Proton (H) NMR Flashcards
What does NMR spectroscopy stand for?
Nuclear Magnetic Resonance
Oscopy is measuring the difference of energy between a high and low state
What does NMR tell you?
Will tell you the electron environment around H
Shows hydrogen neighbours
Defines the number of H’s in a signal
What does the M is NMR stand for?
External. Snaps the spin states to parallel or anti parallel. Moving with the flow (parallel) is lower energy (alpha). Moving against the flow (anti parallel) is higher energy (beta)
What’s does the R stand for in NMR?
Resonance. Alpha flips to beta and beta flips to alpha.
What are the labels on the NMR Spectrum?
Vertical = abundance Horizontal = ppm & resonance frequency
What nucleis do you see NMR
1H, 13C (See 90% of the time)
19F, 31P, 7O (barely see)
What is electron poor and electron rich?
Downfield (left) is electron poor. Up field (right) is electron rich
What is the scale of NMR?
0-14
What is at 12-14
Carboxillic H (most e- poor) O=C-O-H
What’s at 10-9?
Aldehydes (electron poor) O=C-H
What is at 6-5?
Alkene C=C
What is at 4-3?
Othoxy group. H-C-O
What is at 2?
Ketonics H-C-C=O
What is at 1?
Alkane (super electron rich) H-C-CH2
What is around 7.26ppm?
Chloroform
Iodoform
Bromoform
Fluroform
What are the integration values used for?
To account for all protons in the molecule. Divide the lowest area of each peak value by all values. If not a whole number multiply by a number to get a whole number so when everything is added up it squeaks the correct amount of protons
What does the amount of peaks show you?
N+1. So three peaks means two neighbours. 1 peaks means zero neighbours
What is at 11-12ppm
Phenolic H
What is the coupling saying?
Same doesn’t couple with same. Different couples with different
What is the J-value / J-constant?
A spin spin coupling constant. Measure the distance between the peaks.
How many Hz is 3J, 2J, and 4J
3J = 7Hz 2J = 20Hz 4J = 1-2Hz
If the molecule has symmetry how does it affect the signals?
H atoms that are the same on both sides have the same sigma
How do you use IMP
Only use on proton NMR. Use to interpret NMR.
Integration - count how many protons
Multiplicity - look at neighbours
PPM Value - look at position (ppm)
The bigger the J…
The smaller the Hz
What does 1J show?
C-H
What does 5J mean?
Benzene
How to calculate J Values?
Cross multiply the difference between 0 and 1 in units and Hz and then the space between the peaks.
What does the N in NMR stand for?
Nuclear. Dipole moments. What the molecules split
