Mass Spectrometry And IR Spectroscopy Flashcards

1
Q

What is mass spectrometry

A

An organic compound loses an electron to form a molecular ion
- occurs in a mass spectrometer

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2
Q

What does a mass spectrometer do

A

Detects the m/z ratio of the molecular ion, and produces a mass spectrum

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3
Q

What is m/z ratio

A

Mass to charge ratio
Gives the Mr of a compound

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4
Q

What is molecular ion, how is it represented

A

The positive ion formed when a molecule loses an electron, represented as M+

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5
Q

How to find Mr from mass spectrum

A
  • identify M+ peak
  • clearest peak furthest to the right
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6
Q

Why is there a smaller peak after the M+, what is it called

A

M+1 peak, one unit after M+ due to 1.1% Carbon existing as Carbon-13

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7
Q

What is fragmentation

A

Mass spectrometer breaks some M+ into smaller fragments (fragment ions) that cause other mass spectrum peaks

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8
Q

“Equation” for fragment ion

A

Molecular ion —> fragment ion + radical

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9
Q

Why don’t radicals show as peaks on the mass spectrum

A

Mass spectrometer only detects +ve ions

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10
Q

3 uses of mass spectrometry

A
  • drug testing in sport
  • MOT emissions testing
  • monitoring air pollution
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11
Q

When can covalent bonds absorb IR radiation

A

When it is at the same frequency as their natural bond frequency

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12
Q

What does absorbing IR radiation do to covalent bonds

A
  • bonds absorb energy causing increased vibration
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13
Q

Environment: where does IR radiation come from

A

Sun

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14
Q

How does IR radiation cause global warming

A
  • earth reemits IR from sun at longer wavelength
  • absorbed by greenhouse gases (its at their natural frequency)
  • vibrating bonds reemit energy as radiation causing inc global temperatures
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15
Q

What has been done about global warming

A

Governments introducing policies promoting use of renewable energy resources

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16
Q

What is infra red spectroscopy

A
  • beam of 200-4000cm^-1 IR passed through sample
  • molecules absorb respective IR frequencies
  • beam of radiation analysed to identify sample by frequency absorbed
17
Q

Where does infra red spectroscopy occur

A

Infra red spectrometer

18
Q

What peak do most organic molecules produce

A

Sharp peak
3000cm^-1
Due to absorbtion of C-H bonds

19
Q

Identifying alcohol IR spec

A

Broad absorbance peak
3200-3550cm^-1
Presence of O-H bond

20
Q

Identifying ketone or aldehyde

A

Strong sharp absorbance peak
1640-1750cm^-1
C=O presence

21
Q

Identifying carboxylic acid

A

Very broad absorbance peak
2500-3300cm^-1
O-H bond presence
(No C-H peak, it’s squashed)
Has a C=O same as ketone/ aldehyde

22
Q

Uses of infrared spectroscopy

A
  • breathalysers
  • monitoring gases causing air pollution