new index atom name original index 1 C 8 2 C 7 3 C 5 4 C 6 5 C 3 6 C 4 7 O 2 8 O 1 9 H 17 10 H 18 11 H 15 12 H 16 13 H 11 14 H 12 15 H 13 16 H 14 17 H 10 18 H 9 19 H 20 20 H 19