Question

A violet colour with sodium nitroprusside in the test of sulphur in an organic compound is due to the formation of:
A.$Na{}_{4}\left[ Fe\left( CN \right){}_{5}NO \right]$
B.$Na{}_{4}\left[ Fe\left( CN \right){}_{5}NOS \right]$
C.$Na{}_{3}\left[ Fe\left( CN \right){}_{5}NS \right]$
D.$Fe{}_{4}\left[ Fe\left( CN \right){}_{6} \right]{}_{3}$

Answer 1

Hint: Lassaigne test is the test, the organic compound is fused with metallic sodium to convert elements into water soluble sodium salt. Lassaigne test is held to detect the nitrogen, sulphur, bromine, chlorine and iodine. It was developed by the French chemist J.L Lassaigne

Complete step by step answer:
First we will discuss about nitroprusside reaction
Nitroprusside reaction is a chemical test used to detect the presence of cytonin in protein. Protein with thiol group gives a red colour when there is a solution of sodium nitroprusside in aqueous ammonia. Sodium nitroprusside was discovered as early as 1850 and found to be useful in medicine in 1928. It is the safest and most effective drug.
According to the question, now we will discuss the sodium nitroprusside test or “Lassaign’s test.
The element present in the compound is converting from covalent to the ionic bond.
Take 1 ml of sodium extract in the test tube and add a few drops of sodium nitroprusside solution and shake. Appearance of purple colour confirmed the presence of Sulphur. Sulphur present in the organic compound; sodium fusion is converting into sodium sulphide. Sulphide ions are readily identified using sodium nitroprusside.
Sulphide of sodium is formed on sodium fusion and is extracted from the fused mass by boiling it with distilled water. This extract is known as sodium fusion extract.
$Na+S\to Na{}_{2}S$
Sulphide ions are readily identified using sodium nitroprusside.
$Na{}_{2}S+Na{}_{2}\left[ Fe\left( CN \right){}_{5}NO \right]\to Na{}_{4}\left[ Fe\left( CN \right){}_{5}NOS \right]$
Sodium nitroprusside sodium thio nitroprusside

Hence, the correct option is (B).


Note:
Nitroprusside is used predominantly to treat hypertensive emergencies, such as to lower blood pressure during acute aortic dissection or to improve cardiac output in severe congestive heart failure.