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Advanced Higher Chemistry: Unit 2 - Organic Chemistry > NMR Spectroscopy > Flashcards

NMR Spectroscopy Flashcards

1
Q

What does NMR stand for?

A

Nucleur Magnetic Resonance

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2
Q

What are the nuclei of hydrogen atoms?

A

electrically charged

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3
Q

What can the nuclei of hydrogen atoms be imagined as?

A

spinning on their axes

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4
Q

What do spinning charges create?

A

a magnetic field and act as tiny bar magnets

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5
Q

What will tend to happen if a spinning nucleus is placed in a magnetic field?

A

it will align itself with the field (c.f. swimming downstream)

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6
Q

In order for a spinning charge to align itself against the field, what does it require?

A

energy

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7
Q

What kind of energy state is the hydrogen atom in if it aligns itself with the field?

A

low energy state

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8
Q

What kind of energy state is the hydrogen atom in if it aligns itself against the field?

A

high energy state

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9
Q

What are protons aligned with the field said to be?

A

more stable

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10
Q

What kind of energy is supplied to allow transitions to occur?

A

electromagnetic energy

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11
Q

What does the absoption of energy produce?

A

NMR signal

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12
Q

What is the position of a signal in an NMR spectrum measured from?

A

a reference point

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13
Q

What is used as a reference point in an NMR spectrum?

A

TMS (tetramethyl silane) is added to the sample and the signal from this is taken as zero

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14
Q

What is the signal obtained from any given proton measured in and what is this called?

A

ppm (parts per million) from TMS and is called chemical shift of the proton

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15
Q

What is a signal obtained for?

A

all non-equivalent protons

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16
Q

What does each proton in a different environment show?

A

a different signal

17
Q

What does the number of signals give clue to?

A

the number of different protons in the molecule

18
Q

What is the area under the NMR signal proportional to?

A

the number of protons which contribute to the signal

19
Q

What may each signal consist of?

A

a number of closely packed lines

20
Q

Why can each signal consist of a number of closely packed lines?

A

due to the fact that a signal can be split by the neighbouring (adjacent) protons

21
Q

What is the rule for splitting signals?

A

n adjacent protons will be split a signal into n+1 peaks

Advanced Higher Chemistry: Unit 2 - Organic Chemistry (19 decks)

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