UV/Vis Spectroscopy

Woodward-Fieser Rules for Dienes


Woodward-Fieser Rules for Dienes

    Homoannular
(cisoid)
Heteroannular
(transoid)
Parent l=253 nm l=214 nm
=217 (acyclic)
Increments for:
  Double bond extending conjugation 30 30
  Alkyl substituent or ring residue   5   5
  Exocyclic double bond   5   5
Polar groupings:
  -OC(O)CH3   0   0
  -OR   6   6
  -Cl, -Br   5   5
  -NR2 60 60
  -SR 30 30


Example 1:

Transoid:   217 nm
Alkyl groups or ring residues: 3 x 5 = 15 nm
Calculated:   232 nm
Observed:   234 nm

Example 2:

Cisoid:   253 nm
Alkyl groups or ring residues: 2 x 5 = 10 nm
Calculated:   263 nm
Observed:   256 nm

Example 3:

Transoid:   214 nm
Alkyl groups or ring residues: 3 x 5 = 15 nm
Exocyclic double bond:   5 nm
Calculated:   234 nm
Observed:   235 nm

Example 4:

Cisoid:   253 nm
Alkyl groups or ring residues: 4 x 5 = 20 nm
Exocyclic double bond:   5 nm
Calculated:   278 nm
Observed:   275 nm


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