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:

High-Accuracy Estimates for the Vinylidene-Acetylene Isomerization Energy and the Ground State Rotational Constants of :C=CH2. Highly accurate calculations are reported for properties of vinylidene (H2C=C:), specically the position of its zero-point vibrational level relative to that of acetylene and its equilibrium structure and ground state rotational constants. The isomerization energy of vinylidene calculated at the HEAT-456QP level of theory is 45.530.15 kcal mol1, in agreement with the previous best estimate, but associated with a much smaller uncertainty. In addition, the thermochemical calculations presented here also allow a determination of the :C=CH2 bond energy of the vinyl radical at the HEAT-345(Q) level of theory, which is 77.70.3 kcal mol1. The equilibrium structure of vinylidene, estimated with an additivity scheme that includes treatment of correlation eects beyond CCSD(T) as well as relativistic and adiabatic (diagonal Born-Oppenheimer correction) contributions is rCC=1.29820.0003 A; rCH=1.08440.0003 A; and CCH=120.050.05o, with zero-point rotational constants (including vibrational contributions and electronic contributions to the moment of inertia) estimated to be A0 = 9.49250.0150 cm1; B0 = 1.32170.0017 cm1 and C0 = 1.16020.0016 cm1. INTRODUCTION.
{"Chemical": ["vinylidene", "Acetylene", "acetylene", "CCH", "vinyl", "H2C=C:", "Vinylidene", ":C=CH2"]}