1. Other Magnetic Nuclei than 1 H 2 H (Deuterium): I = 1; simplifies proton spectrum as H-D coupling is small X-CH 2 -CH 2 -CH 2 -COYX-CH 2 -CH 2 -CD 2 -COY triplet, quintet, triplettriplet, slightly broad triplet 31 P: I = 1/2 (100% natural abundance) large coupling constants P-H = 200-700 Hz 19 F: I = 1/2 (100% natural abundance) coupling constants F-CH = 50-100 Hz 29 Si: I = 1/2 (100% Natural abundance) Si-CH coupling constant is about 6 Hz; only low intensity (satellites) 13 C: I = 1/2 (1.1% Natural abundance) C-H coupling (about 100-200 Hz) is not seen unless enriched with 13 C

2. Fluoroacetone, CH 3 COCH 2 F 19 F,H coupling ( I = ½) 2J2J 4J4J

3. 13 C-NMR Spectroscopy 12 C not magnetically active but 13 C has I = ½; its natural abundance is 1.1%; The sensitivity of 13 C is only 1/5700 of 1 H; this sensitivity problem is overcome with Fourier Transform (FT) NMR instrumentation (1970’s); Usually, the peak splitting due to couplings with protons are removed by broadband decoupling in a double resonance experiment; broadband decoupling can also enhance the 13 C signal intensity caused by the Nuclear Overhauser Effect (NOE) 13 C chemical shifts are reported relative to TMS; 300 MHz for 1 H-NMR = 75.5 MHz for 13 C-NMR; 10 mg in 0.5 mL of solvent in 5 mm tube

4. Double Resonance: Spin-Spin Decoupling triplet - sextet - triplet irradiate triplet - quartet irradiate singlet - singlet irradiate triplet - triplet Protons can be readily decoupled if they are about 100 Hz apart

5. 13 C-NMR of diethylphthalate proton coupled

6. 13 C{ 1 H} NMR of diethylphthalate proton decoupled why low intensity?

7. 13 C{ 1 H}-NMR of diethylphthalate Proton decoupled 10-s delay

8. Peak Intensities in 13 C-NMR the relaxation times in 13 C-NMR vary over a wide range so peak areas do not integrate for the correct number of nuclei; long delays would work but the time required is prohibitive; NOE response is not uniform for all C atom environments; C atoms without protons attached give low intensity; substitution of D for H results in decreased intensity; deuterium has I = 1 so 13 C is split into 3 lines ratio 1:1:1 when coupled to one deuterium (possible spin states for D are -1, 0, +1) thus CDCl 3 exhibits a 1:1:1 triplet in 13 C-NMR

9. Chemical Shifts in 13 C-NMR Carbon chemical shifts parallel (generally) proton shifts but with a much broader range 12 44 36 46 Number of different aromatic 13 C resonances in substituted benzene molecules

10. Diamagnetic shielding (electrons in s- and p-orbitals) and paramagnetic shielding (electrons in p-orbitals with angular momentum) contributes to the shift of C- atoms. 13 C shifts of functional groups

11. Well defined for acyclic, saturated hydrocarbons  = -2.5 + ∑A i n i  Methane = -2.1 replacement of H by C (CH 3, CH 2, CH, C) causes a +9.1 shift in the  -position, +9.4 in the  -position, and -2.5 in the  -position. Replacement of hydrogen causes a relative constant shift that depends primarily on the electronegativity of X. Calculation of 13 C shifts

12. Well defined for acyclic, saturated hydrocarbons  = -2.5 + ∑A i n i

15. t-butyl alcohol

16. 2,2,4-trimethyl-1,3-pentanediol