回答问题---**Extraction Content:** **Question Stem:** Use the spectroscopic data given to identify compounds A-D in the reaction scheme below. **Reaction Scheme Description:** The scheme shows a series of chemical reactions starting with two reactants: Mo(CO)₆ and a cyclic molecule. The cyclic molecule is shown as a 7-membered ring with four double bonds (conjugated), two sp³ hybridized carbons (one with two hydrogens, one with one hydrogen), and one sp² hybridized carbon (part of a double bond, with one hydrogen). It appears to be cyclohepta-1,3,5-triene, also known as tropylidene or cycloheptatriene. The first step shows Mo(CO)₆ reacting with cycloheptatriene, producing compound A and releasing -3CO. Compound A reacts with [Ph₃C]⁺[PF₆]⁻ to form compound B, releasing -Ph₃CH. Compound B undergoes two reactions: 1. Reacts with NaI to form compound C, releasing -Na[PF₆] and -CO. 2. Reacts with NaOMe to form compound D, releasing -Na[PF₆]. **Spectroscopic Data:** **A** ¹H NMR (ppm): δH 2.5 (1H), 3.1 (1H), 3.6 (2H), 4.9 (2H), 6.1 (2H) IR (cm⁻¹): 1984, 1915, 1887 **B** ¹H NMR (ppm): δH 6.6 (7H) IR (cm⁻¹): 2076, 2028 (broad) **C** ¹H NMR (ppm): δH 5.7 (7H) IR (cm⁻¹): 2011, 1963 **D** ¹H NMR (ppm): δH 3.1 (3H), 4.3 (1H), 4.2 (2H), 5.2 (2H), 5.9 (2H) IR (cm⁻¹): 1996, 1926, 1896