含义Meaning
按化学计量式，目标产物质量占全部反应物质量的比例。绿色化学的核心指标之一（Trost，1991）。
From the balanced equation, the fraction of reactant mass that ends up in the desired product — a core green-chemistry metric (Trost, 1991).
符号说明Symbols
| 符号Symbol | 含义 Meaning | 单位 Unit |
|---|---|---|
| \(\nu_i\) | 化学计量数stoichiometric coefficient | 1 |
| \(M\) | 摩尔质量molar mass | g·mol⁻¹ |
| \(E\) | E 因子：每千克产物产生的废物千克数E-factor: kg waste per kg product | 1 |
推导Derivation
写出配平方程式，所有反应物的总质量 \(\sum\nu_iM_i\) 等于全部产物总质量（质量守恒）。
From the balanced equation, total reactant mass \(\sum\nu_iM_i\) equals total product mass.
其中只有目标产物的部分是“有用”的，取其比值。
Only the desired product’s share is useful; take the ratio.
加成、重排反应 AE = 100%；取代、消除反应必然产生副产物，AE < 100%。
Additions and rearrangements have AE = 100 %; substitutions and eliminations always produce by-products.
适用条件与局限Assumptions & limitations
只看计量式，不考虑产率、溶剂、催化剂、后处理产生的废物；实际评价应结合产率和 E 因子。
Ignores yield, solvents, catalysts and work-up waste; combine with yield and E-factor.
不反映毒性和能耗。
Says nothing about toxicity or energy use.
例题Worked example
乙烯与水加成制乙醇 AE = 100%；溴乙烷与 NaOH 取代：AE = 46/(109+40) = 31%。
Ethene + water → ethanol: AE = 100 %. Bromoethane + NaOH → ethanol: AE = 46/(109 + 40) = 31 %.