H-NMR – Chemistry – Flashcards
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Unlock answers| NMR is based on |
| nuclei magnetic moments that can either align with the field or against the magnetic field. |
| what does the alpha state refer to? |
nuclei whose mag moments align with the field.
(alpha= align) |
| what does the beta state refer to? |
nuclei whose mag moments align against the field.
|
| alpha vs beta state who has higher energy |
| beta state |
nmr uses a variable of measurment called______ with units called _____ |
chemical shifts (?) units: parts per million (ppm) |
the chemical shift increases in what direction ,
this is called ____ field |
to the left
(called downfield) |
NMR usually is on what nuclei (2)
does 12C have magnetic moments? |
1H & 13 C
12 C (does not have magnetic moments) |
| what does it mean when it says the proton that is being deshielded? |
dieshieled means: the proton is next to an electronegative atom (which is pulling electron density from the proton) thus deshielding it from its own electron cloud) |
| protons that are being deshielded would appear more to the left or right? |
more to the left. (aka more downfield) |
H-Cl vs H-NH2 would one would appear more to left include why |
H-Cl : more on the LEFT b/c Cl is electrongetive & e- WITHDRAWING = proton dishielded
H-NH2: NH2 is an e-donating group and thus shields the proton
|
| when does splitting or coupling occur? |
| when 2 protons that are in close proximity but are NOT magentically identical. |
CH3 -O- CHCl2 would peak would be taller? |
CH3 peak b/c they are more of these type of protons
(CHCl2 just has 1 proton) |
| formula for determining multiplets |
n+1
n= of H that are 3 bonds away |
| area of each peak is determined by |
| ratio of protons producing each peak |
| any more than 4 peaks is called |
| multiplet |
| give the range for R-CH3 protons |
about 0.9
(most shielded) |
| give the range for alkyl (triple bond) protons |
| 1-3 ppm |
| give the range for alkene (double bond) protons |
| 4-7 ppm |
| give the range for aldehydes (double bond) protons |
| 9 to 10 ppm |
| give the range for carboxylic acid (double bond) protons |
10 to 12
most deshielded |
| give NMR shift for aromatic protons |
| 6-8.5 ppm |
| give NMR shift for alcohol protons |
| 3-5 ppm |
| give NMR range for vinylic |
| 5.5 ppm |
