new index atom name original index 1 C 3 2 C 5 3 C 4 4 C 6 5 C 7 6 C 8 7 O 1 8 O 2 9 H 9 10 H 10 11 H 13 12 H 14 13 H 11 14 H 12 15 H 15 16 H 16