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Alkanols (1/5)
Alkanols
A) Introduction
Alkanols (or ____________ ) are a homologous series of organic compounds with general
formula ___________. The functional group is ___________________________ (_______).
Name
Structural Formula
CH3OH
CH3CH2OH
CH3CH2CH2OH
OH
CH3CH CH3
CH3CH2CH2CH2OH
OH
CH3CH CH2CH3
B) Uses of Alkanols
1. As fuels - methanol and ethanol burn readily in air with a clean flame.
- methylated spirit is the most widely used industrial alcohol.
- In Brazil, ethanol is made from sugar cane by fermentation. Then petrol and
ethanol are mixed as a fuel for vehicles. The mixture is called ______________.
2. As solvents – for cosmetics, perfumes and tincture of iodine (_______________)
- paints and dyes (___________________________)
3. Production of esters
Easters have _________________________ smell. They are used in cosmetics and artificial
flavourings. They are also good solvents for organic compounds.
*4. As alcoholic drinks
*5. Production of vinegar (a dilute solution of ___________________)
Some micro-organisms are added to a dilute solution of ethanol. The mixture is then exposed
to air for one or two weeks.
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C) Manufacture of Ethanol
Ethanol is the most important alkanol. It is commonly known as ‘alcohol’.
1) Catalytic Hydration of Ethene
H H
H C C H
Reaction condition: 1. high temperature (300oC)
2. high pressure (65 atm)
3. catalyst is used: _______________________
2) Fermentation
Definition: Fermentation is the slow breakdown of large organic molecules (e.g. starch or
sugar) to smaller molecules (e.g. ethanol) by micro-organisms (e.g. _____________)
The raw materials for fermentation are grape, barley, maize, rice and etc.
First starch is mixed with malt which contains an enzyme called ______________.
Then yeast is added which contains other enzymes called _____________ and
_____________.
The ethanol prepared by fermentation
is quite dilute (roughly 10%) because
yeast dies if the concentration of
ethanol is too high. The concentration
of ethanol can be increased by
______________________________.
solution
of glucose
with yeast
limewater
lim
ew
Fermentation of glucose in the laboratory
at
er
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D) Physical Properties of Alkanols
R OH
Alkyl group (hydrocarbon part)
- non-polar
- dissolve in oil but not water
Hydroxyl group (quite reactive)
- polar
- dissolve in water but not in oil
1) Solubility
Solubility of alkanols in water decreases when the number of carbon atoms increases because
the alkyl group has a ____________ influence. The higher alkanols have a lower solubility in
water.
Name of alkanols
Does it dissolve in water?
Does it dissolve in non-aqueous solvent?
Methanol
Ethanol
Propan-1-ol
Hexan-1-ol
2) Boiling point
The boiling point, melting point and density increase steadily as the number of carbon atoms
increases because the ____________________________ between the molecules becomes
____________.
E) Chemical Properties of Alkanols
1) Combustion
e.g.
2) Esterification
Definition: Esterification is the _______________ reaction of an alkanoic acid with an
alkanol to form an ester and water.
e.g.
__________________________________ is usually used as catalyst and heat is necessary.
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3) Oxidation
Alcohols in the form of RCH2OH can be oxidized in two stages:
H
R C OH
[O]
H
e.g.
Step 1: Heating the reaction mixture under reflux
The condenser can prevent the loss of volatile substances on prolonged heating, and
favours the reaction to go to completion.
Step 2: Distilling the product mixture
To separate ethanoic acid from the mixture by distillation.
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F) Effects of Alcohol
1) Alcohol in the body
- alcohol quickly passes into the bloodstream
- Absorption is faster when there is no food in the stomach
- Alcohol is removed from the body in the _____________
Excessive drinking can lead to:
a) damage of the liver: ________________, _________________, ________________
b) brain damage
c) stomach ulcer
d) damage to the nervous system
e) damage to the baby if the pregnant woman drinks alcohol
2) Physiological Effects and Social Problems
a) Alcohol has a relaxing effect to people when taken in small amount. Nevertheless, many
people become addicted to it. They become ________________.
b) Drunken driver is one of the main causes of traffic accidents. Nowadays, a
________________ can be used to measure the concentration of alcohol in the breath of
the drivers.
SUMMARY
Burn in air
-
-
m.p., b.p. and density
increase with the
carbon atoms
solubility decreases
with the carbon atoms
Physical properties
Combustion
Oxidized to form alkanoic acids
React with alkanoic acids
Oxidation
Esterification
Chemical properties
Uses
ALKANOLS
2nd member
CnH2n+1OH / ROH
-
as fuel
as alcoholic drink
as solvent
-
as fuels
as solvents
to make esters
Ethanol
-
to make vinegar
to make ester