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How many structural isomers with the molecular formula C4H8O give infra-red absorptions both at approximately '1200 cm^-1' and at approximately '3400 cm^-1'? - CIE - A-Level Chemistry - Question 30 - 2018 - Paper 1
Question 30
How many structural isomers with the molecular formula C4H8O give infra-red absorptions both at approximately '1200 cm^-1' and at approximately '3400 cm^-1'?
Worked Solution & Example Answer:How many structural isomers with the molecular formula C4H8O give infra-red absorptions both at approximately '1200 cm^-1' and at approximately '3400 cm^-1'? - CIE - A-Level Chemistry - Question 30 - 2018 - Paper 1
Step 1
Identify the infrared absorption characteristics
Answer
The absorption around 1200 cm^-1 typically corresponds to the presence of a C-O bond, suggesting that the isomers may include ethers or alcohols. The absorption at approximately 3400 cm^-1 is indicative of O-H stretching, which is characteristic of alcohols.
Step 2
Step 3
Determine which isomers provide the specified IR absorptions
Answer
Among the isomers, 1-Butanol, 2-Butanol, and Cyclobutanol will show both absorptions at 1200 cm^-1 and 3400 cm^-1 due to their C-O and O-H bonds. Aldehydes and ethers do not have the O-H bond, thus they will not count. Therefore, the three structural isomers are:
- 1-Butanol
- 2-Butanol
- Cyclobutanol.
Step 4
Count the total number of isomers
Answer
The total number of structural isomers of C4H8O that exhibit both IR absorptions is 3. However, since we're also accounting for distinct structures and not just functional groups, we conclude there are 4 distinct structural isomers that fit the requirement.