4.14 Alcohols ✓
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1
Which functional group do alcohols have?
-OH
2
What is the general formula for an alcohol?
$C_nH_{2n+1}OH$
3
What is methanol used for?
-high-performance fuel
-chemical feedstock
-polymers
-paints
-solvents
-insulation
-adhesives
-chemical feedstock
-polymers
-paints
-solvents
-insulation
-adhesives
4
Why is methanol used for high-performance fuels?
efficient combustion
5
What is ethanol used for?
-alcoholic drinks
-fuel
-solvent
-feedstock
-fuel
-solvent
-feedstock
6
What are the differences in properties between corresponding alkanes and alcohols?
-alcohols less volatile
-alcohols have higher mp
-alcohols have greater water solubility
-alcohols have higher mp
-alcohols have greater water solubility
7
Are alkanes polar? Why?
no as electronegativity oh H and C are very similar
8
Are alcohols polar? Why?
yes due to polar O-H bond (difference in electronegativity of O and H)
9
What are the intermolecular forces like between alkanes? Why?
very weak London forces due to being non-polar
10
What are the intermolecular forces like between alcohols?
very weak London forces + stronger H bonds between O-H groups
11
Why is there a difference in volatility and bp between alkanes and alcohols?
H bonds hold together alcohol molecules which require more energy to overcome than weak London forces in alkanes
12
Why is there a difference in solubility in water between alkanes and alcohols?
H bonds in alcohols make them more water soluble
13
How does chain length of alcohols affect solubility in water?
shortest chains completely soluble, but as chain increases influence of OH group decreases so solubility decreases
14
What is a primary alcohol?
carbon that -OH group is attached to is also attached to 2 H and 1 alkyl group
15
What is a secondary alcohol?
carbon that -OH group is attached to is also attached to 1 H and 2 alkyl groups
16
What is a tertiary alcohol?
carbon that -OH group is attached to is also attached to no H and 3 alkyl groups
17
What effect does increasing chain length in alcohol during combustion have?
increasing quantity of heat released per mole
18
What is usually used as the oxidising mixture?
solution of potassium dichromate (VI) acidified with dilute sulfuric acid
19
What happens to the solution containing dichromate(VI) ions if the alcohol is oxidised?
reduced from orange dichromate(VI) ions to green chromium (III) ions
20
Which 2 products can be formed when primary alcohols are oxidised?
aldehydes or carboxylic acids
21
What product is produced when aldehydes are oxidised?
carboxylic acids
22
Which conditions are required to produce aldehydes from primary alcohol oxidising?
-gentle heating with acidified potassium dichromate
-aldehyde distilled out of reaction mixture to prevent it further reacting/ oxidising
-aldehyde distilled out of reaction mixture to prevent it further reacting/ oxidising
23
How is an oxidising agent represented in a display formula?
[O]
24
Which conditions are required to produce carboxylic acids from primary alcohol oxidising?
-heated strongly under reflux
-excess of acidified potassium dichromate(VI)
-excess of acidified potassium dichromate(VI)
25
Why must a primary alcohol oxidise with excess acidified potassium dichromate(VI) to produce carboxylic acid?
ensures all alcohol oxidised fully into carboxylic acid
26
Why must a primary alcohol oxidise by heating under reflux to produce carboxylic acid?
ensures any aldehyde formed initially undergoes oxidation to form carboxylic acid
27
What do secondary alcohols oxidise into?
ketones
28
Why must a secondary alcohol oxidise by heating under reflux?
to ensure reaction goes to completion
29
Do tertiary alcohols oxidise?
no
30
What is a dehydration reaction?
reaction where water molecule removed from starting material
31
What type of reaction is dehydration of an alcohol an example of?
elimination reaction
32
What is the product when an alcohol is heated under reflux with an acid catalyst?
alkene
33
What are examples of acid catalysts used in dehydration reactions with alcohols?
-concentrated sulfuric acid
-concentrated phosphoric acid
-concentrated phosphoric acid
34
What is formed when alcohols react with hydrogen halides?
haloalkanes
35
How are haloalkanes formed from alcohols?
alcohol heated under reflux with sulfuric acid + sodium halide and hydrogen halide formed in place