Upper C upper H subscript 4 (g) plus upper C l subscript 2 (g) right arrow upper C upper C l subscript 4 (g) plus upper H upper C l (g). Upper C upper H subscript 4 (g) plus 4 upper C l subscript 2 (g) right arrow upper C upper C l subscript 4 (g) plus 4 upper H upper C l (g). Upper C upper H subscript 4 (g) plus upper C l subscript 2 (g) plus upper H 2 (g) right arrow upper C upper C l subscript 4 (g) plus upper H upper C l (g).