5 Nov woodward fieser rule. 1. Presented by: cy 1st yr Department of pharmaceutical analysis; 2. Introduction. WOODWARD-. 5 May Brief description of Woodward Fieser Rules. * Examples for all te 3 rules. Using Woodward-Fieser’s rule, calculate wavelengths of maximum UV absorption for following compounds: a) b) c). Base value: nm. Base value: nm.
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feser If we start with the alkene at the bottom left, then it is in conjugation with an endocyclic alkene to the immediate right and an exocyclic alkene in the ring to the right hand side.
Inputs used in the calculation are the type of chromophores present, the substituents on the chromophores, and shifts due to the solvent.
One set of Woodward—Fieser rules for dienes is outlined in table 1. Rulr you try this for your molecule you’ll quickly see that the bond you’ve highlighted is too distant from the conjugated system to have any involvement.
Exocyclic is defined as being fueser of the ring system or in more complex systems, outside of the ring system being consideredthe bond highlighted is indeed inside the ring system and is as such endocyclic. But according to the paper by Fieser the pointed double bond is exocyclic to the 5 membered ring or right.
Archived from the original on April 10, Woodward Fieser rules for dienes – non conjugated double bond as exocyclic? From Wikipedia, the free encyclopedia.
Views Read Edit View history. When looking for exocyclic double bonds in a diene, should a double bond not connected to the conjugated system rlue considered? Fieser; Mary Fieser; Srinivasa Rajagopalan Should the marked double bond considered wkodward an exocyclic double bond? Retrieved from ” https: In the compound on the right, the diene is homoannular with 4 alkyl substituents. Both double bonds in the central B ring are exocyclic with respect to rings A and C.
These double bonds are all in conjugation with one another.
What I want to know is whether a double bond must be a part of the conjugated system for it to be considered as an exocyclic double bond in the calculation? Central Connecticut State University. So, the pointed double bond is exocyclic to the adjoining cyclopentane ring.
Thanks for the answer. For polyenes having more than 4 conjugated double bonds one must use Fieser—Kuhn rules. Alkyl substituent or ring residue. For example, in this compound, should the marked double bond considered as an exocyclic double bond?
Physical organic chemistry Spectroscopy.
Sign up or log in Sign up using Google. Woodward’s rules are an empirical method for predicting the maximum absorption of a molecule based on the functional groups present that is, conjugated functional groups which possess a distinctive maximum absorbance such as a diene or an unsaturated carbonyl.
If you find a double bond outside a ring as in the 4 ring system hereit will be considered as exocyclic.