2.9 Alcohol Flashcards
1
Q
alcohol can be classified into ?
A
primary
secondary
tertiary
2
Q
CH3 CH2 CH2 OH
name
class
A
propan - 1 - ol
primary
3
Q
CH3 CH2 CH(OH) CH3
name
class
A
butan - 2 - ol
secondary
4
Q
(CH3)3 OH
name
class
A
2-methylpropan-2-ol
tertiary
5
Q
why alcohols are more reactive than alkanes?
A
C–OH bond is polarised
C slightly + is susceptible to attack by nucleophiles
6
Q
reactions of alcohols
give 2
A
- combustion
2. metallic sodium
7
Q
how ethanol is made
A
fermentation of sugar cain or grain
8
Q
- combustion of alcohols
A
- combustion
alcohol burns to give CO2 and water
burns with blue flame and little soot
eq refers to note pg 2
9
Q
- reaction of alcohols with metallic sodium
A
- metallic sodium
sodium very reactive
forces hydrogen in -OH to behave like an acidic hydrogen
sodium replaces hydrogen in this reaction to form hydrogen gas
eq refers to notes pg2
if excess ethanol is evaporated, sodium ethoxide ( ionic compound) is seen as a white solid
10
Q
sodium and water
A
eq refer notes pg 2
11
Q
sodium in water
A
flame and quite vigorous due to exothermic reaction which the heat reacted with h2 produced
effervescence
sodium hydroxide soluble is water
sodium floats
12
Q
sodium in ethanol
A
no flame and less vigorous
effervescence by h2
sodium ethoxide seen as white solid and dissolves slowly as it pulls moisture from surrounding
sodium do not float
13
Q
other than water and alcohol
what else react vigorously with sodium to produce bubbles
A
acid
write eq refer notes pg 3
14
Q
propan - 1- ol when burns
eq
A
refer to notes pg 3
15
Q
sodium and propan - 1 - ol
eq
A
refer to notes pg 3
16
Q
types of reaction with alcohols
name 3
A
substitution
oxidation
dehydration / elimination
17
Q
substitution of alcohols -OH substituted by a halogen atom
- formation of chloroalkane
eq reagent condition product reaction type observation
test for hydroxyl group presence in carboxylic acid
A
eq: refer to notes
reagent: solid phosphorus pentachloride
condition: room temp, dry test tube
product: chloroethane ( reactant : ehthanol )
reaction type : nucleophilic substitution
observation: steamy fumes ( HCL)
18
Q
- formation of chloroalkane
why dry test tube is used
A
avoid reaction btwn phosphorus pentachloride with water
to form steamy fumes
19
Q
- formation of chloroalkane
HCL is colourless gas but why appears as steamy fumes
A
reacted with moist air
20
Q
- formation of chloroalkane
reagent used to test for HCL gas
A
glass rod dipped in conc ammonia form white smoke
ammonium cloride
21
Q
substitution of alcohols -OH substituted by a halogen atom
- formation of bromoalkane
eq reagent condition product reaction type observation
A
eq: refer to notes
reagent: sodium bromide plus 50 % conc sulphuric acid
( to prevent further oxidation of HBR to Br2 )
condition: heat under reflux
product: bromoethane ( reactant : ethanol )
reaction type : nucleophilic substitution
22
Q
procedure to make bromoethane from ethanol
A
- place a mixture of water, NaBr and ethanol in a round bottom flask ( ensure even heating )
- slowly add conc sulfuric acid drop by drop to the mixture
- heat the mixture under reflux for 45 mins
23
Q
- formation of bromoalkane
why water is used
A
to dilute conc H2SO4
it will further oxidised HBr to Br2
24
Q
- formation of bromoalkane
what is reflux
A
continual boiling and condensing of a reaction mixture
without the contents of the flask boiling dry
25
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
draw diagram for distillation
refer to notes pg 5
26
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
why mixture is distilled off
to separate volatile substance from involatile sodium acid and salt
27
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
why distillate is immersed in cold water
bromoalkane is volatile
to prevent evaporation
28
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the distillate forms two layers
what is the orgainc layer
unreacted ethanol
1 - bromoethane ( desired product )
29
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
what is the inorgainc layer
HBr
water
residual ethanol
30
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
draw the diagram
refer notes pg 5
31
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
how the process is being done
add water to the separating funnel and shake
allow two layers to separate and discard the lower aq layers
repeat twice the washing with water
discard lower aq layer each time
32
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
why water is added
to remove residual alcohol as ethanol is soluble in water
33
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
then wash with ?
wash with sodium carbonate solution
carefully releasing the pressure at intervals
shake and discard aq layer
34
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
then wash with sodium carbonate solution
why sodium carbonate is used
to remove the acid which dissolved in organic layer
35
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
then wash with sodium carbonate solution
why pressure is periodically released?
to released the presence due to co2 form
36
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
then wash with sodium carbonate solution
run off the organic layer into small conical flask, then add a little ?
add anhydrous calcium chloride
swirl the mixture until clear
37
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
then wash with sodium carbonate solution
run off the organic layer into small conical flask, then add a little anhydrous calcium chloride.
what is the function of anhydrous calcium chloride?
a drying agent to remove trace of water
38
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
then wash with sodium carbonate solution
run off the organic layer into small conical flask, then add a little anhydrous calcium chloride.
why initially mixture is cloudy?
cloudiness means mixture is not dry due to presence of tiny water droplet in bromoethane
39
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
then wash with sodium carbonate solution
run off the organic layer into small conical flask, then add a little anhydrous calcium chloride.
decant the liquid into?
decant into a dry distillation flask
| product is redistilled
40
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
then wash with sodium carbonate solution
run off the organic layer into small conical flask, then add a little anhydrous calcium chloride.
decant the liquid into distilled flask.
what is meant by decant?
pour off the liquid, leaving the solid behind
41
2. formation of bromoalkane
distillation
to distil off crude bromoethane and collect the distillate at 95 and 105 degree celsius
the two layers form in the distillate is separated using separating funnel
then wash with sodium carbonate solution
run off the organic layer into small conical flask, then add a little anhydrous calcium chloride.
decant the liquid into distilled flask.
why need to redistill?
to check the purity of bromoethane
temp 36 - 39 degree celcius
42
substitution of alcohols -OH substituted by a halogen atom
3. formation of iodoalkane
```
eq
reagent
condition
product
reaction type
```
eq: refer to notes
reagent: iodine, moist red phosphorus
condition: heat under reflux
product: iodoethane ( reactant: ethanol )
reaction type: nucleophilic substitution
43
substitution of alcohols -OH substituted by a halogen atom
3. formation of iodoalkane
why sodium iodide and 50% conc sulfuric aicd cannot be used as a reagent to convert ethanol to iodoethane
even 50 % H2SO4 will oxidise HI completely to I2
yield is very low
44
another way to form chloroalkane
follow bromoethane
reagent: conc H2SO4 and NaCl
H2SO4 no longer 50% conc because Cl cannot be further oxidised
condition: heat under reflux
45
oxidation reactions of alcohols
oxidising agent use
acidified K2Cr2O7
46
oxidation reactions of alcohols
primary alcohols oxidised to ?
aldehyde and carboxylic acid
47
oxidation reactions of alcohols
secondary alcohols oxidised to?
ketone
48
oxidation reactions of alcohols
tertiary alcohols oxidised to?
nothing
cannot be oxidised
49
oxidation reactions of alcohols
oxidation of primary alcohol to aldehyde
```
eq
reagent
condition
product
reaction type
observation
```
eq refer to notes
reagent: potassium dichromate (VI) solution and sulfuric acid ( to supply H+ so dichromate ( VI ) turns Cr3+ to green )
condition: distillation
product: ethanal ( reactant : ethanol, primary )
reaction type: oxidation
observation: orange solution turns green
50
oxidation reactions of alcohols
oxidation of primary alcohol to aldehyde
draw diagram of distillation
refer notes pg 8
51
oxidation reactions of alcohols
oxidation of primary alcohol to aldehyde
why distillation
to prevent further oxidation of aldehyde
distill off aldehyde as it forms
52
oxidation reactions of alcohols
oxidation of primary alcohol to carboxylic acid
```
eq
reagent
condition
product
reaction type
observation
```
eq refer to notes
reagent: potassium dichromate (VI) solution and sulfuric acid ( to supply H+ so dichromate ( VI ) turns Cr3+ to green )
condition: heating under reflux
product: ethanoic acid ( reactant: ethanol, primary )
reaction type: oxidation
observation: orange turns green
53
oxidation reactions of alcohols
oxidation of primary alcohol to carboxylic acid
heating under reflux
draw diagram
refer to notes pg 9
54
oxidation reactions of alcohols
oxidation of primary alcohol
why H2SO4 is added slowly
reaction is exothermic
55
oxidation reactions of alcohols
oxidation of primary alcohol
why is it necessary to cool the mixture while adding acid
to prevent mixture heating too rapidly
cause ethnanol to evaporate
56
oxidation reactions of alcohols
oxidation of primary alcohol
purpose of anti bumping granules
prevent super heating/violent heating
effect known as bumping, very hazardous
57
oxidation reactions of alcohols
oxidation of primary alcohol
why water bath is used rather than heating flask directly with bunsen flame
alcohol is flammable
uniform heating
58
oxidation reactions of alcohols
oxidation of primary alcohol
after heating, ethanoic acid was separated and washed and dried with drying agent
finally purify the ethanoic aicid in a narrow temp range
what is the temp range?
117 to 119 degree celcius
59
oxidation reactions of alcohols
oxidation of secondary alcohol to ketone
```
eq
reagent
condition
product
reaction type
observation
```
eq: refer to notes pg 11
reagent: potassium dichromate (VI) solution and sulfuric acid ( to supply H+ so dichromate ( VI ) turns Cr3+ to green )
condition: heating under reflux
product: propanone ( reactant: propan-2ol secondary
reaction type: oxidation
observation: orange to green
60
why ketone and tertiary alcohol cannot be further oxidised?
during oxidation, hydrogen atom from OH- group and the one attached to the carbon atom of OH- are removed to produce water.
in tertiary alcohol, there is only one hydrogen atom from the carbon that is attached to OH-
is want to be oxidised, C---C bond needs to be broken which is impossible for ketone and tertiary alcohol
C---C bond is very strong, C---H is very easy to break
61
how to comfirm presence of -OH bond in alcohol
give two tests
add Na. effervescence
add PCl5 dry. misty fumes
62
how to distinguish primary and secondary alcohols from tertiary
add K2Cr2O7 / dilute H2SO4 . orange to green
63
how to identify alcohol structural for alcohol
spectrometry analysis
64
dehydration of alcohols
draw diagram
refer to note pg 12
65
dehydration of alcohols
heat the granules gently and collect 4 test tubes of gas discarding the first one
why?
not the product
reaction has not taken place when heating just started
expantion of air due to heating
66
dehydration of alcohols
why aluminium oxide granules are used
act as catalyst
67
dehydration of alcohols
why the delivery tube needs to be removed from the water first before the source of heat is removed?
prevent suck back
test tube will crack and explode
68
dehydration of alcohols
test flammability of gas collected
yellow flame
flammable
69
dehydration of alcohols
bromine water i added into gas
reddish brown colour is decolourised
70
dehydration of alcohols
acidified solution of potassium manganate ( VII ) is added to gas
purple colour is decolourised
71
dehydration of alcohols
yellow flame
reddish brown colour is decolourised
purple colour is decolourised
what is the nature if the product?
alkene is a product of elimination
