双语化学辞典Chem Lexicon
本科Undergraduate 分子光谱与结构测定 Molecular spectroscopy & structure determination

伍德沃德–菲泽规则Woodward–Fieser rules

\[\lambda_\text{max} = \lambda_\text{母体} + \sum \Delta\lambda_i\]\[\lambda_\text{max} = \lambda_\text{parent} + \sum \Delta\lambda_i\]
共轭二烯的增量（乙醇中）increments for conjugated dienes (ethanol)
\[\text{共轭二烯：母体 } 214\ (\text{同环 }253)\ \mathrm{nm};\ \text{每个烷基/环残基 }+5;\ \text{环外双键 }+5;\ \text{延长共轭双键 }+30\]\[\text{conj. diene : parent} 214\ (\text{homoannular}253)\ \mathrm{nm};\ \text{each alkyl / ring residue}+5;\ \text{exocyclic C=C}+5;\ \text{extending C=C}+30\]
α,β-不饱和羰基化合物α,β-unsaturated ketones
\[\alpha,\beta\text{-不饱和酮：母体 } 215\ \mathrm{nm};\ \alpha\text{-烷基 }+10;\ \beta\text{-烷基 }+12;\ \gamma, \delta\ +18\]\[\alpha,\beta\text{- unsat. ketone : parent} 215\ \mathrm{nm};\ \alpha\text{- alkyl}+10;\ \beta\text{- alkyl}+12;\ \gamma, \delta\ +18\]

含义Meaning

按母体加增量的经验规则估算共轭体系 π→π* 吸收的最大波长，曾在天然产物（萜类、甾体）结构鉴定中广泛使用。

Empirical parent-plus-increments rules estimating λ_max of π→π* bands in conjugated systems, once central to identifying terpenes and steroids.

符号说明Symbols

符号Symbol含义 Meaning单位 Unit
\(\lambda_\text{max}\)最大吸收波长wavelength of maximum absorptionnm
\(\Delta\lambda_i\)取代基、环、共轭的增量increments for substituents, rings, conjugationnm

推导Derivation

  1. 伍德沃德（1941–1942）对大量甾体和萜类的实测光谱归纳出各结构因素的贡献，菲泽夫妇后来加以修订扩充。

    Woodward (1941–42) extracted increments from many steroid and terpene spectra; the Fiesers later refined them.

  2. 物理上，共轭延长、给电子取代基使 HOMO–LUMO 能隙减小，吸收红移（与箱中粒子模型一致）。

    Physically, extended conjugation and donor substituents narrow the HOMO–LUMO gap, red-shifting absorption.

适用条件与局限Assumptions & limitations

  • 只适用于不超过约四个共轭双键的体系；更长的多烯用费泽–库恩规则。

    Up to about four conjugated double bonds; longer polyenes use Fieser–Kuhn.

  • 扭曲、空间位阻导致共轭不共平面时预测失效；溶剂校正需另加。

    Fails when sterics twist the chromophore; solvent corrections are separate.

例题Worked example

2,3-二甲基-1,3-丁二烯：214 + 2×5 = 224 nm（实测 226 nm）。

2,3-Dimethyl-1,3-butadiene: 214 + 10 = 224 nm (observed 226).