# How do you use the Woodward Fieser rule?

## How do you use the Woodward Fieser rule?

Woodward’s rules, named after Robert Burns Woodward and also known as Woodward–Fieser rules (for Louis Fieser) are several sets of empirically derived rules which attempt to predict the wavelength of the absorption maximum (λmax) in an ultraviolet–visible spectrum of a given compound.

## How do you calculate max of conjugated organic compounds using Woodward Fieser rule?

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λmax = Base value + ∑substituents- contributes + ∑ other contributes

1. Wood ward fieser rule for conjugated diene and polyenes.
2. For unsaturated carbonyl compound.
3. For aromatic compound or benzoyl compound.

How do you know if your ring is residue in UV spectroscopy?

They can be calculated by using a spectrophotometer. This should be done in the presence of light that falls within the UV region, like 280 nm wavelength. To calculate the quantity of the residue, calculate the value first and then the value of this sample and calculate the difference between the two readings.

How do you calculate maximum absorption?

to get maximum absorption is to reach the absorbance value is 2. equation A = 2-log%T. if your compound get higher absorbance than dilute it as such than you can get the maximum absorbance 2.

### What is λ max?

Lambda max (λmax): The wavelength at which a substance has its strongest photon absorption (highest point along the spectrum’s y-axis).

### What is an Exocyclic?

: situated outside of a ring in a chemical structure.

What is Endocyclic and Exocyclic?

If both carbon atoms connected by a double bond are members of a ring, the double bond is said to be endocyclic; if only one of them is a member of a ring, the double bond is said to be exocyclic.

How do you calculate absorption maxima?

## What is ring residue in UV spectroscopy?

Since both double bonds are cis with respect to substituents making the diene a cisoid diene.  Hence even though the structure has no substituents, the core carbon atoms have yet to be considered as alkyl-substituents. This is known as RING RESIDUE.

## Which compound does not absorb light in the UV visible spectrum?

As a general rule, moleculescontaining conjugated systems of pi electrons absorb light closer to the visible region than saturated molecules or those with isolated double or triple bonds. Ethylene absorbs light of wavelength in the far ultraviolet part of the spectrum, at 180 nm.

Which is an example of the Woodward Fieser rule?

Example of Woodward Fieser rule for Conjugated Dienes and Polyenes 17. Woodward Fieser rule for α,β – unsaturated Carbonyl compounds Woodward-Fieser rules can be extended to calculate the λmax of α,β-unsaturated carbonyl compounds.

What was Wood ward Fieser rule for UV spectroscopy?

Woodward fieser rule :- In 1945 Robert Burns wood ward gave certain rule for correlating λmax with molecular structure. In 1959 Louis Frederick Fieser modified these rules with more experimental data and the modified rule is known as wood ward fischer rule.

### When did Louis Fieser change the Wood ward rule?

In 1945 Robert Burns wood ward gave certain rule for correlating λmax with molecular structure. In 1959 Louis Frederick Fieser modified these rules with more experimental data and the modified rule is known as wood ward fischer rule. According to the wood ward fischer rule the λmax of the molecule can be calculated by using a formula :-

### What is the Wood ward Fieser rule For polyenes?

Wood ward fieser rule for conjugated diene and polyenes. 2. For unsaturated carbonyl compound 3. For aromatic compound or benzoyl compound. 1. Wood ward fieser rule for conjugated diene and polyenes :- A. Homo annular diene : – cyclic diene having conjugated double bond in same ring.