ORGANIC CHEMISTRY Chapter g 9.10 Carbon-13 NMR Spectroscopy Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.10 Carbon-13 NMR Spectroscopy
ORGANIC CHEMISTRY Chapter g 9. 10A Interpretation of C NMR Spectra o These spectra are often called carbon magnetic resonance(CMr) spectra or C NMR spectra o In some important ways 3C spectra are usually les complex and easier to interpret than proton(h NMr spectr 13CNMR (ppm) Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.10A Interpretation of 13C NMR Spectra These spectra are often called carbon magnetic resonance (CMR) spectra or 13C NMR spectra. In some important ways 13C spectra are usually les complex and easier to interpret than proton (1H) NMR spectra
ORGANIC CHEMISTRY Chapter g Certain differences and similarities of H-NMR and C-nMr o C has only about 1. 1% natural abundance(of carbon atoms) o 2C does not exhibit NMR behaviour(nuclear spinI=0) o as a result 3c is about 400 times less sensitive than h nucleus to the nmr phenomena o due to low abundance we do not usually see 13C-13C coupling o Chemical shift range is normally 0 to 220 ppm Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 Certain differences and similarities of H-NMR and C-NMR 13C has only about 1.1% natural abundance (of carbon atoms) 12C does not exhibit NMR behaviour (nuclear spin, I = 0) As a result, 13C is about 400 times less sensitive than H nucleus to the NMR phenomena Due to low abundance, we do not usually see 13C-13C coupling Chemical shift range is normally 0 to 220 ppm
ORGANIC CHEMISTRY Chapter g o Chemical shifts measured with respect to tetramethylsilane, (CH)Si(i.e. TMS) Similar factors affect the chemical shifts in 3c as seen for h nmr Normal"IC spectra are "broadband, proton decoupled"so the peaks show as single lines o Number of peaks indicates the number of types ofc Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 Chemical shifts measured with respect to tetramethylsilane, (CH3)4Si (i.e. TMS) Similar factors affect the chemical shifts in 13C as seen for H NMR "Normal" 13C spectra are "broadband, proton decoupled" so the peaks show as single lines Number of peaks indicates the number of types of C
ORGANIC CHEMISTRY Chapter g 9. 10B One Peak for Each Unique Carbon atom o Each unique carbon atom in an ordinary organic molecule produces only one C NMR peak 9 Ihere is no carbon-carbon coupling that causes splitting of signals into multiple peaks h attached to carbon can split C NMR signals into multiple peaks o A 3C NMR Spectrum that has the proton interactions eliminated is said to be broadband (BB)proton decoupled Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.10B One Peak for Each Unique Carbon Atom Each unique carbon atom in an ordinary organic molecule produces only one 13C NMR peak. There is no carbon-carbon coupling that causes splitting of signals into multiple peaks. H attached to carbon can split 13C NMR signals into multiple peaks. A 13C NMR spectrum that has the proton interactions eliminated is said to be broadband (BB) proton decoupled
ORGANIC CHEMISTRY Chapter g 9.10C 13C Chemical Shifts =CCECC C=O 0=C-X Ar C C-O 220200180160140120100806040200 ppm Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.10C 13C Chemical Shifts
ORGANIC CHEMISTRY Chapter g CHs COCH2CH3 Ethyl ethanoate has 4 types of carhon so 4 peaker The most obvious peaks are the ester carbond at 19Uppm and the deshielded CH-aitached to 0 at about 7U ppm. 22020018016014012010080604020 Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9
ORGANIC CHEMISTRY Chapter g 10 PPM Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9
ORGANIC CHEMISTRY Chapter g Acetophenone has 6 types of carhon so 6 peaks, with the 4 types of aromatic carbons between 123-140ppm, the ketone carbom at 190ppm and the methd group at 2ppm 200180160140120 100 80 40 20 0 Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9
ORGANIC CHEMISTRY Chapter g 9.10D Off-Resonance Decoupled petra o The off-resonance spectrum tells how many hydrogen atoms are attached to each unique carbon(quartet=3, triplet=2, doublet= singlet=none) Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.10D Off-Resonance Decoupled Spectra The off-resonance spectrum tells how many hydrogen atoms are attached to each unique carbon (quartet=3, triplet=2, doublet=1, singlet=none)