Which of the following alkenes yield 3-bromo- | vedclass

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(A) The addition of $HBr$ to alkenes follows Markovnikov's rule,where the electrophile $H^+$ adds to the carbon with more hydrogens,forming the most s

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$I$ and $II$ only

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(A) The addition of $HBr$ to alkenes follows Markovnikov's rule,where the electrophile $H^+$ adds to the carbon with more hydrogens,forming the most stable carbocation intermediate.$3-$bromo$-3-$methylpentane has the structure $CH_3CH_2C(Br)(CH_3)CH_2CH_3$.To obtain this product,the intermediate carbocation must be the $3-$methylpentan$-3-$yl cation $(CH_3CH_2C^+(CH_3)CH_2CH_3)$,which is a tertiary carbocation.$(I)$ $3-$methylpent$-2-$ene $(CH_3CH_2C(CH_3)=CHCH_3)$: Protonation at $C2$ gives the $3-$methylpentan$-3-$yl cation.$(II)$ $3-$methylpent$-2-$ene (isomer): Protonation at $C2$ gives the $3-$methylpentan$-3-$yl cation.$(III)$ $3-$ethylpent$-1-$ene $(CH_3CH_2C(CH_2CH_3)=CH_2)$: Protonation at $C1$ gives the $3-$ethylpentan$-3-$yl cation,which is a tertiary carbocation,but it leads to $3-$bromo$-3-$ethylpentane,not $3-$bromo$-3-$methylpentane.$(IV)$ $3-$methylpent$-1-$ene $(CH_3CH_2CH(CH_3)CH=CH_2)$: Protonation at $C1$ gives a secondary carbocation,which rearranges to a more stable tertiary carbocation,but not the specific one required.Thus,only structures $(I)$ and $(II)$ yield the desired product.

Which of the following alkenes yield $3-$bromo$-3-$methylpentane as the major product upon addition of $HBr$?
$(I)$ $3-$methylpent$-2-$ene
$(II)$ $3-$methylpent$-2-$ene (isomer)
$(III)$ $3-$ethylpent$-1-$ene
$(IV)$ $3-$methylpent$-1-$ene

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Which of the following alkenes yield $3-$bromo$-3-$methylpentane as the major product upon addition of $HBr$?$(I)$ $3-$methylpent$-2-$ene$(II)$ $3-$methylpent$-2-$ene (isomer)$(III)$ $3-$ethylpent$-1-$ene$(IV)$ $3-$methylpent$-1-$ene