2. Provide structures for compounds A-D. Include mechanisms. Spectral data for compound D is provided. Reconcile the data provided with the proposed structure of D. Compound D: PPh3 PhLi A B H3O D C + O=PPh3 IR (neat): 2817 (w), 2717 (w), 1730 (s) cm-1 'H NMR (300 MHz, CDC13): 0.92 (t, 7.0 Hz, 6H), 1.2-2.3 (m, 5H), 9.51 (d, 2.5 Hz, 1H). 13C NMR (75 MHz, CDCl3): 0 11.4, 21.5, 55.0, 205.0. (5 marks)