The gas is chlorofluoro carbon. Its reaction in stratosphere is as follows : (i) CCl2F2+UV‌light‌→‌CClF2+Cl (ii) CCl3F+UV‌light‌→‌CCl2‌F+Cl (iii) Cl+O3→‌ClO+O2 (iv) ClO+O→‌Cl+O2 So, the intermediate in first step are Cl+CClF2.