Concept explainers
Interpretation:
Two most stable Lewis structures for thiocyanate ion are to be written and the atom in each of them that bears a formal charge
Concept introduction:
The formal charge of an atom is calculated by the following formula:
Thiocyanate ion is a good nucleophile and reacts with a primary
Constitutional isomers have the same molecular formula but differ in the connectivity of atoms in their structure.
Answer to Problem 23P
Solution:
a) The stable Lewis structures for thiocyanate ion are:
In structure I, the sulfur atom has a formal charge of
b) The structures of the two constitutional isomers of
Explanation of Solution
a) Thiocyanate ion,
The total number of valence electrons in
The two stable Lewis structures of the thiocyanate ion are shown below:
Carbon belongs to Group
In structure I, the electron counts and formal charge for each atom are as follows:
Hence, in structure I, the sulfur atom has a formal charge of
In structure
Hence, in structure
b)
In the reaction given, the alkyl halide is a primary alkyl bromide. The nucleophile is thiocyanate ion, formed by the dissociation of
Thiocyanate ion has two nucleophilic centers, which means it can attack through either sulfur or nitrogen atom. Because of this, when thiocyanate is used as a nucleophile, two possible products are obtained. In one product, the nucleophile attacks through the sulfur atom and gets attached to the carbon atom in the alkyl halide. In the other product, the nucleophile attacks through the nitrogen atom and gets attached to the carbon atom in the alkyl halide. The molecular formula of both the products remains the same; only the connectivity of atoms is different. Hence, they form constitutional isomers as follows:
Thus, the structures of the two constitutionally isomeric products of the molecular formula
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