Question

CH2=CH2->CH3-CH2-Br->CH3-CH2-CH2-CH3->CH2=CH-CH=CH2

Answer 1

ch2ch2+hbr=ch3ch2br
ch3ch2br+2na+ch3ch2br=ch3ch2ch2ch3+2nabr
ch3ch2ch2ch3=(al2o3, t)=ch2=ch-ch=ch2