Question

An organic compound \[ X \] is oxidised by using acidified \[{K_2}C{r_2}{O_7}\] solution. The product obtained reacts with phenylhydrazine but does not answer the silver mirror test. The compound \[ X \] is :
A. \[2 - propanol\]
B. Ethanal
C. Ethanol
D. \[C{H_3}C{H_2}C{H_3}\]

Answer 1

Hint: Secondary alcohols like \[2 - propanol\] go reaction under oxidization to ketones and if you heat the secondary alcohol \[2 - propanol\] with sodium \[Na\] or potassium dichromate solution which is a made acidified with dilute sulfuric acid, there is formation of propanone and changing the conditions of reaction makes no difference to the product.

Complete answer
Potassium dichromate is a basically an inorganic reagent chemical which is commonly used as an oxidizing agent in various field and industry applications. As with all chromium type compounds, it affects health adversely and is harmful to health. It is a crystalline ionic in a solid state with a very bright color of red-orange. Potassium dichromate \[{K_2}C{r_2}{O_7}\] is usually prepared by the reaction between potassium-chloride \[KCl\] and sodium di-chromate. Alternatively, it can be also obtained from potassium chromate after chromite ore roast with potassium hydroxide.
Potassium dichromate \[{K_2}C{r_2}{O_7}\] and its acidic solution is an orange colored solution which changes to green color when the alcohol oxidises. This reaction can be used as a testing for alcohols detection and only alcohol category will show the orange to green colour transformation with acidified potassium dichromate solution.
As this compound does not provide silver mirror test, it cannot be an Aldehyde, Also it reacts with phenyl-hydrazine and therefore, it has to be a ketone which is obtained only when the compound is \[2 - propanol\].

Therefore, the correct answer is option A. \[2 - propanol\].

Note:
Potassium dichromate \[{K_2}C{r_2}{O_7}\] has few major applications, as the sodium salt is dominant industrial, the main application of this compound is in leather tanning industries and various laboratories.