chemical shift. carbon-13 spectra how many c-13 signals? which signals are further upfield? can the...
TRANSCRIPT
![Page 1: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/1.jpg)
Chemical Shift
![Page 2: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/2.jpg)
Carbon-13 Spectra
• How many C-13 signals?
• Which signals are further upfield?
• Can the compounds be differentiated?
OH
O
![Page 3: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/3.jpg)
Correlation Chart
• Same number of signals
• Occur in different areas of spectrum
• Predictable shifts
020406080100120140160180200220PPM
O
020406080100120140160180200220PPM
OH
![Page 4: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/4.jpg)
Chemical Shift Tables
• Complex vs simple• Basics:– Alkane: 5-45ppm– C-Q: 40-70ppm– sp: 70-100ppm– sp2: 100-160 ppm– Carbonyl: 160-220
ppm
![Page 5: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/5.jpg)
Predict C-13 Chemical Shifts
• If carbon fits two categories, choose higher shift
Cl O
O
OH
OH
O
O
![Page 6: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/6.jpg)
More subtle points
• Inductive effects• Additive effects• More substituted
sp3 carbon is further downfield
7.9
35.9
210.8
43.5
31.0
33.8
29.4
20.4
11.6
O
7.9
32.1
207.3
79.2 57.2
O
O
![Page 7: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/7.jpg)
More subtle points
• Carbonyls– Above 200ppm,
ketone and aldehyde
– Below 200ppm, O=C-Q
– Explain by shielding and resonance
O O
OH
O
OH
O
OH
O
![Page 8: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/8.jpg)
More subtle points
• Alkene vs Alkyne
![Page 9: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/9.jpg)
Which Structure(s) Fit?
CDCl3TMSabsent
![Page 10: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/10.jpg)
Which Structure Fits?
![Page 11: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/11.jpg)
C3H8O
![Page 12: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/12.jpg)
Proton NMR Shifts
![Page 13: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/13.jpg)
Basic Correlation Chart
• How many 1H signals?• Shift? Proton NMR Chemical Shift (ppm)
alkane CH3 0.9alkane CH2 1.3alkane CH 1.7X=C-C-H(Ph-C-H orO=C-C-H)
2-3
O-C-HX-C-H
3-4
(sp2) C=C-H 5-6Ph-H 7-8O=C-H 9-10O=C-O-H 10-12O-H, N-H 1-5
O
O
OH
NH
O
![Page 14: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/14.jpg)
Common “exceptions”
• Phenyl protons give one “signal” even if nonequivalent
O
![Page 15: Chemical Shift. Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?](https://reader036.vdocuments.us/reader036/viewer/2022062422/56649e8e5503460f94b91397/html5/thumbnails/15.jpg)
Common “exceptions”• Exchangeable protons are broad and small• Washed away with D2O
012345PPM
OH