new index atom name original index 1 C 1 2 C 6 3 C 7 4 C 2 5 C 5 6 C 8 7 C 11 8 N 10 9 N 4 10 O 3 11 O 9 12 O 12 13 O 13 14 H 15 15 H 16 16 H 14 17 H 19 18 H 20 19 H 21 20 H 22 21 H 18 22 H 23 23 H 24 24 H 17 25 H 25