In the following posts, we will learn about and do many practice problems on Nucleophilic Substitution Reactions. Nucleophilic Substitution Reactions are one of the most important major classes of organic chemistry and essential that you build a solid foundation and understanding of their principles and mechanisms such as the SN1 and SN2 reactions.
We will start from the introduction and general features of Nucleophilic Substitution Reactions and go in detail individually for the SN1 and SN2 mechanism. Each practice problem is designed to address the specifics of these mechanisms; the reactivity, stereochemistry and possibility of rearrangements. For example, you will have many practice problem examples that demonstrate in detail the inversion of R and S configuration during SN2 reactions. On the other hand, we will also see why a racemic mixture is obtained when the reaction goes by the SN1 mechanism via the formation of a carbocation intermediate.
One important and yet overwhelming questions in Nucleophilic Substitution Reactions is the prediction of the mechanism as to whether it is SN1 or SN2. And we will talk about how to choose between SN1 and SN2 considering the nucleophile, the substrate, the solvent, and the reaction conditions. Once you have sufficient knowledge, we will so do the retrosynthetic analysis of Nucleophilic Substitution Reactions to learn the best of choosing a reagent for functional group transformations.
Alkyl halides can be converted to alcohols by reacting them with water or hydroxide ion. Recall that the hydroxide ion is a good nucleophile, and water is a poor nucleophile; therefore, the conversions occur via SN2 and SN1 mechanisms, respectively. … Read more
Ring Strain and Ring Expansion The title of today’s discussion contains two keywords: Ring Expansion and Rearrangement. So, what are those? A ring expansion is the transformation of a smaller ring to a larger ring. A rearrangement is a change … Read more
The SN1 mechanism is a unimolecular process, which means only the substrate participates in the rate-determining step of the reaction. The rate-determining step is the loss of the leaving group, which forms a carbocation. There are a few main features … Read more
Alkyl halides react with water by SN1 mechanism forming alcohols. Let’s put together some examples of these hydrolysis reactions of alkyl halides and address some important concepts such as the mechanisms, stereochemistry, the relationship of products, and different types of … Read more
Before talking about common exceptions in SN2 and SN1 reactions, let’s recall the main patterns we learned about them: 1) SN2 is favored for primary alkyl halides 2) SN1 is favored for tertiary alkyl halides 3) SN2 proceeds via inversion … Read more
This article is written to address the topic that starts causing lots of confusion when the explanation deviates from the “in SN2, a wedge becomes a dash, and a dash becomes a wedge” statement. So, let’s start with this statement … Read more
Earlier on, when discussing the reactions of alcohols, we learned that the hydroxyl group is not a (good) leaving group, and one of the ways to address this problem was converting it into a mesylate or tosylate group. These are … Read more
In simple words, the Hammond postulate predicts whether the transition state resembles the reactant or the product of the reaction. According to it, the transition state resembles the structure of the species (reactant, intermediate, or product), which is closer to … Read more
We have seen many times when discussing the SN2 mechanism that ethers are common products of nucleophilic substitution reactions. They are synthesized by reacting alkyl halides or other substrates with good leaving groups with alkoxides: This method of … Read more
Alcohols can be converted to alkyl halides by reacting with HX (X = Cl, Br, I) acids. The reaction works for 1°, 2°, and 3° alcohols: Let’s now understand how this happens. We have seen many times in … Read more
