Chapter 7 -modern analytical techniques Flashcards
How does a mass spectrometer work ?
Order !
(6)
1-vaporisation 2-ionisation 3-fragmentation 4-acceleration 5-deflection 6-detection =VIFAAD
What are the two axis on a mass spectrum ?
2
- relative abundance
- mass to charge ratio
What ions does fragmentation favour ?
2
- POSITIVE ions
- with a charge on a secondary or tertiary carbon
What fields are used in mass spectroscopy ?
2
- electric
- magnetic
Where do molecules break up most easily ?
2
- at weak bonds
- or at bonds which give rise to more stable fragments .
What is the molecular ion and where is it found - mass spectrometry?
(3)
- positive ion formed when a molecule loses one electron
- highest m/z ratio
- also relative formula mass
Why is a high vaccination required inside a mass spectrometer ?
(2)
- so unstable ions / fragments can exist and travel freely through electrical , magnetic fields
- air particles would bump with the sample giving wrong results
What is the point of mass spectrometry ?
3
- accurate technique for determining RAM ,
- Relative molecular mass ,
- molecular structure of organic compounds
What is infrared spectroscopy ?
1
- analytical technique used to identify functional groups in organic molecules
Which molecules interact with IR ?
2
- molecules which change polarity as they vibrate
- polar molecules
What is the absorption spectrum a plot of ?
2
- x ( wave number )
- y ( transmittance )
Why are there some broad peaks ?
Carboxylic acid
(2)
- hydrogen bonding
- more extensive in carboxylic acids ( hence broader peak than alcohol )
Why is IR more useful than Boiling point when identifying Compounds and checking purity ?
(3)
- boiling point varies with PRESSURE
- IR spectrum has a distinctive Fingerprint region for compound
- any peaks not found in reference spectrum = impurities
