CH3-CH3 -> CH3-CH2Cl (Cl2)
CH3-CH2Cl -> CH3-CH2-CH2-CH3 (Zn/Cu)
CH3-CH2-CH2-CH3 -> CH3-CH=CH-CH3 (CH3I/KOH)
CH3-CH3 -> CH3-CH2Cl (Cl2)
CH3-CH2Cl -> CH3-CH2-CH2-CH3 (Zn/Cu)
CH3-CH2-CH2-CH3 -> CH3-CH=CH-CH3 (CH3I/KOH)