《ART》章末总结1

最近开始看《The Art of Writing Reasonable Organic Reaction Mechanisms》，简称《ART》。当初学竞赛的时候就一直想着看，但是没看多少还是弃了，现在打算补上来，算是了结心愿。每章看完写个post复盘一下。

1.7 Summary

Getting started is usually the most difficult part of drawing a mechanism.Follow these simple steps, and you will be well on your way.

Label the heavy atoms in starting material and product. 把反应物和产物的对应重原子（除H之外的原子）标号。
Make a list of which σ bonds between non-H atoms are made or broken in going from starting material to product. Do not list π bonds or bonds to H, as they are easier to make and break at will. 将反应物转化为产物过程中非H原子间σ键的断裂和形成列表记录。不用记录π键和C-H键，因为它们很容易随意形成/断裂。
Balance the reaction. 配平反应。
Classify the overall reaction by looking at the starting materials and products, including by-products. Is the reaction an additon, an elimination, a substitution, or a rearrangement? Some reactions may combine two or more of these types. 通过观察反应物，产物和副产物给反应从整体上分类。该反应是加成，消去，取代还是重排？有一些反应可能包括两种及以上的反应类型。
Classify the mechanism by looking at the reaction conditions. Is it polar under basic conditions, polar under acidic conditions, free-radical, pericyclic, or metal-mediated? Some reactions, especially pericyclic ones, may combine two or more of these types. 通过观察反应条件判断机理类型。该反应是在碱性/酸性条件的极性机理，自由基机理，周环机理还是金属有机？一些反应（尤其是周环反应）可能涉及两种及以上机理类型。
(Once you have classified the overall reaction and the mechanism, you may have a short series of mechanistic choices. For example, substitution of an aromatic ring under basic conditions generally occurs by one of three mechanisms. 一旦你已经确定反应类型和机理，你就有了一系列的机理选择。例如，碱性条件下的芳环上的(亲核)取代通常是三选一(加成消除、苯炔中间体、SRN1)。)
If the mechanism is polar, determine the nucleophilicity, electrophilicity, and acidity of the atoms to which σ bonds are made and broken. Under basic conditions, the first step is often deprotionation of an acidic atom, rendering it nucleophilic. Under acidic conditions, the first step may be protonation of a leaving group or a π bond. 如果是极性机理，确定（试剂）的亲核性、亲电性，以及成/断键的原子的酸性。碱性条件下，第一步通常是酸性原子的去质子化，使其亲核性增加。酸性条件下，第一步通常是离去基团或π键质子化。

When faced with a mechanism problem, students often ask, How does one know that a particular nucleophile attacks a particular electrophile to give a particular product? 面对一个机理问题时，学生们常问，我怎么知道哪个亲核试剂进攻哪个亲电试剂然后生成什么产物？

The answer to this question is relatively straightforward. A mechanism is a story that you tell about how compound A is transformed into compound B. 问题的答案其实相当朴实无华。一个机理就是你讲一个化合物A如何变成化合物B的故事。

To tell the story, you need to know what the product is! If you do not know what the product is, your story will sound something like the game in which 15 children in turn add one paragraph to a continuing story, and the final version wanders all over the known universe. 要讲这个故事，你得知道产物是什么！如果你不知道的话，你的故事就会听起来像是15个小孩的故事接龙，结果离谱到像是在漫游宇宙。

Sometimes the product will be a minor or unexpected product, but a mechanism problem will always give you the product. 有些时候产物是次要产物或者在预期之外，但是机理题总是会给你产物。

Organic chemists do need to learn how to predict the product of a reaction, but this skill is deemphasized in this text, whose purpose is to help you to learn how to write mechanisms. Only occasionally will you be asked to predict the course of a reaction. 有机化学家们确实需要学习如何预测反应产物，但是这个技巧在该书被淡化，因为本书目的是为了帮助你学习写机理。只是偶尔可能会让你预测反应过程。

第一章都是一些基础概念，和邢大本上东西异曲同工。不过国外教材有一点好处是解释很详细，不厌其烦地举例和阐释，便于加深理解。

写机理的步骤也是十分详细，但是一些简单反应其实用不到一步一步来。比如说标号，如果遇到碳骨架变化很大或者结构复杂的题，一眼看不明白的话，就可以按照他的思路标号对照了。

再就是质子化的问题，国内教材很多机理都不很标准，经常漏步，有时也不写质子化，我当时练机理还是做的福山题，足够详细严谨。

课后习题有空的话挑几道写写。