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