A student was carrying out an investigation into alcohols, aldehydes and ketones - Scottish Highers Chemistry - Question 6 - 2017
Question 6
A student was carrying out an investigation into alcohols, aldehydes and ketones.
(i) Draw a structural formula for the secondary alcohol with the formula C4H10O.
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Worked Solution & Example Answer:A student was carrying out an investigation into alcohols, aldehydes and ketones - Scottish Highers Chemistry - Question 6 - 2017
Step 1
Draw a structural formula for the secondary alcohol with the formula C4H10O.
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Answer
The structural formula for the secondary alcohol with the formula C4H10O can be represented as:
H H H
| | |
H--C--C--OH
| |
H H
This indicates that carbon 2 has the hydroxyl group (–OH) attached, making it a secondary alcohol.
Step 2
Suggest why a water bath is an appropriate method of heating the reaction mixture.
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Answer
A water bath provides a controlled and even heat distribution, which reduces the risk of the alcohol catching fire compared to direct heating. This is crucial for maintaining a safe experimental environment.
Step 3
Describe the colour change that would have been observed with alcohols A and C.
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Answer
With alcohols A and C, the expected colour change when reacted with acidified dichromate solution would be from orange to green. This indicates the reduction of the dichromate ions as the alcohols are oxidised.
Step 4
State the type of alcohol that cannot be oxidised by acidified dichromate solution.
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Answer
Alcohol B is a tertiary alcohol, which cannot be oxidised by acidified dichromate solution due to the lack of a hydrogen atom on the carbon atom bearing the hydroxyl group.
Step 5
When alcohol A (C4H10O) is oxidised the product turns the pH paper red.
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The oxidation of alcohol A produces an acidic compound which is able to turn pH paper red, indicating an increase in acidity.
Step 6
Complete the ion-electron equation for the oxidation reaction.
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Answer
The complete ion-electron equation for the oxidation of alcohol A can be represented as follows:
C4H10O+H2OightarrowC4H8O2+4H++4e−
Step 7
Name the aldehyde that has a boiling point of 119°C.
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Answer
The aldehyde that has a boiling point of 119°C is 2-methylpentanal.
Step 8
Predict the boiling point, in °C, of the following molecule.
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Answer
The boiling point of the given molecule is predicted to be around 166°C to 181°C, which correlates with the structural characteristics that influence boiling points.
Step 9
Describe one way in which differences in structure affect the boiling point of isomeric aldehydes.
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One way in which the structure affects the boiling points is that increased branching in isomeric aldehydes generally lowers the boiling point due to decreased surface area and van der Waals forces.
Step 10
State what would be observed when an aldehyde is gently heated with Tollens’ reagent.
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When an aldehyde is gently heated with Tollens’ reagent, a silver mirror will form on the sides of the test tube, indicating the reduction of silver ions to metallic silver.
Step 11
Name the type of intermolecular interaction between ketone molecules.
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The type of intermolecular interaction between ketone molecules is predominantly dipole-dipole interaction due to the presence of the carbonyl group.
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