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:

Intraspecific chemical variability of essential oil from leaves of Cupressus atlantica Gaussen, an endemic and endangered coniferous species in Morocco. The composition of essential oils isolated from leaves of 11 natural populations of Cupressus atlantica, an endemic and endangered coniferous species from Morocco, was investigated by GC-MS. In total, 42 essential oil components were identified, accounting for 73.1-97.7% of the total oil. Monoterpene (25.2-84.9%) and sesquiterpene hydrocarbons (12.2-46.8%) were the principal subclasses of compounds, with α-pinene (15-65.4%), germacrene D (5.9-30.5%), δ-3-carene (2-16.6%) and γ-cadinene (1.3-9.8%) as the main constituents. The results of the oil composition were analysed by hierarchical cluster and principal component analysis that established three main groups of essential oils. These oils were differentiated by the content of the major constituents (α-pinene, germacrene D, δ-3-carene and γ-cadinene), geographical location and climatic characteristics.
{"Chemical": ["sesquiterpene hydrocarbons", "Monoterpene", "germacrene D", "\u03b1-pinene", "\u03b3-cadinene", "\u03b4-3-carene"]}