Cho đến nay các phương pháp phổ học được lựa chọn là: hồng ngoại, tử ngoại, khối lượng và cộng hưởng hạt nhân. Nhiệm vụ của phổ tử ngoại là phát hiện các hệ thống tiếp cách (conjugated), bởi vì sự kích thích các điện tử từ trạng thái cơ bản lên trạng thái kích thích của những hệ thống như thế mới gây nên sự hấp thu trong vùng tử ngoại. Nhưng sự phát triển hiện nay của các kĩ thuật cộng hưởng từ hạt nhân đã đạt đến mức có thể giảm tối đa vai trò của phổ tử ngoại. Hơn nữa, nhiều dao động của nhiều liên kết hoá học không hoạt động trong phổ hồng ngoại, mà hoạt động trong phổ Raman, do đó phổ học Raman được chọn bổ sung cho việc nghiên cứu dao động của các phân tử hữu cơ
Problem C5H10O MW 86 The band at 1716 indicates a carbonyl, probably a ketone The bands at 3000-2850 indicate C-H alkane stretches Problem 1, NMR intrepreted Problem2 C7H14O MW 114 The band at 1718 indicates a carbonyl, probably a ketone The bands at 3000-2850 indicate C-H alkane stretches Prob NMR, interpreted Problem C4H10O MW 74 The broad band at 3339 indicates O-H stretch, probably an alcohol The bands at 3000-2850 indicate C-H alkane stretches The band at 1041 is C-O stretch, consistent with an alcohol Prob NMR, interpreted Problem C6H14O MW 102 The broad band at 3350 indicates O-H stretch, probably an alcohol The bands at 3000-2850 indicate C-H alkane stretches The bands from 1320-1000 indicate C-O stretch, consistent with an alcohol Prob NMR, interpreted Note that the structure has a chiral center and the mixture is racemic Methylene protons adjacent to a chiral center may not be identical Problem C4H8O2 MW 88 Prob 5, IR answer The band at 1743 indicates a carbonyl, probably a saturated aliphatic ester The bands at 3000-2850 indicate C-H alkane stretches The bands in the region 1320-1000 could be due to C-O stretch, consistent with an ester Prob NMR, interpreted Problem C5H10O2 MW 102 Prob 6, IR answer The band at 1740 indicates a carbonyl, probably a saturated aliphatic ester The bands at 3000-2850 indicate C-H alkane stretches The bands in the region 1320-1000 could be due to C-O stretch, consistent with an ester Prob NMR, interpreted Problem C5H10O MW 86 Prob 7, IR answer The band at 1728 indicates a carbonyl, probably an aldehyde; an aldehyde is also suggested by the band at 2719 which is likely the C-H stretch of the H-C=O group The bands at 3000-2850 indicate C-H alkane stretches Prob NMR, interpreted Problem C8H8O MW 120 Prob 8, IR answer The band at 1703 indicates a carbonyl; that the carbonyl is an aldehyde is suggested by the bands at 2828 and 2733 (C-H stretch of the H-C=O group) The bands at 3000-2850 indicate C-H alkane stretches The band (unmarked on the graph below) just to the left of 3000 indicates aromatic C-H stretch Aromatics also show bands in the regions 1600-1585 and 1500-1400 (C-C in-ring stretch), and 900-675 (C-H out-of-plane) Prob NMR, interpreted Note: There are aromatic protons (B, 7-8 ppm), indicating a disubstituted aromatic ring You are not expected to assign the individual peaks in the aromatic region to specific hydrogens on the aromatic ring The aromatic protons show a pattern characteristic of para substitution Problem C9H10O2 MW 150 Prob 9, IR answer The band at 1697 indicates an alpha, beta-unsaturated carbonyl; that the carbonyl is an aldehyde is suggested by the bands at 2828 and 2739 (C-H stretch of the H-C=O group) The bands at 3000-2850 indicate C-H alkane stretches The band (unmarked on the graph below) just to the left of 3000 indicates aromatic C-H stretch Aromatics also show bands in the regions 1600-1585 and 1500-1400 (C-C in-ring stretch), and 900-675 (C-H outof-plane) Prob NMR, interpreted Problem 10 C3H6O2 MW 74 Prob 10, IR answer The band at 1716 indicates a carbonyl The wide band from 3300-2500 is characteristic of the O-H stretch of carboxylic acids The bands at 3000-2850 indicate C-H alkane stretches The bands in the region 1320-1000 indicate the C-O stretch of carboxylic acids Prob 10 NMR, interpreted 2a 300 MHz 1H NMR spectra are shown below for three of the following isomers of dinitrophenol Match each spectrum to the appropriate compound and assign the resonances of the spectrum to the appropriate protons in the compound (12 points) OH OH OH H6 NO2 H6 NO2 H5 NO2 H5 H3 H4 2,3-dinitrophenol NO2 H6 NO2 O2N O2N H3 NO2 H5 H3 H4 2,4-dinitrophenol OH OH H6 O2N 2,6-dinitrophenol NO2 H4 H4 2,5-dinitrophenol H2 3,5-dinitrophenol SPECTRUM A Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) (ppm) SPECTRUM B Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) (ppm) SPECTRUM C Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) X (ppm) X This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use 2b 300 MHz 1H NMR spectra are shown below for 2-methylpyridine, 3-methylpyridine, and 4-methylpyridine Match each spectrum to the appropriate compound and assign the resonances of the spectrum to the appropriate protons in the compound (13 points) H4 H4 H5 H6 N H3 H5 CH3 H6 2-methylpyridine N CH3 CH3 H5 H2 H6 3-methylpyridine H3 N H2 4-methylpyridine SPECTRUM D Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) (ppm) SPECTRUM E Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) (ppm) SPECTRUM F Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) (ppm) This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use 300 MHz 1H NMR and 75 MHz 13C NMR spectra are shown below for the eight constitutional isomers of alcohols with the molecular formula C5H12O Spectra are collected in CDCl3 with tetramethylsilane (TMS) as an internal standard Write the structure and IUPAC name of each alcohol above its spectra (16 points) Hint: First work out the structures of the eight constitutional isomers of alcohols with the molecular formula C5H12O SPECTRUM A Structure: 80 60 40 4.0 3.0 2.0 SPECTRUM B Structure: 80 60 40 4.0 3.0 2.0 SPECTRUM C Structure: 80 60 40 4.0 3.0 2.0 IUPAC name: _ 20 ppm 1.0 ppm IUPAC name: _ 20 ppm 1.0 ppm IUPAC name: _ 20 ppm 1.0 ppm This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use SPECTRUM D Structure: IUPAC name: _ 80 60 40 20 ppm 4.0 3.0 2.0 1.0 ppm SPECTRUM E Structure: 80 60 40 4.0 3.0 2.0 SPECTRUM F Structure: 80 60 40 4.0 3.0 2.0 SPECTRUM G Structure: IUPAC name: _ 20 ppm 1.0 ppm IUPAC name: _ 20 ppm 1.0 ppm IUPAC name: _ 80 60 40 20 ppm 4.0 3.0 2.0 1.0 ppm This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use SPECTRUM H Structure: IUPAC name: _ 80 60 40 20 ppm 4.0 3.0 2.0 1.0 ppm This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use 300 MHz 1H NMR spectra in CDCl3 are shown below for five of the six isomers of dimethylphenol Match each spectrum to the appropriate compound and assign the resonances of the spectrum to the appropriate protons in the compound (15 points) OH H6 H5 OH CH3 H6 CH3 H5 H4 2,3-methylphenol OH CH3 H3 CH3 2,4-methylphenol CH3 H6 H3 CH3 OH OH CH3 CH3 H5 H4 2,5-dimethylphenol H3 H6 OH H2 H5 H6 CH3 H2 CH3 CH3 H4 CH3 H4 2,6-dimethylphenol 3,4-dimethylphenol 3,5-dimethylphenol SPECTRUM A Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) 5X expansion SPECTRUM B Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) 5X expansion This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use SPECTRUM C Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) 5X expansion SPECTRUM D Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) 5X expansion SPECTRUM E Identify the compound (here) _ and label the peaks (below) with the corresponding proton (with labels selected among H2, H3, H4, H5, and H6 as appropriate) 5X expansion This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use 1H NMR spectra are shown below for a single diastereomer of 2-phenyl-1-cyclohexanol (15 points) Ha OH Ph 2-phenyl-1-cyclohexanol Hb OH Ph a Draw cis-2-phenyl-1-cyclohexanol in the most stable chair conformation and draw trans-2phenylcyclohexanol in the most stable chair conformation trans-2-phenyl-1-cyclohexanol cis-2-phenyl-1-cyclohexanol b Name the multiplets (multiplicity and J values) you would expect for Ha and Hb in the cis- and transdiastereomers cis-2-phenyl-1-cyclohexanol Ha _ cis-2-phenyl-1-cyclohexanol Hb _ trans-2-phenyl-1-cyclohexanol Ha _ trans-2-phenyl-1-cyclohexanol Hb _ c Shown below is a 300 MHz 1H NMR spectrum of a single diastereomer of 2-phenyl-1-cyclohexanol in CDCl3 Which stereoismer is it? How you know? 3.6 ppm 10 2.4 ppm 20 40 Hz 10 20 40 Hz This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use The 1H NMR spectrum of (S)-glycidyl benzyl ether (300 MHz in CDCl3, with TMS) is shown below, along with expansions of the resonances at 4.6, 3.7, 3.4, 3.2, 2.8, and 2.6 ppm (20 points) O O (S)-glycidyl benzyl ether ppm 4.6 ppm 3.4 ppm 3.7 ppm 10 20 30 40 Hz 10 20 Hz 10 20 Hz 20 Hz 2.6 ppm 2.8 ppm 3.2 ppm 10 10 20 Hz 10 20 Hz a Assign the resonances at 4.6, 3.7, 3.4, 3.2, 2.8, and 2.6 ppm to the various protons in the molecule, by writing the chemical shift next to the prottons on the diagram below Appendix F from Silverstein is provided at the end of this problem to help you H H H H H H O H O b Describe the multiplets and measure the coupling constants for the resonances at 3.7, 3.4, 2.8, and 2.6 ppm: 3.7 ppm (description and coupling constants): 3.4 ppm (description and coupling constants): 2.8 ppm (description and coupling constants): 2.6 ppm (description and coupling constants): This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use c Explain the appearance of the resonances at 4.6 ppm: d Based on your analysis in sections a–c, write each geminal (2JHH) or vicinal (3JHH) coupling constant on the line by the corresponding arrow Hz Hz Hz H H Hz Hz Hz H H H BnO O Explain the appearance of the resonances at 3.2 ppm Make a splitting diagram to aid in your explanation Use a scale of box is equal to Hz on the horizontal axis and accurately represent the relative heights of the lines on the vertical axis e What differences would you expect between the 1H NMR spectrum of (R)-glycidyl benzyl ether and the 1H NMR spectrum of (S)-glycidyl benzyl ether? f What differences would you expect between the 1H NMR spectrum of racemic glycidyl benzyl ether and the H NMR spectrum of (S)-glycidyl benzyl ether? This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use This work by Dr James S Nowick, Professor of Chemistry, University of California, Irvine, is licensed under a Creative Commons Attribution 4.0 International License Spectra are from Sigma-Aldrich (www.sigmaaldrich.com) under fair use