Block 2 Exam Question Flashcards
What is mass spectrometry?
A technique that determines the mass of individual ions derived from compounds in the gas phase
Limitation of mass spectrometry?
You can’t distinguish between molecules with the same molecular formulae
What does UV-VIS spectrometry identify?
The number of double bonds a molecule has (sigma bonds are transparent)
How does IR spectrometry distinguish between molecules?
Through their functional groups which have absorptions in different regions of the spectrum
Do symmetrical bonds which are symmetrically substituted show absorption in IR?
No (requires a change in dipole moment)
Limitation of IR spectrometry?
Can’t distinguish between molecules with same functional groups
What is C13NMR?
A proton decoupled spectra where each unique carbon will give rise to a different signal
Which carbons have higher delta values in the proton decoupled 13C NMR spectrum?
Those bonded to electronegative substituents (eg O, N, halogen)
In 13C NMR, which type of carbons have a value between 0-90?
sp3 carbons
In 13C NMR, which carbons will have a signal between delta 100-210?
sp2 carbons
Does the 13C NMR signal intensity indicate the number of carbons giving rise to a signal?
No
What is H1 NMR?
When only hydrogens give rise to absorption signals
Which hydrogens in H1 NMR give rise to absorption signals?
Those in different molecular environments
Which H1 NMR molecules show a higher delta value?
Those attached to more electronegative molecules (eg O)
Which type of carbons have a higher delta value in H1 NMR?
Those bonded to sp2 carbons
