C13: HNMR and CNMR Flashcards
Proton NMR looks at the ____ of the compounds, splitting is by ______ ______
H, adjacent H
C13 NMR looks at ____the influence of splitting by ___ on ____ of the compound
Carbons, H on Carbons
3HC-OH, H around the C are ______ and absorb at a _____ field, H at the end of O is _______ absorbs at a ____ field
deshielded, higher, less shielded, lower
the number of _____ implies how many _______ are present
peaks/signals, different types of protons
the amount of ______ implies the ______ of the molcule
shielding clusters of peaks, structure
the _____ of signals imply ______ are present
intensity, how many protons
the _____ of signals gives information about _____
splitting, nearby protons
chemical shift (ppm or delta)
shift downfield from TMS (Hz)/total spectrometer frequency (MHz)
adding electron-withdrawing groups _____ deshielding
increases
the closer to an electron withdrawing group the _______ the chemical shift
greater
the _______ is proportional to the ________ contributing to that peak, (the _______)
area under the peak, number of hydrogens, number of protons
N + 1 rule: if a signal is split by ________ it will split into _____
N neighboring equivalent protons, N+1 peaks
A multiplet often “leans” upward toward the ______
protons that are causing the splitting.
______ groups do NOT split each other
equivalent groups
ex: (CH3)2-CH-C(=O)-CH3
CH3 do not split each other only split by CH therefore a doublet
the distance between peaks of a multiplet (Hz) is _____
J values, coupling constant
J of free rotating CH-CH
7 Hz
J of cis HC=CH
10 Hz
J of trans HC=C(-H)
15 Hz
J of geminal C=C(-H)H
2 Hz
J of ortho (1,2)
8 Hz
J of meta (1,3)
2 Hz
J of allylic C=C(-H)-C(-H)
6 Hz
N-H appears as ________ in NMR
a broadened signal
C13 sensitivity is ____ by a factor of _____ because C13 resonance frequency is _____
decreased, 100, one fourth that of HNMR
Best practice to run C13 twice ______ decoupling and _____ decoupling
off-resonance, broadband
broadband decoupling
each carbon signal appears as a singlet because splitting has been eliminated; gives you number of non-equivalent C
off-resonance decoupling
allows some splitting
DEPT Spectra of quaternary carbon
0 protons
Normal C13 NMR: single peak
DEPT-90: no peak
DEPT-135: no peak
DEPT Spectra of tertiary carbon
1 protons
Normal C13 NMR: single peak
DEPT-90: single peak
DEPT-135: single peak
DEPT Spectra of secondary carbon
2 protons
Normal C13 NMR: single peak
DEPT-90: no peak
DEPT-135: upside-down single peak
DEPT Spectra of primary carbon
3 protons
Normal C13 NMR: single peak
DEPT-90: no peak
DEPT-135: single peak
