Which of the following will be stable?
Generally, for checking the stability of a compound, we have to check for the stability of each constituent atom.
We know that,
→ Carbon can make four covalent bonds for stability
→ Bromine can make one
→ Hydrogen can make one
→ Nitrogen can make three.
Now, let's check each option one by one.
If we look at C(3), it is making only 3 covalent bonds.
But we know carbon makes 4 covalent bonds. Therefore, it will not be stable.
This compound will be stable because all carbons make 4 covalent bonds and Nitrogen makes 3 covalent bonds.
This compound will also be stable because all carbons make 4 covalent bonds.
In this compound, if we look at C(1) and C(4), carbon is only making three covalent bonds.
Therefore , it will not be stable. If we only take the molecular formula − C4H8 , there can be stable structures like cyclobutane. But since, the structural formula has clearly depicted that the first and the last carbon atoms have only 3 covalent bonds, this structure is not stable