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:

Probing the Mechanism of TBAF-Catalyzed Deacylation of Cellulose Esters. The mechanism of the recently discovered, unusual tetrabutylammonium fluoride (TBAF) deacylation of cellulose esters has been investigated by methods including kinetic isotope effect (KIE) studies. The secondary KIE (kH/kD = 1.26 ± 0.04) measured for deacylation at C-2/3 suggests a mechanism involving a ketene intermediate for those positions. An inverse KIE (kH/kD = 0.87 ± 0.03) for the deacylation at C-6 indicates the involvement of a tetrahedral intermediate in the mechanism. Additional studies suggest the possibility that TBAF chelation by neighboring acyl groups may account for the unexpected regioselectivity at the secondary alcohol esters that is observed in the TBAF deacylation of cellulose esters.
{"Chemical": ["tetrabutylammonium fluoride", "Esters", "TBAF", "acyl", "esters", "secondary alcohol esters"]}