IR Spectroscopy Flashcards
If you have a broad peak >3000
what functional group would cause this?
O-H
Broader signal indicate intermolecular hydrogen bonding (diluting the conc of OH will result in a less braod peak)
If you have a sharp peak >3000
What functional group would cause this?
N-H
(often one band indicated R₂NH, two bands RNH₂)
What would a razor sharp peak around 3300 indicate
C-H triple bond
sp hybridisation
What would a weak peak around >3000 indicate
sp² hybridised C-H
What would a medium peak around <3000 indicate?
sp³ hybridised C-H
What two functional groups may appear around 2200 cm⁻¹
C-N triple bond
C-C triplet bond
What functional group would appear around 1800cm⁻¹
acid chlorides
(inductive effect strengthens C=O)
What functional group would appear around 1800+1790cm⁻¹
anhydrides
(inductive effect strengthens C=O)
What functional group would appear around 1735cm⁻¹
esters
(inductive effect strengthens C=O)
What functional group will appear around 1700cm⁻¹
Aldehydes or Ketones
(cyclic ketones show higher frequencies - especially the bigger the ring strain)
What functional group will appear around 1690cm⁻¹
aryl ketones
(Resonances weaken C=O because electron density is pushed back onto oxygen from carbonyl)
Weak affect however because the aromaticity is lost
What functional group will appear around 1680cm⁻¹
enones
(resonance weakens C=O)
What functional group will appear around 1660cm⁻¹
Amides
(resonance weakens C=O)
What functional group will appear around 1650-1550cm⁻¹
C=N or C=C
What functional group will produce two peaks around 1500 and 1350cm⁻¹
N=O
