6 - Organic I

Question 1

homologous series definition

Answer 1

series of hydrocarbons with the same general formula

Question 2

which organisation sets out how to name organic compounds

Answer 2

IUPAC

Question 3

general formula for alkanes

Answer 3

Cn H2n+2

Question 4

how to make fuel

Answer 4

1) crude oil goes to fractional distillation
2) cracking with 650°C and alumina catalyst
3) fractional distillation again
4) reforming

Question 5

what does reforming mean

Answer 5

converting long chain hydrocarbons to branched or cyclic isomers to make them more easily combustible

Question 6

what is reforming

Answer 6

chambers lined with solid catalysts like Pd, Pt or Rh

Question 7

why are branched/cyclic molecules easier to combust

Answer 7

• can’t pack together easily
• weaker london forces
• more volatile

Question 8

which pollutants are formed by combusting fuels

Answer 8

• CO from incomplete combustion
• Sulfur Oxides
• Nitrous Oxides
• unburned hydrocarbons

Question 9

why are sulfur oxides bad

Answer 9

• So2 reacts with H2O in the air to form H2SO2, sulfurous acid
• weak acid but strong enough to harm plants and fish

Question 10

why are nitrous oxides bad

Answer 10

• NO causes acid rain

- NO2 causes respiratory issues

Question 11

why is carbon monoxide bad

Answer 11

binds with haemoglobin to form carboxyhaemoglobin which prevents binding of oxygen

Question 12

what is a radical

Answer 12

a species with an unpaired electron

Question 13

how is a radical formed

Answer 13

homolytic fission of a covalent bond

Question 14

steps of alkane + halogen

Answer 14

1) initiation: Br - Br –> 2Br° using UV light
2) propagation: CH4 + Br° –> CH3° + HBr
CH3° + Br2 –> CH3Br + Br°
3) termination: 2CH3° –> C2H6
2Br° –> Br2
CH3° + Br° –> CH3Br

Question 15

issues of halogen substitution

Answer 15

• low yield because you cannot prevent multiple substitutions, or prevent where substitutions take place
• a mixture of products is formed

Question 16

general formula of alkenes

Answer 16

CnH2n

Question 17

what bonding is present in alkenes and how does that affect their reactivity

Answer 17

• pi and sigma bonds

- pi bonds have side on overlap. This drags electrons at an angle, making it weaker and easier to break

Question 18

why do alkenes have geometric isomers?

Answer 18

restricted rotation around the C=C bond

Question 19

what is an electrophile

Answer 19

electron pair acceptor

Question 20

reduction of alkenes

Answer 20

• add H2
• nickel catalyst
• 150°C
• saturates the alkene. used to make margarine from vegetable oils, to saturate the fats

Question 21

oxidation of alkenes

Answer 21

• KMno4 (aq)
• H2SO4 (aq)
• makes diol

Question 22

carbocation stability highest to lowest

Answer 22

3°
2°
1°

Question 23

draw the mechanism for electrophilic addition of HBr to propene

Answer 23

check

Question 24

draw the mechanism for ethene + steam

Answer 24

check

Question 25

draw the mechanism for propene and bromine water

Answer 25

check

Question 26

how are ions formed?

Answer 26

heterolytic bond fission of a covalent bond

Question 27

how can you dispose of waste polymers

Answer 27

- recycle - incinerate - leave to decompose - use as feedstock for cracking

Question 28

how do scientists limit problems of polymer disposal?

Answer 28

- create biodegradable polymers | - remove toxic gases produced by incineration of polymers

Question 29

what is a nucleophile

Answer 29

electron pair donor

Question 30

what bonds do halogenoalkanes form

Answer 30

- london forces | - dipole dipole due to difference in electronegativity of halogens and carbon

Question 31

what is SN1

Answer 31

- nucleophilic substitution 1 - 1 thing in rate equation - tertiary halogenoalkanes - forms carbocation

Question 32

what is SN2

Answer 32

- nucleophilic substitution 2 - 2 things in rate equation - primary halogenoalkanes - forms intermediate

Question 33

draw the mechanism for SN1

Answer 33

check

Question 34

draw the mechanism for SN2

Answer 34

check

Question 35

draw the mechanism for halogenoalkanes + KOH (aq)

Answer 35

check

Question 36

mechanism for halogenoalkanes + AgNO3 (aq) in ethanol

Answer 36

- nucleophilic substitution - NO3- is too stable so H2O is the nucleophile - H20 is not negative so is a weak nucleophile so slow reaction - silver halide formed so white ppt. seen - check mechanism

Question 37

mechanism for halogenoalkane + KCN (ethanol)

Answer 37

- nucleophilic substitution - can't be aqueous as OH- is a better nucleophile - makes a nitrile, increasing the carbon chain by 1 - check mechanism

Question 38

mechanism for halogenoalkane + NH3 (ethanol)

Answer 38

- nucleophilic substitution - ammonia is a good nucleophile so it donates electrons to a H, forming NH4 + - poor yield due to multiple substitutions

Question 39

mechanism for halogenoalkane + KOH (ethanol)

Answer 39

- elimination - makes alkene - check mechanism - OH- acts as a base

Question 40

which halogenoalkane has the fastest hydrolysis rate and why

Answer 40

- iodoalkane - longer and therefore weaker bonds - lower activation energy

Question 41

do tertiary or primary halogenoalkanes have faster hydrolysis rates and why

Answer 41

- tertiary have higher rate than primary - tertiary always do SN1 which is faster - in SN2 you release halogen and add nucleophile at the same time, so has higher activation energy

Question 42

how can you compare rates of halogenoalkane hydrolysis

Answer 42

add aqueous silver nitrate in ethanol