1. Below are given structures of three pairs of compounds. IR, H NMR, or 13C NMR of only one compound per pair is shown. In the boxes provided next to the spectral data, please circle the ompound which matches the spectra shown and briefly justify your choice. Label the reporter peaks or bands on IR. Note: ABLSOLUTELY NO CREDIT WILL BE GIVEN WITHOUT THE WORK SHOWN (18 pt). O O Choose the compound: A / B Justify: O O B A 220 O 200 O 180 160 140 120 PPM 100 80 60 40 20 0 Choose the compound: C / D Justify: OH O D C 7 6 5 4 PPM 3 2 1 0 Choose the compound: E/ F Justify: O OH O O E F 1 2. For the following pairs of isomers, use the suggested spectroscopic technique to distinguish between the structures. Be specific and justify your choice by identifying both compounds using the technique chosen (12 pt). H NMR: O O O B A 13C O NMR: NH2 HN C D O O IR: H2N H2N NO2 E F Scratch paper area: 2 3. For the structures below, identify the ‘reporter’ peak or band on 1H NMR/13C NMR/IR that would allow you to easily distinguish its spectra. Specify the type of multiplicity of the peak (splitting pattern), chemical shift (1H NMR), chemical shift and splitting pattern on H-coupled 13C NMR, and the wavenumber of the band on IR (30 pt). 1 Compound H NMR 13 C NMR IR O O O O OCH3 O F3C O N C H2N 4. NH2 Refer to the structure below to answer the following questions (15 pt). In the box below, draw a 3 coupling tree for proton A. Specify the type of coupling (J), approximate magnitude (Hz), and the splitting pattern for the signal (6 pt). E CH3 NH A H H B H C O O CH3 D Question Answer How many types of different protons are present in this compound How many different alkyl groups are in this compound What is the coupling constant magnitude between protons A and B What is the multiplicity (splitting pattern) of the signal B What type of coupling is between protons A and B What is the chemical shift of proton D How many signals will you see in aromatic region on 13C NMR What is the multiplicity of the carbon on group E on H-coupled 13C NMR Which carbon is the most deshielded (label) How many signals will you see on 13C NMR Which alkyl group is the most shielded What is the approximate stretching frequency of carbonyl bond on IR What is the splitting pattern (multiplicity) of proton C Approximate the chemical shift of the most shielded proton Is the C=O bond in this compound shorter or longer than you would expect for this type of a carbonyl bond 4 The following three problems are designated to test your skills on solving spectral problems. For each problem, determine the IHD (1 pt) deduce its structure (15 pt) from the IR, 1H NMR, and 13C NMR spectra given on the next page. You MUST provide all the relevant information (peak assignments) to get maximum credit. IR: assign all recognizable IR stretch frequencies (4 pt). 1 H NMR: Draw structure on the spectrum and label all non-symmetrically related H’s on the structure (e.g. with a,b,c, etc). Then match the labels with the corresponding peaks. (5 pt). 13 C NMR: Draw structure on the spectrum and label all non-symmetrically related C’s on the structure (e.g. with a,b,c, etc). Then match the labels with the corresponding peaks. (5 pt). An unknown unsaturated ether has molecular mass of 86 g/mol. Molecular formula (2 pt): ____________________ Degree of Unsaturation (IHD) (1 pt):__________ Draw the structure of the compound in the box provided below: 7 6 5 10.2 140 4 9.9 10.0 120 100 PPM 20.3 80 3 2 0 31.1 20.9 PPM 1 60 40 20 0 5 6. Molecular formula of an unknown compound is C10H15N. Determine the IHD, deduce the structure and draw it in the box provided below. Degree of unsaturation IHD (1 pt): 8 7 6 5 4 PPM 3 6.3 9.6 2 12.8 1 0 19.9 Note: splitting patterns for proton-coupled 13C NMR are given on top of the decoupled peaks. s 140 s d q t d 120 100 80 PPM 60 40 20 0 6 7. Molecular formula of an unknown compound is C10H10O4. Its IR displays two very strong bands at 1850 and 1740 cm-1, and also stretches at 1000-1200 cm-1 region. The 1H NMR of the unknown shows the following signals: doublet: 7.85 ppm doublet: 7.34 ppm singlet: 3.8 ppm singlet: 2.5 ppm 13 C NMR of the unknown is provided below: 180 160 140 120 100 PPM 80 60 40 20 0 Based on the data provided, determine the IHD of the unknown and deduce the structure. Draw the structure in the box provided. IHD (1 pt): ___________________ 7