Which of the following allylic carbocations is the most stable?

Step-by-step solution

The stability of carbocations increases with the number of electron-donating groups (+I effect) and the number of -hydrogens (hyperconjugation). All the given species are allylic carbocations and are stabilized by resonance. Their relative stabilities can be determined by the degree of the carbon bearing the positive charge: For CH ₃- CH = CH - C H - CH ₃ , the carbocation is secondary ( 2^ ) allylic and has 3 -hydrogens. For CH ₃- CH = CH - C ( CH ₃)₂ , the carbocation is tertiary ( 3^ ) allylic and has 6 -hydroge