16.2- MASS SPECTROMETRY Flashcards

1
Q

What is mass spectrometry used to do?

A

measure relative atomic masses of atoms

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2
Q

What is mass spectrometry the main method of?

A

main method for finding relative molecular mass of organic compounds

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3
Q

How do the compounds enter the mass spectrometer?

A

in solution

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4
Q

What happens to the compounds when it enters a mass spectrometer?

A

ionised + positive ions accelerated through instrument as beam of ionised molecules

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5
Q

What happens after the compound is ionised + positive ions accelerated through instrument as beam of ionised molecules in the mass spectrometer?

A

these then fly through instruments towards detector

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6
Q

What is measured of the compound by the mass spectrometer?

A

times of flight

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7
Q

What does the time of flight depend on?

A

mass to charge ratio m/z of ion

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8
Q

What is the output of the mass spectrometer presented as?

A

graph of relative abundance (vertical axis) against mass/charge ratio (horizontal axis)

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9
Q

Why is the horizontal axis (mass/charge ratio) effectively relative mass?

A

as charge on ion normally +1

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10
Q

What is the graph from the mass spectrometer called?

A

mass spectrum

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11
Q

What does mass spectra often show?

A

masses to nearest whole numbers only

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12
Q

What do mass spectrometers that can measure to three or four decimal places be used to do?

A

allow us to work out molecular formula of parent ion

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13
Q

What does high resolution mass spectrometry make us of the fact?

A

makes use of the fact isotopes of atoms don’t have exactly whole number atomic masses (except carbon-12 which is exactly 12 by definition)

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14
Q

What can be used to identify molecular formula from the accurate relative molecular masses from high resolution mass spectrometry?

A

computer database can be used to identify molecular formula from accurate relative molecular mass

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