Lecture 7 (NMR, cont.)!!Chem 237 March 3, 2015Preparing NMR Samples Proper Solvent Level What solvent do you use to dissolve sample?Diagram of NMR Spectrometer300 MHz spectrometer 750 MHz spectrometerExamples of Splitting for Common Fragments0.80.80.90.91.01.01.11.11.21.21.31.31.41.41.51.51.61.61.71.71.81.81.91.92.02.02.12.1ppmppm0.80.80.90.91.01.01.11.11.21.21.31.31.41.41.51.51.61.61.71.71.81.81.91.92.02.02.12.1ppmppm1:3:3:1 quartet area = 2 CH21:2:1 triplet area = 3 CH30.80.80.90.91.01.01.11.11.21.21.31.31.41.41.51.51.61.61.71.71.81.81.91.92.02.02.12.1ppmppm0.80.80.90.91.01.01.11.11.21.21.31.31.41.41.51.51.61.61.71.71.81.81.91.92.02.02.12.1ppmppm1:6:15:20:15:6:1 septet area = 1 CH1:1 doublet area = 6 2 x CH30.80.80.90.91.01.01.11.11.21.21.31.31.41.41.51.51.61.61.71.71.81.81.91.92.02.02.12.1ppmppm0.80.80.90.91.01.01.11.11.21.21.31.31.41.41.51.51.61.61.71.71.81.81.91.92.02.02.12.1ppmppm1:3:3:1 quartet area = 1 CH1:1 doublet area = 3 CH31.01.01.21.21.41.41.61.61.81.82.02.02.22.22.42.42.62.62.82.8ppmPutting It All Together...C6H12OWhen given a molecular formula, calculate the ______________________ (DOU) first. This tells you the number of multiple bonds or rings in a structure.DOU =2C + 2 − H + N − X2DOU =2(6) + 2 − 122= 1There is one ring or double bond in the structure!ppmNMR LAB A - Prelab 1. Give the number of degrees of unsaturation (DOU) for each of the following compounds. a. C9H12O b. C6HCl5O c. d. e. NNNNNHNNH2• What is a DOU (Degree of Unsaturation)?• How many rings and double bonds?• Nitrogen and halogens?• Structure – easy to determine• Molecular formula – need to calculate1NMR LAB A - Prelab• Expand structure to show all of the hydrogens• Look for distinct chemical positions – chemical shifts 1. For each of the following compounds, give the number of signals (resonances) that you would expect to find in the 1H NMR spectrum. a. b. c. d. BrOHSHO2NMR LAB A - Prelab• Expand structure to show all of the hydrogens• For each H, count carefully the number of equivalent neighbors• Add 1 to the count to get the multiplicity• For relative integrations - consult the Pascals Triangle1. For each of the following compounds, give the multiplicity (s, d, t, etc.) and the number of protons (relative integrations) for each type of proton indicated. Be sure to give the integration value for the entire set of protons that are of the type indicated. ClabeOOcd3NMR LAB A - Prelab• Use skills enumerated previously1. Assign the given 1H NMR chemical shifts for each of the following compounds to the appropriate sets of protons, as indicated. ClClClabδ 4.0, 5.8 ppmBrcdefδ 1.0, 1.7, 1.8, 4.1 ppmOOghiδ 1.0, 2.3, 3.6 ppm4NMR LAB A - Prelab 1. Many molecular fragments have easily identifiable coupling patterns by 1H NMR. Match the following molecular fragments with the correct spectrum shown below. a. b. c. d. HCCH2H2CCH3H2CCH2HCCH3CH31 2 3 4 5Splitting DiagramsWhat splitting pattern results when coupling constants differ?Jab > JbcJab = JbcSpin-Spin Splitting (Coupling Constants)Number of Intervening Bonds: 2J > 3J > 4J 2J < 30 Hz 3J < 18 Hz 4J < 5 Hz H C HC CH HC CHCHtypically < 1 Hz Aromatic Systems: HHHHHH3J = 6-10 Hz 4J = 1-3 Hz 5J < 1 Hz Bond Length: HHHHHH1.34 Å 1.40 Å 1.42 Å 3J = 11.5 Hz 3J = 8.0 Hz 3J = 6.4 HzSpin-Spin Splitting (Coupling Constants)Alkene Stereochemistry: HHHHH H3Jcis = 7-11 Hz 3Jtrans = 12-18 Hz 2Jgem = 0-3 Hz Dihedral Angle: HHφ=dihedral angleHaxHaxHeqHeqHaxHeqHaxHeqKarplus Correlation 3Jax-ax (180°) = 8-12 Hz 3Jax-eq (60°) = 2-5 Hz 3Jeq-eq (60°) = 2-5 Hz 23002002004004006006008008001000100012001200140014001600160018001800200020002200220024002400Hz270270280280290290-2508.614277.205283.703460460470470480480-2508.614458.632464.790471.531477.552500500520520540540-2508.614488.322494.588501.009507.537514.124521.679528.253534.871541.52412401240125012501260126012701270-2508.6141254.3701260.3161266.288Spin-Spin Coupling (Splitting or Multiplicity)HzH OOisopentyl formateC6H12O2Which hydrogens are responsible for which peaks?abdceaeddccbbaaPutting It All Together...ppm335.985.981.991.99111.01.01.21.21.41.41.61.61.81.82.02.02.22.22.42.42.62.62.82.8ppm-2.0540.9751.0001.0251.0891.1112.4132.4382.4632.4882.5652.5872.6092.6302.6522.6742.695C6H12O DOU = ? 300 MHz1:3:3:1 quartet 2.45 ppm J = 7.5 Hz area = 2 CH21:6:15:20:15:6:1 septet 2.63 ppm J = 6.5 Hz area = 1 CH1:1 doublet 1.1 ppm J = 6.5 Hz area = 6 2 x CH31:2:1 triplet 1.0 ppm J = 7.5 Hz area = 3 CH3Putting It All Together...C6H12O DOU = 1 300 MHz1:3:3:1 quartet 2.45 ppm J = 7.5 Hz area = 2 CH21:1 doublet 1.1 ppm J = 6.5 Hz area = 6 2 x CH31:2:1 triplet 1.0 ppm J = 7.5 Hz area = 3 CH31:6:15:20:15:6:1 septet 2.63 ppm J = 6.5 Hz area = 1 CHPutting It All Together...335.985.981.991.99111.01.01.21.21.41.41.61.61.81.82.02.02.22.22.42.42.62.62.82.8ppm-2.0540.9751.0001.0251.0891.1112.4132.4382.4632.4882.5652.5872.6092.6302.6522.6742.695C6H12O DOU = ? 300 MHzFragment analysis: That takes care of 5 of the 6 carbons. This leaves only 1 carbon, 1 oxygen and ? DOU! The carbon and the oxygen must be…?There is only one way that these fragments can be put together...Interpreting IR Spectra% Transmittance0255075100Wavenumber400760112014801840220025602920328036404000(cm-1)5001000150020003000Typically, only the diagnostic peaks are identified in IR. Fantastic way of checking for the presence of certain functional groups! Example: Is my 1 DOU a carbonyl group?O2-methyl-3-pentanoneC-H stretchesC=O stretchC-C stretches“fingerprint region”Integrated Spectroscopy Problem6. (15 pts) An unknown molecule exhibits a high resolution EI MS exact mass of m/z = 188.1058 (molecular ion). Its IR spectrum shows a strong peak at 1745 cm-1. Its 13C NMR shows 5 peaks. The H NMR spectrum is shown below. Show your work for partial credit.Formula Exact Mass CalcC9H16O4188.1049C9H20N2O2188.1525C11H24O2188.17761H NMRC8H12O5188.0685Another Integrated Spectroscopy Problem5. (15 pts) An unknown molecule exhibits a high resolution EI MS exact mass of m/z = 116.0836 (molecular ion). Its IR, 1H and 13C NMR are shown below. Show the structure that best fits the data. The integrals in the expanded insets are not drawn to scale. Show your work for partial credit.Formula Exact Mass CalcC6H12O2116.0837C7H16O 116.1201C9H8116.14091H NMRC4H4O4116.2392C13 NMR and IR