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:

Can the chemical reactivity of an ultimate carcinogen be related to its carcinogenicity? An application to propylene oxide. In this article we report calculations of the activation free energy for a chemical reaction between propylene oxide and DNA, in particular with the guanine at the N7 position. Calculations were performed using Hartree-Fock and MP2 methods in conjunction with flexible basis sets. The effects of solvation were considered using the Langevin dipoles and solvent reaction field methods. The calculated activation free energies are in good agreement with the experimental value of 25.36 kcal/mol. Moreover, the reactivities of a series of ultimate carcinogens of the epoxy type toward DNA are shown to be related to their carcinogenicities. Higher reactivity is generally associated with higher carcinogenicity, although transport properties, reactions with ultimate carcinogen scavengers, and the DNA correction mechanism are also very important. It is very likely that the window of reactivity rather than a high reactivity value is the relevant measure of carcinogenicity, since highly reactive ultimate carcinogens interact with water and proteins before they reach DNA.
{"Chemical": ["guanine", "epoxy", "propylene oxide"]}