Q. 93.7( 3 Votes )
What is the correct order of decreasing stability of the following cations.
A. II > I > III
B. II > III > I
C. III > I > II
D. I > II > III
The carbocation is stabilized due to weak +I (inductive) effect of methyl groups (-CH3)
This carbocation is directly linked with –OCH3 group. Oxygen has 2 lone pairs of electrons so it readily donates a pair of electrons to stabilise the positive charge on carbon through +R effect(resonance by donating electrons) which is stronger than +I effect. Hence, this cation is highly stabilized.
In this case the –OCH3 group is attached farther from carbocation so will exhibit a weak –I effect( pulling of electrons towards itself). Hence, it is the least stable cation out the three.
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