new index atom name original index 1 C 1 2 C 2 3 C 4 4 C 3 5 C 5 6 C 6 7 C 7 8 C 8 9 N 9 10 O 13 11 O 10 12 O 11 13 O 12 14 O 14 15 O 15 16 P 16 17 H 18 18 H 17 19 H 19 20 H 20 21 H 23 22 H 21 23 H 22 24 H 24 25 H 25 26 H 26