Thiols are compounds that contain an –SH functional group - Scottish Highers Chemistry - Question 6 - 2019
Question 6
Thiols are compounds that contain an –SH functional group. They often have very strong, unpleasant odours.
(a) Ethanethiol is used to add a smell to gaseous fuels i... show full transcript
Worked Solution & Example Answer:Thiols are compounds that contain an –SH functional group - Scottish Highers Chemistry - Question 6 - 2019
Step 1
State the reason why propan-1-ol was a suitable alcohol to compare with ethanethiol.
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Answer
Propan-1-ol has a similar molecular structure to ethanethiol, allowing for a meaningful comparison of boiling points based on intermolecular forces.
Step 2
Explain why propan-1-ol has a higher boiling point than ethanethiol. Your answer should include the names of the intermolecular forces broken when each liquid boils.
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Answer
Propan-1-ol has a higher boiling point (97 °C) than ethanethiol (35 °C) due to stronger hydrogen bonding present in propan-1-ol. The intermolecular forces in ethanethiol are mainly London dispersion forces, which are weaker than the hydrogen bonding in propan-1-ol. Therefore, more energy is required to break the intermolecular hydrogen bonds in propan-1-ol.
Step 3
Name the thiol that contains only one carbon atom.
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Answer
Methanethiol.
Step 4
Calculate the minimum mass of ethanethiol that needs to be present in a room containing 43,900 litres of air in order for it to be detected.
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Answer
First, convert the volume of air to cm².
1 litre = 1000 cm³, so:
43,900 litres = 43,900,000 cm³.
To find the total mass of ethanethiol needed to achieve the given concentration:
total concentration = 2.7 × 10⁻⁷ mg/cm² × 43,900,000 cm² = 11,853.7 mg ≈ 11.85 g.
Step 5
Suggest why 2-methyl-2-propanethiol is classified as a tertiary thiol.
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Answer
2-methyl-2-propanethiol is classified as a tertiary thiol because the sulfur atom is bonded to a carbon atom that is itself connected to three other carbon atoms.
Step 6
Draw the structure for the other isomer formed in this addition reaction.
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Answer
The other isomer formed would be a different arrangement of the carbon atoms; the structure can be depicted as follows:
H H
\
C
/ \
H C
|
S
|
C
/ \
H H
This shows 2,2-dimethylpropanethiol.
Step 7
Calculate the mass, in g, of 2-methyl-2-propanethiol made by the chemist.
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Answer
To find the mass of 2-methyl-2-propanethiol produced:
Theoretical mass = 30 g of 2-methylpropene × (GFM of 90g / GFM of 56g) = 48.21 g (theoretical yield).
Yield = 84% of 48.21 g = 0.84 × 48.21 g = 40.5 g.
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