This question is about compounds with the molecular formula C6H12O2.
Hexanoic acid, C5H11COOH, is a weak acid.
(1)
[pKa of hexanoic acid = 4.88]
(4)
The solubility of hexanoic acid in water is 1.08 g per 100 g of water.
The isomer of hexanoic acid, butyl ethanoate, CH3CO2C4H9, has a solubility of 0.68 g per 100 g of water.
Explain the differences in these data in terms of the hydrogen bonding between hexanoic acid and water, and between butyl ethanoate and water.
(3)
Compound A is thought to be another isomer of hexanoic acid.
10 g of compound A is found to contain 6.21 g of carbon and 1.03 g of hydrogen, with the remainder being oxygen.
Use the data to calculate the empirical formula of compound A.
You must show all your working.
(3)
(1)
A series of tests was performed on compound A.
Test | Observation | |
1 | addition of phosphorus(V) chloride | misty fumes |
2 | addition of 2,4-dinitrophenylhydrazine | orange precipitate |
3 | addition of Benedict’s or Fehling’s reagent | solution remains blue with no precipitate |
4 | addition of acidified potassium dichromate(VI) | solution remains orange |
5 | test using polarimetry | plane of plane polarised light is rotated |
Deduce the structure for compound A.
Justify your answer by using all the test results.
(6)
Compound B, another isomer with the molecular formula C6H12O2, contains a ring of six carbon atoms.
The carbon-13 NMR spectrum has only two peaks, one of which is at 69 ppm.
Draw the structure of compound B.
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