structure determenation Flashcards
what is the difference between carbon 12 and 13
carbon 12 has no nuclear spin and carbon 13 does
what is resonance
the cycle of excitation and relaxation in an NMR spectrometer
what is chemical shift
the place in the spectera where the nucleus absorbs energy and is related to the difference in frequency between that of the resonating nucleus and TMS
what is TMS defined as in NMR
zero
why is TMS used as zero
as it is unreactive,non-toxic,easy to remove from the sample and gives a sharp strong peak
what will a carbon NMR tell you
The number of different carbon enviroments from the number of different peaks
the type of enviroment using chemical shift
what will a carbon NMR not tell you
the number of carbon atoms responsible for each peak
what do the protons interact with in proton-NMR
the protons interact with radio waves
what is the frequency of the interaction of protons determined by
the frequency of the interaction of protons is determined by the enviroment they are in
what information does a proton NMR give you
number of peaks=number of proton enviroments
chemical shift gives type of proton enviroment
relative peak areas gives proportion of protons in each enviroment
spin-spin coupling gives info about protons on neighbouring carbon atoms
what is coupling
the frequency at which a proton interacts with the radio wave can be influenced by protons on neighbouring carbon atoms
what is the n+1 rule
n hydrogens on an adjacent carbon atom will split into n+1 peaks
what is the ratio of peaks in a triplet
1:2:1
what is the ratio of peaks in a quartet
1:3:3:1
what is double coupling
on middle of the chain carbons
the protons can couple to both of the carbon groups next to it
