Mass Spec + NMR Flashcards
State and explain the steps (4) of mass spectrometry
- ionisation: gaseous atoms ionised by electron gun (1+)
- acceleration: ions accelerated by electric field as they are charged
- deflection: charged particles deflected by electric field
- detection: by electric or photographic methods
How to calculate relative atomic mass (Ar)
[(mass x %) + (mass x %) + (mass x %)] / sum of masses
Which peak on a MS graph shows M+ (molecule ion)
furthest to the right
What peaks in an MS graph show the most stable species
the tallest
Name the 2 types of fragmentation
Heterolytic fission and homolytic fission
Heterolytic fission
fragmentation that leads to the formation of two oppositely charged species
Homolytic fission
fragmentation that leads to the formation of to radical species
Radical
reactive species with an unpaired electron
What species have the least amount of fragmentation
aromatic rings, cycloalkanes
What species have the most amount of fragmentation
alkanes, alcohols, carbonyls
Alcohol fragmentation rules
- C-C bond next to OH group breaks
- loss of H2O may occur (-18)
Alkane fragmentation rule
loss of CH2 units only (-14)
Aldehyde fragmentation rule
- loss of CHO (-29)
ketone fragmentation rule
- loss of group other side of carbonyl
What is used as the reference in NMR
tetramethylsilane (TMS)
what does splitting indicate
number of neighbouring H
singlet H1 NMR
no neighbouring H
doublet H1 NMR
1 neighbouring H
triplet H1 NMR
2 neighbouring H
quartet H1 NMR
3 neighbouring H
quintet H1 NMR
4 neighbouring H
multiplet H1 NMR
5+ neighbouring H
What info does NMR provide about organic molecule structures
- number of signals
- position of signals
- intensity of signals
- splitting pattern
Broadband proton decoupled (BB)
H atoms bonded to C13 can cause splitting so they are decoupled
