查看“︁塔夫特方程”︁的源代码

{| class="wikitable" style="float:right;"
|-
|+塔夫特方程中的参数值<ref>Eric Anslyn, E.; Dougherty, D. A. ''Modern Physical Organic Chemistry''; University Science Books, 2006, p 455.</ref>
|-
!| 取代基 || E<sub>s</sub> || σ*
|-
|| –H || 1.24 || 0.49
|-
|| –CH<sub>3</sub> || 0 || 0
|-
|| –CH<sub>2</sub>CH<sub>3</sub> || –0.07 || –0.1
|-
|| –CH(CH<sub>3</sub>)<sub>2</sub> || –0.47 || –0.19
|-
|| –C(CH<sub>3</sub>)<sub>3</sub> || –1.54 || –0.3
|-
|| –CH<sub>2</sub>Ph || –0.38 || 0.22
|-
|| –Ph || –2.55 || 0.6
|}

'''塔夫特方程'''（{{lang-en|'''Taft equation'''}}）是[[物理有机化学]]中的一种[[线性自由能关系]]方程，用于研究[[反应机理]]和有机化合物的[[定量结构-活性关系]]。1952年由[[罗伯特·W·塔夫特]]提出，作为对[[哈米特方程]]的一种改进。<ref>{{Cite journal|last=Taft|first=Robert W.|date=June 1952|title=Linear Free Energy Relationships from Rates of Esterification and Hydrolysis of Aliphatic and Ortho-substituted Benzoate Esters|url=https://pubs.acs.org/doi/abs/10.1021/ja01131a010|journal=Journal of the American Chemical Society|language=en|volume=74|issue=11|pages=2729–2732|doi=10.1021/ja01131a010|issn=0002-7863|access-date=2024-07-16|archive-date=2024-07-16|archive-url=https://web.archive.org/web/20240716081048/https://pubs.acs.org/doi/abs/10.1021/ja01131a010|dead-url=no}}</ref><ref>{{Cite journal|last=Taft|first=Robert W.|date=1952-06-01|title=Polar and Steric Substituent Constants for Aliphatic and o-Benzoate Groups from Rates of Esterification and Hydrolysis of Esters1|url=https://doi.org/10.1021/ja01132a049|journal=Journal of the American Chemical Society|volume=74|issue=12|pages=3120–3128|doi=10.1021/ja01132a049|issn=0002-7863}}</ref><ref>{{Cite journal|last=Taft|first=Robert W.|date=1953-09-01|title=Linear Steric Energy Relationships|url=https://doi.org/10.1021/ja01114a044|journal=Journal of the American Chemical Society|volume=75|issue=18|pages=4538–4539|doi=10.1021/ja01114a044|issn=0002-7863}}</ref>
哈米特方程考虑了[[场效应]]、[[诱导效应]]和[[共振]]的影响<ref>{{Cite journal|last=Hammett|first=Louis P.|date=1937-01-01|title=The Effect of Structure upon the Reactions of Organic Compounds. Benzene Derivatives|url=https://doi.org/10.1021/ja01280a022|journal=Journal of the American Chemical Society|volume=59|issue=1|pages=96–103|doi=10.1021/ja01280a022|issn=0002-7863}}</ref>
，塔夫特方程则进一步考虑了[[位阻效应]]的影响。

塔夫特方程的形式为：

:<math chem>\log\left ( \frac{k_s}{k_{\ce{CH3}}} \right )= \rho^*\sigma^* + \delta E_s</math>

式中<math chem>\log\frac{k_s}{k_\ce{CH3}}</math>是带有某取代基的有机物的取代反应与参考反应（取代基为甲基时）的反应速率常数比；<math chem>\rho^*</math>是该反应对极性效应的敏感因子；<math chem>\sigma^*</math>是极性取代常数，可以描述[[取代基]]的场效应和诱导效应；<math chem>\delta</math>是该反应对位阻效应的敏感因子，而<math chem>E_s</math>是位阻取代基常数。

==参考文献==
<references/>

[[category:物理有机化学]]
[[category:方程]]