CH2=CHCH2CH3 - (+HCl, H2O2)-->X1 -(KOH,спирт)-->X2--(H2O,H,t)-->X3-->бутен-2 ---(+Br2)-->X4
CH2=CH-CH2-CH3+HCL=(H2O2)= CH2(Cl)-CH2-CH2-CH3
CH2(Cl)-CH2-CH2-CH3+KOH(спирт)=CH2=CH-CH2-CH3+KBr+H2O
CH2=CH-CH2-CH3+H2O=CH3-CH(OH)-CH2-CH3
CH3-CH(OH)-CH2-CH3=(H2So4)= CH3-CH=CH-CH3
CH3-CH=CH-CH3+Br2=CH3-CH(Br)-CH(Br)-CH3