Spectroscopy: Pictures of MoleculesPowerPoint PresentationSlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Spectroscopy: Pictures of MoleculesFocus on nmr (nuclear magnetic resonance)h6h5h4h3h2h1+_________  ΔE = h4  ________________ +_________h6h5h3h2h1SPECTROSCOPY AND THE ELECTROMAGNETIC SPECTRUM Hz m nm cm-1 kcal/moleRadiofrequency AM: 106 FM,TV: 108 3x108 106 109 0.01 0.00003_______________________________________________________________microwave ROTATION (radar: 10 GHz, microwave oven 2.45 GHz = 15 cm) <1012 300 3x105 33 0.1_______________________________________________________________far infrared (torsional vibrations) 1013 30 30000 333 1.0_______________________________________________________________infrared VIBRATION (Stretch, bend) 1014 3.0 3000 3333 10Hz m nm cm-1 kcal/molenear infrared 3.8x10140.78 780 12820 36___________________________________________________________ (red)visible (green) VALENCE (blue) ELECTRONIC 8.6x10140.35 350 28150 82 conjugated  systems ____________________________________________________________ultraviolet – single  bonds 1.5x10150.2 200 50000 143___________________________________________________________vacuum ultraviolet -  bonds 3x1015 0.1 100 105 286____________________________________________________________X-rays,  rays Ionization ( 4-24 eV, 100-550 kcal/mol, 286-52 nm)Core electronic (30-50 eV, 700-1200 kcal/mol, 41-24 nm)Nuclei have “spin”: quantum property, but like little rotating magnetsΔE = h/2•B • B = magnetic field in Tesla Earth’s B = 50 Tesla kitchen magnet B = 10 milliTesla nmr magnet = 1.4 – 12 Tesla γ = magnetogyric ratio varies with element, isotope Only isotopes with odd # protons or neutrons) have  non-zero 1H, 13C, 19F, 31P: yes 12C, 16O: noElectromagnetic radiation: ΔE = h 4.7T = 0.02 cal/mole for 1H!  = B •/2CH3CH2OH, 10 MHz, 0.23 TeslaArnold J.T.; Dharmatti, S.S.; Packard, M.E. ; J. Phys. Chem. (1951) 507CH3CH2OH, 60 MHz (ca. 1975) B = 1.4 TSignal at 0 = tetramethylsilane (TMS) Me4Si, internal calibration standardCH3CH2OH, 180 MHz (ca. 1985) B = 4.2 TCH3CH2OH, 300 MHz (ca. 2000) B = 7.0 TWhy higher magnetic field?Chemical shift in  (=ppm downfield from TMS)Chemical Shifts by Functional Group RCH3 0.9 R2CH2 1.3 R3CH 1.8C=C-CH2- 1.5-2.6O=C-CH2- 2.0-2.5 ROH 0.5-5NC-CH2- 2.2 -NH 1-3C6H5CH2- 2.3-2.8 RCO2H 10-13R2NCH2- 2.2-2.9ClCH2- 3.1-4.1BrCH2- 2.7-4.1ICH2- 2.2-4.2 ROCH2- 3.3-3.7RC(=O)OCH2- 3.8-5.0C=CH2 4.6-5.0 C=CHR 5.0-5.7RC(=O)H 9-10C6H5-H 6.5-8.5CC-H 1.8-3.1X-CH2-Y:≈ (X-1) + (Y-1) = X+ Y - 22H2H3HDistance from functional group decreases Number of Hs for that signal  area under peak (“the integral”)Coupling of adjacent H’s signals (“splitting”) H-C-C-H “N+1” ruleSpin of adjacent nuclei affect local B: CH3CH2Br2 H next to 3 H: quartet next to triplet6 H next to 1 H: septet (multiplet) next to doublet1 H next to 1 H: doublet next to doublet1 H next to 3 H: quartet (3+1) next to doublet (1+1)tBu: 9 H singlet, ca. 1.0Ph-: 5 H singlet/multiplet  6-8 (multiplet if lone pair or  system on benzylic atom)2H2H3HSplitting from both sides4H2HIdentical Hs give identical (superimposed) signalsLeaning of peaks towards what they are coupled to/split byRing Current: downfield (deshielded) shiftRing Current: upfield (more shielded) shift[18]Annulene: Outer Hs:  9.3 Inner Hs:  -3.0Dynamic nmr:“shutter speed” of technique-OH, -NH- usually don’t split adjacent CH and vice versa. Also much broader than CH.Exchange rate of OH by H bonding faster than nmr time scale.Solvents: 99% of signalH-free: CCl4Deuterated: CDCl3, CD3COCD3, C6D6|VC8H9NO22H 2H 2H 3HC7H14O22H 9H 3H13C nmrIf 1H nmr (0-10 ) = 10 feet on screen,Then:0 Hz = Nashville13C nmr = 55 feet (250 ) wide in Cookeville13C Chemical Shifts ()by Functional GroupRCH3 0-35 R2NCH2- 35-50R2CH2 15-40 ClCH2- 25-50R3CH 25-50 BrCH2- 20-40 R4C 30-40 ROCH2- 50-65C≡C 65-90C=C 100-150 RC≡N 110-125Aromatic 110-175RCO2R 160-185RCH=O 190-220 R3SiCH30R2C=O 190-220 CHCl378(triplet)Magnetic Resonance Imaging (MRI)-Spatial resolution (like CT scan vs. X-ray)- not frequency resolved spectra, but rather relaxation rate of excited H nuclei over time. Rarer nuclei (31P) give some structural data (ATP vs.