Question

Combined Spectroscopy Problem: Determine the structure of the following comp on the IR, 'H & C NMR information given. Draw the bond line structure for ne following compounds based ne structure for full credit. 52.A C1H160 molecule shows a broad IR peak at 3400 cm: absorptions at 3045 and 2 strong absorptions at 1600, 1498 cm '; and 1205 cm! The ratio of carbon-bonded hya its 'H-NMR spectrum is, 6:3:2:2:1:1, with a corresponding signal multiplicity of d, a, a, 4:4 m. It's proton decoupled 13C-NMR spectrum has only 8 signals. Predict the structure and m the multiplicity of each nonequivalent set of hydrogens.

Answer 1

To deduce the structure of any given unknown compound with molecular formula, first step is to determine the Degree of unsaturation (DOU) For the calculation of DOU following formula can be used DOU Number of carbons +1 - (Number of Hydrogens + Number of monovalent atoms (like halogens)- Number of trivalent atoms (like N and P))/2 Oxygens can be ignored while calculating DU For C11H160 the DU is = 11+1- (16 ) / 2 = 12-8 = 4 Hence the unknown compound should have 4 double bonds or 4 rings or a benzene ring in its structure. From the given 1H NMR data, the unknown compound could be 1-(4-isopropylphenyl)ethan-1-ol HO 13C NMR spectral values 1H NMR spectral values 22.8 69.9 OH 1.49 .98 OH5.17 143.3 1-(4-isopropylphenyl)ethan-1-ol Chemical Formula: C11H16O 3 H, doublet 125.7 125.7 2 H, doublet 7.28 7.28 126.3 1 H, quartet 126.3 2 H, doublet 7.19 7.19 147.3 - 1 H, multiplet 33.2 2.86 23.3 1.20 23.3 1.20 8 signals 6 H, doublet In the IR spectrum, peak at 3400 cm1 is due to O-H stretching frequency peaks at 1600, 1498 cm1 are due to C C stretching frequency