Which of the following has the weakest carbon-carbon bond strength?
C2H6
As the number of shared electrons increases, the bond strength increases.
In a triple bond, totally 6 electrons are shared. In a double bond, totally 4 electrons are shared and in a single bond, only 2 electrons are shared. Thus, the bond strength is as follows:
Triple bond > double bond > single bond. Therefore, C2H6 has weakest carbon-carbon bond strength because it is an alkane with carbon-catbon single bonds.