Question

conversion of but-1-ene to but-2-ene

Answer 1

CH3-CH2-CH=CH2 +HBr--->

CH3-CH2-CH(Br)-CH3

This reaction happens according to Markonikoffs rule

Now reacting this with alcoholic KOH gives alkenes

CH3-CH2-CH(Br)-CH3 + KOH (alc)——-> CH3CH=CHCH3 + KBr + H2O

Answer 2

$\begin{array}{c c c} CH_3-CH_2-CH=CH_2 & \xrightarrow{dil. H_2SO_4} & \begin{aligned} &OH\\ &\ |\\ CH_3-CH_2-&CH-CH_3 \end{aligned}\\ \\ &&\bigg\downarrow H^+,\Delta \\ \\ &&CH_3-CH_2=CH-CH_2 \end{array}$