Question

In the reaction sequence${C_2}{H_5}Cl + KCN \xrightarrow{{C_2}{H_5}OH} X$, the molecular formula of X is:
A. ${C_2}{H_5}CN$
B. ${C_2}{H_5}NC$
C. ${C_2}{H_5}OH$
D. ${C_2}{H_8}O$

Answer 1

Hint: The cyanide ion is considered as an ambidentate ligand which is a nucleophile or a Lewis base. This means that the donation of the electron pair can take place through the nitrogen or the carbon site. This means it has two nucleophilic centers. KCN is considered as an ionic compound.

Complete answer:
Now see as the compound KCN is the ionic compound so it will undergo heterolytic fission thus forming the cation potassium and the anion cyanide. Here the attack would take place through the atom carbon not from the atom nitrogen as the carbon carbon single bond would be more stable as compared to the carbon nitrogen single bond, so the formation of alkyl cyanide takes place. The reaction would be as follows:
$RX + KCN \to R-CN + KX$
Here R is the alkyl group.
So now according to the question given when we will react with ethyl chloride with KCN under the presence of ethyl alcohol the formation of ethyl cyanide takes place. The reaction would be undergoing nucleophilic substitution reaction. The reaction for them is the following:
${C_2}{H_5}Cl +KCN \xrightarrow{{C_2}{H_5}OH} {C_2}{H_5}CN + KCl$
So the molecular formula of X will be ${C_2}{H_5}CN$.

Hence the correct answer is option A.

Note: The formation of ${C_2}{H_5}NC$ would have taken place when the ethyl chloride would have been reacted with AgCN. This so because on reacting with AgCN the nucleophile attacks through the nitrogen side instead of carbon side. This is so because the silver and carbon are bonded covalently due to the less electronegativity difference and the nitrogen is free to donate its electron pair.