Question

The IR and proton NIR spectra of an unknown organic compound, with the molecular formula CaHioO, are shown be Assign the most informative IR peaks, assign the NMR signals, and determine the structure of the unknown. 1Combined IR NMMR probiem ategral valos Dr. Joel Slade Laboratory Exam I March 7, 2019

Answer 1

ANSWER: To propose the structure,follow the below said steps.

• Determine the number of unsaturations with the help of degree of unsaturation calculations.
• Find the possible functional groups with the help of IR spectrum.
• Analyze the NMR spectrum to determine the nature of protons from the given spectra.

Given below is the structure of unknown with proton-NMR assignments.

* Given the molecular formula is CaH100. ※ Degree of unsaturation = [ 2*no. of C's + 2 no. of N's-no. of H's-no. of halogens]/2 = [2*8+2-101/2 = 04 Which suggesting that the compound has ONE BENZENE RING (one ring + three double bonds) * Analysis of the IR & NMR spectral data: SPETCRA Peak position INTERPRETATION Broad peak at 3340 cm-1 Peak at 3050 cm-1 Peaks at 2950, 2840 cm1 Peak at 1600 cm-1 Peak at 1400 cm-1 Peak at 1050 cm-1 Hydroxyl group (O-H stretching vibrations sp2-C-H (C-H stretching vibrations Sp3 -C-H (C-H stretching vibrations Aromatic C-C (C-C stretching vibrations Aliphatic -CH2 (C-H bending vibrations -C-O of primary alcohol (C-0 stretching vibrations IR Peak at ~o 2.00 ppm, broad Should belongs to aliphatic -0H. singlet, 1H Peak at ~6 2.80 ppm, triplet,|Should belongs to -CH2 group which is next to a 2H i.e.)-OH 1H-NMR -CH2 & a phenyl group. i.e.) Ph-CH2-CH2- Peak at ~6 3.80 ppm, triplet, Should belongs to -CH2 next to which is next to 2H a -CH2 & an oxygen atom Should belongs to aromatic protons in ring i.e.) -0-CH2-CH2 Peaks from ~δ 7.50- 7.20ppm, multiplet, 5H (withparticularly to a mono-substituted benzene no clear splitting pattern) i.e.) mono-substituted benzene rin

* Structure and explanation: The above observations confirming that the compound has a mono-substituted aromatic ring with two-CH2 groups and one -OH groups. All these findings confirming the structure as phenylethan-1-ol он 2-phenylethan-1-ol * Proton NMR assignment is shown below. H2 OH Ha; δ 2.00 ppm, singlet, 1H Hb; 3.80 ppm, triplet, 2H Hc; 8 2.80 ppm, triplet, 2H Hd; δ 7.50-7.20 ppm, multiplet, 5H