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