new index atom name original index 1 C 6 2 C 7 3 C 5 4 C 8 5 C 2 6 C 3 7 N 9 8 N 1 9 O 4 10 O 10 11 H 16 12 H 17 13 H 18 14 H 19 15 H 14 16 H 15 17 H 20 18 H 21 19 H 13 20 H 22 21 H 23 22 H 11 23 H 12 24 H 24