C13: HNMR and CNMR Flashcards

1
Q

Proton NMR looks at the ____ of the compounds, splitting is by ______ ______

A

H, adjacent H

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2
Q

C13 NMR looks at ____the influence of splitting by ___ on ____ of the compound

A

Carbons, H on Carbons

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3
Q

3HC-OH, H around the C are ______ and absorb at a _____ field, H at the end of O is _______ absorbs at a ____ field

A

deshielded, higher, less shielded, lower

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4
Q

the number of _____ implies how many _______ are present

A

peaks/signals, different types of protons

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5
Q

the amount of ______ implies the ______ of the molcule

A

shielding clusters of peaks, structure

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6
Q

the _____ of signals imply ______ are present

A

intensity, how many protons

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7
Q

the _____ of signals gives information about _____

A

splitting, nearby protons

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8
Q

chemical shift (ppm or delta)

A

shift downfield from TMS (Hz)/total spectrometer frequency (MHz)

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9
Q

adding electron-withdrawing groups _____ deshielding

A

increases

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10
Q

the closer to an electron withdrawing group the _______ the chemical shift

A

greater

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11
Q

the _______ is proportional to the ________ contributing to that peak, (the _______)

A

area under the peak, number of hydrogens, number of protons

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12
Q

N + 1 rule: if a signal is split by ________ it will split into _____

A

N neighboring equivalent protons, N+1 peaks

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13
Q

A multiplet often “leans” upward toward the ______

A

protons that are causing the splitting.

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14
Q

______ groups do NOT split each other

A

equivalent groups
ex: (CH3)2-CH-C(=O)-CH3
CH3 do not split each other only split by CH therefore a doublet

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15
Q

the distance between peaks of a multiplet (Hz) is _____

A

J values, coupling constant

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16
Q

J of free rotating CH-CH

A

7 Hz

17
Q

J of cis HC=CH

A

10 Hz

18
Q

J of trans HC=C(-H)

A

15 Hz

19
Q

J of geminal C=C(-H)H

A

2 Hz

20
Q

J of ortho (1,2)

A

8 Hz

21
Q

J of meta (1,3)

A

2 Hz

22
Q

J of allylic C=C(-H)-C(-H)

A

6 Hz

23
Q

N-H appears as ________ in NMR

A

a broadened signal

24
Q

C13 sensitivity is ____ by a factor of _____ because C13 resonance frequency is _____

A

decreased, 100, one fourth that of HNMR

25
Q

Best practice to run C13 twice ______ decoupling and _____ decoupling

A

off-resonance, broadband

26
Q

broadband decoupling

A

each carbon signal appears as a singlet because splitting has been eliminated; gives you number of non-equivalent C

27
Q

off-resonance decoupling

A

allows some splitting

28
Q

DEPT Spectra of quaternary carbon

A

0 protons
Normal C13 NMR: single peak
DEPT-90: no peak
DEPT-135: no peak

29
Q

DEPT Spectra of tertiary carbon

A

1 protons
Normal C13 NMR: single peak
DEPT-90: single peak
DEPT-135: single peak

30
Q

DEPT Spectra of secondary carbon

A

2 protons
Normal C13 NMR: single peak
DEPT-90: no peak
DEPT-135: upside-down single peak

31
Q

DEPT Spectra of primary carbon

A

3 protons
Normal C13 NMR: single peak
DEPT-90: no peak
DEPT-135: single peak