|
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. Inputs used in the calculation are the type of chromophores present, the substituents on the chromophores, and shifts due to the solvent. Examples are conjugated carbonyl compounds, conjugated dienes,〔 and polyenes.〔〔 ==Implementation== 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. With the aid of these rules the UV absorption maximum can be predicted, for example in these two compounds:〔''Organic spectroscopy'' William Kemp〕 In the compound on the left, the base value is 214 nm (a heteroannular diene). This diene group has 4 alkyl substituents (labeled 1,2,3,4) and the double bond in one ring is exocyclic to the other (adding 5 nm for an exocyclic double bond). 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. For polyenes having more than 4 conjugated double bonds one must use Fieser-Kuhn rules.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Woodward's rules」の詳細全文を読む スポンサード リンク
|