OCHM 2 > NMR Spectroscopy > Flashcards

NMR Spectroscopy Flashcards

(67 cards)

Study These Flashcards
1
Q

NMR Spec

A

identifies C-H framework; uses radiation from radiofrequency region (radio waves); uses magnet which subjects sample to hig external magnetic field (Bext)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

2 types of NMR spec

A

1H NMR (proton) and 13C NMR (carbon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Proton NMR

A

determines number and type of H’s in a molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Carbon NMR

A

determines type of carbon atoms in a molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Source of NRG to excite

A

Radiation from radiowaves (long wave length, low frequency, and low NRG)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Changes nucleur spins of elements

A

NRG waves that interact with a molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

2 variables characterize NMR

A

applied magnetic field and frequency of radiation used for resonance (v neded for rez and Bext are proportionally related)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Different isotopes

A

Different activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what a nuclear spin generates (charged partices like protons spin on its axis)

A

small magnetic field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Spin up

A

alpha

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Spin down

A

beta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

2 different states of NRG for a proton

A

low and high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

High NRG state

A

nucleus is aligned opposed to Bext

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Low NRG State

A

nucleus is aligned in same direction as Bext

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

protons in different environments

A

absorb at diff frequencies and are distinguishable by NMR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Spin flip

A

when external NRG source (Hv) matches the NRG diff between these 2 states is applied, NRG will be absorbed causing molecules to spin flip from one orientation to another; nrg diff= low v radiation id radio region; nucleus is in resonance when it absorbs RF radiation and spin flips to a higher state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

NMR tells you

A

number of peaks (signals), integration, location, and shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

number of peaks/signals

A

found from diff types of H in a molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

integration

A

number of Hs in peak; will show as size ratio (integral); may show number at top or bottom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

location

A

types of H the molecule has; tells you about neighboring environments; most EN or downfield is more left and farther away from EN then H+ will not be affected by Bext

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

shape

A

spin splitting pattern (neighboring environment or adjacent atoms); n+1: take # of adj H on next C and add 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

heterotopic/diastereotopic protons

A

chemically distinct protons (diff NMR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Enantrotopic protons

A

distinct protons because theyre next to a stereocenter, are equivalent, and give off 1 NMR (diff NMR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Homotopic proton

A

chemically equivalent protons (1 NMR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Tips when finding peaks and integration
- go up to 3 bonds to find uniques H's - if symmetrical or same group w/ H, the singular H will count as 2 - only immediate (1 away) carrbons will split H's w/ stereochem (next to stereocenter=has stereochem) - all carbons on ring have stereochem
26
NMR absorptions appearances
sharp peaks
27
upfield and downfield
decribes the relative location of signals
28
upfield
right
29
downfield
left
30
electrons shield this
nucleus from Bext
31
the less shielded a nucleus is
the more Bext it feels
32
nucleus has high magnetic field strength
needs more frequency to get resonance
33
protons near EN atoms
protons are deshielded, absorb downfield (bc of base electrons)
34
no electron density
experience more magnetic fields (ppm=high)
35
more electron density
experience less magnetic field (ppm=low)
36
delta
symbol for ppm and common scale of chem shifts
37
Bext
external magnetic field
38
Batom
atom's magnetic field
39
Beff
magnetic effect
40
the more you inc EN atoms in environment
the chem shift will increase (go more downfield)
41
spin-spin splitting
what adjacent atoms look like
42
protons act as magnets (BH)
can be aligned w/ or against applied magnetic fiels (affecting the magnetic field nearby H+ feels)
43
simple patterns
singlet, doublet, triplet, quartet, quintet, sextet
44
singlet (s)
single absorption
45
doublet (d)
signal appearing as 2 peaks; area under curve is 1:1; arises by adj proton that can be aligned w/ or against Bext; H+ feels 2 diff magnetic fields; absorbing at 2 different frequencies
46
triplet (t)
signal appears as 3 peaks; area under 1:2:1; arises by adj H+; that can be w/ or against Bext; H+ feels 3 different magnetic fields (1 smaller than Bext, 1 bigger, and one the same); absorbs at three different frequencies and splits one absorption into 3 (since 1 is w/ and against Bext the middle peak is twice as intense)
47
area under NMR signal
proportional to the # of absorbing H+
48
2 different environment with Hs
will split eachother's peak
49
when 2 sets of adjacent H+ are diff from eachother
the # of peaks in an NMR sig is (n+1)(m+1)
50
checklist for IR + MS determination
1) look if M/Z of M+ peak is odd, there's a nitrogen, 2) look to see if there's a M-18 peak and if there's matching broad, s peak of 3000 on IR (there's OH), 3) look if there's a M+3 peak and check ratio for halogen (Cl or Br), 4) look for strong peaks @ 1650-1750 on IR ( there's a carbonyl)
51
tert-butyl
has integration of 9 (proton NMR)
52
What to look for in proton nmr when looking to see if a reaction happened, and which product
difference in amount of peaks (products), loss of [type, spin splitting pattern] at [location] (reaction), location of double bonds (spin splitting patterns) (product)
53
always broad and singlets
NH and OH
54
Why OH proton does not split the NMR signal of the adjacent proton (why it's a singlet)
it moves rapidly from one molecule to another
55
What Carbon NMR tells you
number of peaks, location, DEPT NMR
56
number of peaks (CNMR)
number of unique carbons
57
Location (CNMR)
position of peaks and type of carbon
58
DEPT NMR
determines number of hydrogen on carbon atom
59
looking for uniqueness
look 2-3 carbon/hydrogens out
60
looking for coupling/splitting
only look at adjacent carbon/hydrogen
61
solvents in CNMR
not part of interpretation
62
no split signal in CNMR
of signals = # of lines in CNMR spec
63
DEBT NMR
distortionless enhancement polarization transfer spec
64
Types of DEPT NMR
90: only CH peaks left and 135: CH peaks left, CH2 peaks invert, and CH3 peaks left
65
CH3 (sp3 C)
very shielded and absorbs upfield
66
sp2 C (double bonds or rings)
absorb downfield
67
carbonyl C
highly deshielded and absorb more downfield than other types (most left)
OCHM 2
flashcards
Decks in class (16)
# Cards
Brainscape helps you reach your goals faster, through stronger study habits.
© 2026 Bold Learning Solutions. Terms and Conditions