Some Basic Concepts of Chemistry - Result Question 55
####54. An unknown compound of carbon, hydrogen and oxygen contains $69.77 % C$ and $11.63 % H$ and has a molecular weight of 86. It does not reduces Fehling’s solution but forms a bisulphate addition compound and gives a positive iodoform test. What is the possible structure(s) of unknown compound?
(1987, 3M)
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Solution:
- From the given elemental composition, empirical formula can be derived as :
| Element | $\mathbf{C}$ | $\mathbf{H}$ | $\mathbf{O}$ |
|---|---|---|---|
| Weight $%$ | 69.77 | 11.63 | 18.60 |
| Mole $%$ | 5.81 | 11.63 | 1.1625 (obtained by dividing from $M$ ) |
| Simple ratio | 5 | 10 | 1 |
Hence, empirical formula is $C _5 H _{10} O$ and empirical formula weight is 86 .
Since, empirical formula weight and molecular weight both are (86), empirical formula is the molecular formula also.
Also, the compound does not reduce Fehling’s solution, therefore it is not an aldehyde, but it forms bisulphite, it must be a ketone.
Also, it gives positive iodoform test, it must be a methyl ketone.
Based on the above information, the compound may be one of the following :
