1. Spectroscopy Flashcards
what happens in Mass spectroscopy
high energy e- beam bombards molecule
e- is expelled and radical cation is formed
what is the process of forming radical cations called in mass spectroscopy
fragmentation
what is the graph of mass spectroscopy
relative ion abundance plotted
(m/z)
what has the highest m/z in mass spect
what does the heaviest mass correspond to
the parent ion M+.
heaviest mass corresponds to molar mass
what is the limitation of mass spect
cant distinguish between isomers as they have the same molecular formula
cant distinguish between molecular formulas with the same integer mass
what happens in IR spect
IR radiation absorption when radiation frequency exactly matches bond vibration frequency
how is IR spect graphed
% transmittance over wave number (cm-1) graph
what are the pros of IR spect
identifies functional groups
no 2 compounds have identical spectras
what happens in UV vis spect
energy raises e- in molecule with pi bonds from low energy bond (non bonding) to higher energy antibonding molecular orbit
what does UV vis spect identify
conjugated C=C system displays different absorptions than non conjugated
what is a conjugated system
only if one single bond between double bonds
how is UV vis spec graphed
absorbance against radiation wavelength
where is the max absorption in UV vis
at wavelength max
where abouts or what range is C=C showing up on the graph in UV vis spect
170nm
where abouts or what range is C=O showing up on the graph in UV vis spect
170 and 280 nm
what is beer lamberts law
absorbance = log10(I0/I)
A = Ebc
I0 = incident light
I = transmitted light
what is seen in NMR for unique Cs
each unique C = a different signal
if a molecule is symmetrical how many signals are shown in NMR
1
what do C-O/N/halogen (electronegative) do to the delta value for NMR
increases it
what range does sp3 C show up in for NMR
80-90
what range does sp2 C show up in for NMR
100-120
does signal intensity correlate to # of C
no
what do the # of absorption signals correspond to for NMR H
number of different H environments
what are the delta values for electronegative and C=C in NMR H and why
higher as its deshielded
what does the relative area under the number of absorption signals mean
signal area proportional to # H giving rise to the signals
if total # area doesnt = #H in molecular formula then multiply each # by integer
what is the splitting pattern and what does it show for NMR H
occurs when the C atom that Hs bond to is attached to other Hs - vicinal Hs
absorption signals split into N+1 lines
