Organic analysis

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Question 3
Medium

This question is about some structural isomers with the molecular formula C6H12O\text{C}_6\text{H}_{12}\text{O}C6​H12​O.

Five structural isomers of C6H12O: P (1-methylcyclopentan-1-ol), Q (cyclopentylmethanol), R (2-methylcyclopentan-1-ol), S (hexanal), and T (hexan-3-one)

a.

Identify the isomer(s) that would react when warmed with acidified potassium dichromate(VI).

State the expected observation when acidified potassium dichromate(VI) reacts.

[2]
b.

Identify the isomer(s) that would react with Tollens' reagent.

State the expected observation when Tollens' reagent reacts.

[2]
c.

Separate samples of each isomer are warmed with ethanoic acid and a few drops of concentrated sulfuric acid. In each case, the mixture is then poured into a solution of sodium hydrogencarbonate.

  • Identify the isomer(s) that would react with ethanoic acid.
  • Suggest a simple way to detect if the ethanoic acid reacts with each isomer.
  • Give a reason why the mixture is poured into sodium hydrogencarbonate solution.
[3]
d.

State the type of structural isomerism shown by isomers P, Q and R.

[1]
e.

Describe fully how infrared spectra can be used to distinguish between isomers Q, R and S. Use the following data in your answer:

  • O-H\text{O-H}O-H (alcohols): 3230–3550 cm−13230\text{--}3550\text{ cm}^{-1}3230–3550 cm−1
  • C=O\text{C=O}C=O (aldehydes/ketones): 1680–1750 cm−11680\text{--}1750\text{ cm}^{-1}1680–1750 cm−1
[4]
f.

State why mass spectrometry using electrospray ionisation is not a suitable method to distinguish between these isomers.

[1]

Organic analysis Questions

  1. A Level
  2. /Chemistry
  3. /Organic analysis