

Answer 3

breaking of a covalent bond

Question 4

homolytic fission

Answer 4

the pair of electrons is split between the separated atoms

Question 5

hetrolytic fission

Answer 5

the pair of electrons is taken by one of the atoms

Question 6

free radical substitution

Answer 6

Homolytic fission of halogen bond in presence of UV light

produce halogenalkanes

Question 7

What happens to the bonds in free radical substitution

Answer 7

UV light breaks halogen bonds

Producing intermediates (molecules formed during a reaction)

called free radicals

Question 8

what do free radicals do to alkanes

Answer 8

attack alkanes

lead to reactions:

initiation

propagation

termination

Question 9

initiation

Answer 9

halogen broken down with UV light

Question 10

propagation

Answer 10

hydrogen replaced with halogen radical formed

radical acts as a catalyst

Question 11

termination

Answer 11

two radicals joing to end chain reaction

form a stable product

Question 12

propagation extra

Answer 12

can result in multiple substitutions

chain reaction

conditions altered to favour terimnation step

Question 13

alkenes

Answer 13

unsaturated hydrocarbons

carbon carbon double bond

area of high electron density - susceptible to attack from electrophiles

double bond has σ and π

Question 14

bonds in alkenes

Answer 14

Question 15

tests for alkenes

Answer 15

bromine water - orange/brown to colourless forms dibromo-alkane, double bond opens up forms bonds with bromine atoms

potassium maganate (VII) - under acidic conditions purple to colourless, alkaline conditions purple to dark green

Question 16

Stereoisomers

Answer 16

same molecular formula

different spatial arrangement

Question 17

types of stereoisomers

Answer 17

E-isomer - high priority group diagonally across

Z-isomer - high priority group same side

Question 18

carbocations

Answer 18

primary carbocation

secondary carbocation

tertiary cation

reaction proveeds by most stable intermediate

in addition reactions multiple products can form

Question 19

Sigma bond σ

Answer 19

S orbitals overlap

can rotate

no change in molecule

alkanes form only sigma bonds

Question 20

Pie bond π

Answer 20

alkenes

2 pairs of electrons form between carbon atoms (one pair from each of the overlapping orbitals)

can’t rotate, leads to goemetric isomers

Question 21

just hydrocarbons

Answer 21

Hydrogen groups on same side = CIS isomer

Hydrogen groups on opposite sides = TRANS isomer

Question 22

bonds can be broken hetrolytically

Answer 22

hetrolytic fission

Question 23

electrophile

Answer 23

species attracted to an area of high electron density

can accept a pair of e-

may or may not be charged

Question 24

electrophilic addition

Answer 24

happens to alkenes due to electron dense double bond

electrophiles attack double bond in alkenes

lead to formation of positive carbocation intermediate

Question 25

electrophilic addition of bromine

ethene

Answer 25

Question 26

asymetric alkene

Answer 26

groups or atoms attached to either end of the carbon-carbon double bond are different.

Question 27

reaction of asymetric alkenes with H-BR

Answer 27

Question 28

reaction of an asymmetric alkene

Answer 28

Question 29

overall reaction free radical substitution

Answer 29

Question 30

overall reaction free radical substitution

Answer 30