The table shows the boiling points and structures of some isomers with molecular formula C8H16O2 - Scottish Highers Chemistry - Question 12 - 2016
Question 12
The table shows the boiling points and structures of some isomers with molecular formula C8H16O2.
| Isomer | Structure | Boiling point (°C) |
| ------- | --------- ... show full transcript
Worked Solution & Example Answer:The table shows the boiling points and structures of some isomers with molecular formula C8H16O2 - Scottish Highers Chemistry - Question 12 - 2016
Step 1
Name the intermolecular force which accounts for the higher boiling points of isomers 1, 2 and 3.
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Answer
The intermolecular force that accounts for the higher boiling points of isomers 1, 2, and 3 is hydrogen bonding.
Step 2
Using the information in the table, describe two ways in which differences in structure affect the boiling points of isomeric esters 4-8.
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Answer
More branching in the isomer generally leads to lower boiling points because the compact shape reduces the surface area available for interactions between molecules, thus weakening intermolecular forces.
The length and position of the ester link can influence the boiling point. For example, the closer the ester link is to the end of the molecule, the higher the boiling point due to increased polarity contribution from the –C=O group.
Step 3
Predict the boiling point, in °C, for the isomer shown below.
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Answer
The boiling point of the isomer shown is predicted to be between 99 °C and 124 °C based on structural similarity to isomers with known boiling points.
Step 4
Label each peak in the ethyl ethanoate spectrum with a number to match the carbon atom in ethyl ethanoate, shown below.
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Answer
Peaks labeled in order: 2, 3, 1, 4.
Step 5
Determine the number of peaks that would be seen in the carbon-13 NMR spectrum for the ester shown below.
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Answer
The ester shown would have 5 peaks in the carbon-13 NMR spectrum.
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