Module 4: Chapter 17 (Spectroscopy) Flashcards
1
Q
What can mass spectrometry do?
A
- identify the molecular mass of an organic compound
2. give further information about the structure
2
Q
How is the molecular mass determined in mass spectrometry?
A
- in the spectrometer the molecule loses an electron to form a positive ion (ion is called the molecular ion)
- m/z ratio detected of the ion and it shows up as the highest mass peak on the spectrum (the molecular ion peak)
- assuming z = 1 its value will be equivalent to the molecular mass of the compound
3
Q
What is fragmentation?
A
- some molecular ions break down into smaller fragments
- two species are formed; a positively charged fragment ion and an uncharged radical
- peak heights reflect the likely hood of the particular fragmentation (the positively charged fragment, no the lost species)
4
Q
What are some applications of mass spectrometry?
A
- all molecule fragment in slightly different ways according to their structure, therefore a compound’s mass spectrum is unique and can be used to identify it (unknown compounds)
- mass spectrometry is amongst the techniques used in sport to test urine samples for banned substances
5
Q
What happens to covalent bonded molecules with IR?
A
- covalent bonds in molecule posses energy and have a natural vibration about a central point
- they can absorb infrared radiation, this makes them vibrate more
- vibrates can be stretches or bends (bends change bond angle)
- only absorbs IR that has the same frequency as the natural frequency of the bond
6
Q
What does the amount that a bond stretches or bends depend on?
A
- the mass of atoms (heavier = slower vibration)
2. the strength of bonds (stronger = faster vibration)
7
Q
wavenumber = …
A
1 / wavelength in cm^3
- wavenumber is directly proportional to frequency
8
Q
What are some applications of IR spectrometry?
A
- used to monitor levels of localised pollution from nitrogen monoxide and hydrocarbons
- IR-based breathalysers measure the ethanol levels in captured breath
