Identify the compound:\nWhich structural formula correctly represents tricresyl phosphate (TCP), an aryl phosphate triester?

Introduction / Context:
Tricresyl phosphate (TCP) is an organophosphate used historically as a plasticizer and flame retardant (with safety considerations). Recognizing its structural representation helps distinguish organic phosphate esters from inorganic phosphates and fertiliser salts often encountered in process and agricultural chemistry contexts.

Given Data / Assumptions:

• TCP is a triaryl phosphate ester derived from cresols (methylphenols) and phosphoric acid.
• It contains three cresyl (CH3–C6H4–O–) groups bound to phosphorus via oxygen.
• In shorthand, it is written as (CH3C6H4O)3PO or (C7H7O)3PO, overall formula C21H21O4P.

Concept / Approach:
A phosphate triester has the general form OP(OR)3, where R is an organic group. For tricresyl phosphate, R is cresyl. In contrast, options listing inorganic salts (ammonium phosphates, potassium phosphate) or minerals (fluorapatite) are unrelated to an organophosphate ester structure and are common fertiliser or mineral forms, not plasticizers.

Step-by-Step Solution:

Verification / Alternative check:
Material safety data and chemical catalogs show TCP as C21H21O4P; structural depictions confirm three aryl–O–P linkages around a phosphoryl center.

Why Other Options Are Wrong:

• Fluorapatite (b) is a phosphate mineral used in fertiliser manufacture.
• (c) and (d) are inorganic ammonium phosphates used as fertilisers.
• (e) is an inorganic salt, not an organic ester.

Common Pitfalls:
Assuming any “phosphate” name implies inorganic salt; overlooking organic phosphate esters in industrial chemistry.

Final Answer:
(CH3C6H4O)3PO (commonly written as (C7H7O)3PO)