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