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Chemistry > Proton NMR > Flashcards

Proton NMR Flashcards

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1
Q

Similarities between proton NMR and carbon 13 NMR

A

One signal for each set of equivalent H or C13 atoms

The closer the atom to a very electronegative atom and/or double bond the greater the chemical shift (to the left)

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2
Q

Differences between proton NMR and carbon 13 NMR

A

Proton NMR has a relative area of signals related to relative number of H atoms whereas carbon has no link
In proton the signal is split by neighbouring H atoms on adjacent carbons whereas carbon 13 has no splitting

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3
Q

Name of molecule you wish to prepare

A

Target molecule

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4
Q

steps to prepare to run a proton NMR spectrum`

A

sample dissolved in solvent

placed in long narrow tube

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5
Q

what does a spectrum proton NMR machine use to find the peaks

A

uses radio waves
in a very strong magnetic field
using superconductive magnets

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6
Q

structures in a proton NMR machine

A

magnet
nitrogen jacket
probe
helium jacket

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7
Q

what does a proton NMR test for in certain atoms

A

nuclear spin

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8
Q

some examples of molecules with nuclear spin

A

13C and 1H

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9
Q

what does a nuclear spin generate

A

a magnetic field

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10
Q

what does the direction of a magnetic field depend on in an atom

A

the direction of spin

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11
Q

does the direction of spin usually have the same or different amount of energy

A

the same

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12
Q

why do different directions of nuclear spin have different energies in a magnetic field

A

one way is opposing the magnetic field

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13
Q

what is the difference in nuclear spin (the energy gap) corresponded to

A

the frequency of radio waves

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14
Q

solvent used for proton NMR

A

CCL4

CDCL3

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15
Q

why are these solvent used for proton NMR

A

free of H atoms

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16
Q

what is the chemical used to calibrate the proton NMR spectrum

A

tetramethylsilane

TMS

17
Q

why is TMS used to calibrate proton NMR

A

its signal is far away from other signals
it only gives one signal
its non-toxic
it is inert
it has a low boiling point so easily removed

18
Q

how many signals for each equivalent set of H atoms it represents in proton NMR

A

1

19
Q

what is the intensity of each signal proportional to

A

the number of equivalent H atoms it represents

20
Q

what does the area of a HNMR peak represent

A

the same area represents the same overall number of H atoms

21
Q

equation for spin-spin coupling in HNMR

A

number of H’s next door + 1

22
Q

name of spin-spin coupling with one peak

A

singlet

23
Q

name of spin-spin coupling with two peaks

A

doublet

24
Q

name of spin-spin coupling with three peaks

A

triplet

25
Q

name of spin-spin coupling with four peaks

A

quartet

26
Q

name of spin-spin coupling with multiple peaks

A

multiplet

27
Q

exceptions to spin-spin coupling in HNMR

A

H’s that are equivalent

H’s that are on O’s

28
Q

what is the spectra recorded on the scale of HNMR

A

chemical shift

29
Q

what does the chemical shift mean in proton NMR

A

how much the field is shifted compared to the field of TMS

30
Q

equation for finding the chemical shift of a peak in HNMR

A

((field for TMS - field measured) / field for TMS) X 10^6

31
Q

units for chemical shift HNMR

A

parts per million

32
Q

what changes the chemical shift of a peak

A

the more electronegative groups around the H the greater the shift

33
Q

what would triplet quartet in ratio 3:2 mean

A

CH3 - CH2 ethyl group

34
Q

what would triplet triplet in the ratio 2:2 mean

A

CH2 - CH2

35
Q

what would a singlet at intensity 3 mean

A

CH3 - methyl group

36
Q

what would a singlet at intensity 1 mean

A

OH - alcohol group

Chemistry (24 decks)

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