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Study the reaction scheme below and answer the questions that follow - Leaving Cert Chemistry - Question 8 - 2015
Question 8
Study the reaction scheme below and answer the questions that follow. C₃H₈ A x CH₃CHOHCH₃ B Y CH₃COCH₃ ... show full transcript
Worked Solution & Example Answer:Study the reaction scheme below and answer the questions that follow - Leaving Cert Chemistry - Question 8 - 2015
Step 1
Step 2
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Step 4
An isomer of compound B can be synthesised from an aldehyde. Name the isomer of compound B and the aldehyde and draw their full structural formulae.
Answer
The isomer of compound B is 1-propanol (or propan-1-ol), which can be synthesized from the aldehyde propanal (or propanaldehyde).
Structural formulae:
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Isomer (1-propanol):
CH₃-CH₂-CH₂-OH
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Aldehyde (propanal):
CH₃-CH₂-CHO
Step 5
How can the aldehyde be converted to the isomer of compound B?
Answer
The conversion of propanal (the aldehyde) to 1-propanol can be achieved through a reduction reaction. This can be performed using reagents such as hydrogen (H₂) with a catalyst like nickel (Ni) or using lithium aluminium hydride (LiAlH₄).
Step 6
The boiling points of compounds A, B and C are -48, -56 and 82 °C, but not necessarily in that order. For each compound, identify its boiling point, justifying your answer in terms of intermolecular forces.
Answer
Based on the nature of the compounds:
- A (Propene, boiling point -48 °C): Propene experiences weaker van der Waals forces due to its non-polar characteristics.
- B (2-propanol, boiling point -56 °C): 2-propanol is capable of hydrogen bonding due to its hydroxyl (-OH) group, leading to a comparatively lower boiling point than propanone.
- C (Propanone, boiling point 82 °C): Propanone (acetone) also has dipole-dipole interactions between molecules, along with some van der Waals forces, leading to a higher boiling point than the others.