You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Unambiguous structure elucidation of heterocyclic products from condensation-cyclisation reactions of enaminones by 2D INADEQUATE and 15N NMR. The reaction of enaminones with 3-amino-2-cyanopent-2-enedinitrile can lead to an array of 12 possible products, depending on the reaction pathway and tautomerization. The use of 2D INADEQUATE and (15)N NMR for the unambiguous structure elucidation of the reaction products is discussed in this manuscript.
{"Chemical": ["(15)N", "3-amino-2-cyanopent-2-enedinitrile", "enaminones", "15N"]}