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:

Prenatal developmental toxicity studies on diundecyl and ditridecyl phthalates in Sprague-Dawley rats. This study evaluates the developmental toxicity of two high molecular weight dialkyl phthalate esters, diundecyl phthalate (DUDP) and ditridecyl phthalate (DTDP). Sprague-Dawley rats were administered 0, 0.25, 0.50, or 1g/kg/day of DUDP or DTDP, by gavage, on gestation days 6-20. DUDP and DTDP had no adverse effects on maternal body weight and food consumption. The number of live fetuses, percent of post-implantation loss and of resorptions, fetal sex, and fetal body weights were not affected by either phthalate. There was no evidence of teratogenicity, whatever treatment. Small decreases in the anogenital distance of male fetuses were noted at 0.5 and 1g DUDP/kg/day. The incidence of fetuses with supernumerary lumbar ribs was significantly higher than control at 0.5 and 1g DUDP/kg/day. Thus, DTDP was not developmentally toxic up to 1g/kg/day and there were signs of DUDP-induced fetal effects at 0.5 and 1g/kg/day.
{"Chemical": ["DUDP", "dialkyl phthalate esters", "DTDP", "phthalate", "ditridecyl phthalate", "diundecyl phthalate", "diundecyl and ditridecyl phthalates"]}