In this next series of posts we are going to discuss the reactions of alcohols. As a functional group, alcohols are introduced fairly early in organic chemistry. Their reactions, however, are usually not covered until near the end of Org 1 - at least after subjects like substitution and … [Read more...]
Bond Strengths And Radical Stability
EDIT: More caution is required than I had previously indicated regarding the main thesis of this post - that free radical stabilities are solely reflected by bond strengths. They depend on the stability of both reactant and reagent. Edits are indicated inline. For more discussion see bottom … [Read more...]
3 Factors That Stabilize Free Radicals
In the last post we introduced free radicals - neutral, electron-deficient chemical species with a partially filled orbital - and learned that they are highly reactive intermediates in organic chemistry. In this post we'll cover two of the most important concepts concerning these species: their … [Read more...]
The E1 Reaction
Last time in this walkthrough on elimination reactions, we talked about two types of elimination reactions. In this post, we're going to dig a little bit deeper on one type of elimination reaction, and based on what experiments tell us, come up with a hypothesis for how it works. Here's the … [Read more...]
Two Types of Substitution Reactions
Chemistry is an experimental science. There is no great Ramanujan of our discipline, who, starting with a simple set of premises, could derive and predict all of the depth and variety of modern chemistry. No, it is much messier than that. Chemists have to actively interrogate Nature to learn her … [Read more...]
3 Factors That Stabilize Carbocations
Three main factors increase the stability of carbocations: Increasing the number of adjacent carbon atoms: methyl (least stable carbocation) < primary < secondary < tertiary (most stable carbocation) Adjacent pi bonds that allow the carbocation p-orbital to be part of a conjugated … [Read more...]
Bond Dissociation Energies = Homolytic Cleavage
Here's a point which causes a lot of confusion. Look at these two reactions. What do you think is the stronger bond, O-H or C-H? According to this this table (PDF) the bond dissociation energy (BDE) of OH is 460 kJ/mol (110 kcal/mol) and the value for CH is 389 kJ/mol (93 kcal/mol). [For … [Read more...]
Primary, Secondary, Tertiary, Quaternary In Organic Chemistry
Organic chemists, with carbon chemistry as their subject, have developed all kinds of shorthand phrases to describe structures and phenomena that might otherwise take a sentence of two to explain. Here's today's example: the terminology of carbon-containing functional groups: primary, secondary, … [Read more...]