QUESTION 1 (12 MARKS) a) Arrange the following C-H bonds according to decreasing infrared wavenumber and give reasons for your answer. c-6-H CEC-H (2 marks) b) Three isomers (A, B, and C) with molecular formula C4H;O have the following infrared spectra respectively. Propose the structures of the three isomers and explain how the peaks in the given infrared spectra correspond to your proposed structure. wavelength (am) 3 3.5 4 4.5 5 5.5 6 6.5 7 8 9 10 11 12 14 16 100 60 percent transmittance 40 20 0 4000 3500 3000 2500 1400 1200 1000 800 600 2000 1800 1600 wavenumber (cm) B wavelength (m) 4 4.5 5 5.5 6 6.5 7 8 9 10 11 12 14 16 2.5 100 80 percent transmittance 60 mm 40 20 0 4000 3500 3000 2500 800 600 2000 1800 1600 1400 1200 1000 wavenumber (cm) wavelength (m) 3.5 4 4.5 5 5.5 6 6.5 7 3 2.5 100 8 9 10 11 12 14 16 80 m 60 percent transmittance 40 20 0 4000 3500 3000 2500 800 600 2000 1800 1600 1400 1200 1000 wavenumber (cm) (4 marks) c) A sample of (R)-lactic acid was found to have an optical purity of 25%. How much Rand S isomers are present in the sample? (2 marks) d) Consider the following reaction. H H2CH.c+-CH-CH: CH3 CH2 H/Ni Stereoisomers i. ii. Draw Fischer projection formulas for all the stereoisomers. State whether the isomers are optically active or optically inactive. Determine the absolute configuration at each chiral centre in the stereoisomers. (4 marks)