What is Woodward Fieser rule for Conjugated dienes?

One set of Woodward–Fieser rules for dienes is outlined in table 1. A diene is either homoannular with both double bonds contained in one ring or heteroannular with two double bonds distributed between two rings. In the compound on the left, the base value is 214 nm (a heteroannular diene).

How are Woodward Fieser rules calculated?

Woodward-Fieser Rules for Calculating the π → π* λmax of Conjugated Carbonyl Compounds. (i) Each exocyclic double bond adds 5 nm. In the example on the right, there are two exo-double bond components: one to ring A and the other to ring B.

What is Homoannular and Heteroannular diene?

a) Homoannular Diene:- Cyclic diene having conjugated double bonds in same ring. b) Heteroannular Diene:- Cyclic diene having conjugated double bonds in different rings.

What is acyclic conjugated diene?

Exocyclic double bond :- double bond in which one of the double bond atom is a part of a ring. E. Double bond extending :– when more double bond are present other than conjugated. Different base value :- Acyclic conjugated diene or Hetero annular conjugated diene has 215 nm wavelength.

When to use Woodward Fieser rules for dienes?

Since the conjugated diene base is relatively non-polar, contribution due to different solvents is very minor and can be ignored in most cases. Woodward-Fieser rules for dienes work well for conjugated systems with less than 4 double bonds in .

How are Woodward-Fieser rules used to calculate λmax?

Woodward-Fieser rules can be extended to calculate the λmax of α,β-unsaturated carbonyl compounds. In a similar manner to Woodward rules for dienes discussed previously, there is base value to which the substituent effects can be added and the λmax can be calculated using the formula:

What are the UV Vis rules for Woodward Fieser?

UV-Vis Lesson 3 – Woodward-Fieser Rules As you look over the rules below, you will notice a striking feature. Making the chromophore more conjugated significantly increases the value of λmax. Greater conjugation leads to a longer λmax. CONJUGATED DIENE CORRELATIONS R2C=CR-CR=CR2

When was the Woodward-Fieser rule first used?

In 1959 Louis Frederick Fieser modified these rules with more experimental data, and the modified rule is known as Woodward-Fieser Rules. It is used to calculate the position and λ max for a given structure by relating the position and degree of substitution of chromophore.