Alcohols And Haloalkanes

Question 1

Alcohol properties

Answer 1

Less volatile
Higher mp - form h bonds
greater solubility due to the polarity of the molecules (decreases as chain gets longer as less of effect on wider molecule)

Question 2

Classifying alcohols

Answer 2

•Primary alcohol- OH group attached to carbon attached to 2 H and alkyl group
•Secondary alcohol- OH group attached to 1 H bond and 2 alkyl groups
•Tertiary alcohols - OH group is attached to C w no hydrogen all alkyl

Question 3

Oxidation of alcohols

Answer 3

Acidified dichromate ions
If alcohol oxidised these reduced from orange to green
Cr2O7 2- => Cr3+

Question 4

Oxidation of primary alcohol

Answer 4

+ [O] => aldehyde heat + distil to prevent further reaction

+2[O]=> Carboxylic acid heat strong under reflux

Question 5

Oxidation of secondary alcohols

Answer 5

+ [O] => ketone heat under reflux to ensure fully reacted

Question 6

Oxidation of tertiary alcohols

Answer 6

Don’t undergo oxidation reactions
Acidified dichromate remains orange

Question 7

Dehydration of alcohols

Answer 7

Heat under reflux with acid catalyst eg conc H2SO4
Product is Alkene
Reaction is elimination water is removed

Question 8

Substitution reactions of alcohols

Answer 8

Nucleophilic
React w hydrogen halides form haloalkanes
Heat under reflux w sodium halide and sulfuric acid HBr is formed react to form haloalkane

Question 9

Reactivity of haloalkanes

Answer 9

Carbon halogen bond is polar
Carbon ion has a slight positive charge which attracts nucleophiles
Nucleophiles replace halogen - nucleophilic sub

Question 10

Hydrolysis

Answer 10

OH- ion replaces halogen
Carbon halogen bond is broken by heterolytic fission
Alcohol is formed
Use NaOH heated under reflux

Question 11

Carbon halogen strength

Answer 11

Lower down the group the weaker the carbon halogen bond the more reactive and easier to break down
Rate of hydrolysis increases as the strength of the carbon halogen bond decreases

Question 12

Hydrolysis of primary secondary and tertiary haloalkanes

Answer 12

Tertiary rate is the fastest due to the increased stability of the tertiary carbocation

Question 13

Organohalogens

Answer 13

Molecules that contain at least one halogen atom joined to carbon chain
Rarely found in nature as they aren’t broken down naturally - concern

Question 14

Ozone layer

Answer 14

Found at outer edge of stratosphere absorb damaging uv radiation
Depletion in this leads to damage to species causing more cancer

Question 15

UV forming ozone

Answer 15

UV breaks O2 down into O radicals
O2 molecules react with O radical which forms ozone
Rate formed= rate broken down

Question 16

CFCs

Answer 16

Chlorofluorocarbons very stable due to the strength of carbon halogen bond
Stable until reach the stratosphere where they are broken into Cl • which catalyse breakdown of ozone

Question 17

How do cfcs breakdown ozone

Answer 17

CFCs are broken down via radiation process is photodisociation
Forms CF2Cl• + Cl•
Propagation 1. Cl• +O3 -> ClO• +O2
2. ClO• + O-> Cl• + O2
O3+O -> 2O2

Question 18

Other ozone depleting reactions

Answer 18

Nitrogen oxide radicals form during lightning strikes and aircraft travel
NO• +O3 -> NO2• + O2
NO2• + O -> NO• + O2
O3+ O -> 2O2