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