Most people know the names of the common classes of biomolecules—proteins, carbohydrates, lipids, and nucleic acids—but there are many more kinds of compounds in living organisms than just those four. All living organisms also contain a vast diversity of substances…
How do we know that the carbocation mechanism for electrophilic addition reactions of alkenes is correct? The answer is that we don’t know it’s correct; at least we don’t know with complete certainty. Although an incorrect reaction mechanism can be disproved by…
Let’s summarize what we’ve learned of electrophilic addition reactions to this point: What we have not yet seen is how these two points are related. Why does the stability of the carbocation intermediate affect the rate at which it’s formed…
To understand why Markovnikov’s rule works, we need to learn more about the structure and stability of carbocations and about the general nature of reactions and transition states. The first point to explore involves structure. A great deal of experimental…
Look carefully at the electrophilic addition reactions shown in the previous section. In each case, an unsymmetrically substituted alkene has given a single addition product rather than the mixture that might be expected. For example, 2-methylpropene might react with HCl…
Before beginning a detailed discussion of alkene reactions, let’s review briefly some conclusions from the previous chapter. We said in Section 6.5 that alkenes behave as nucleophiles (Lewis bases) in polar reactions, donating a pair of electrons from their electron-rich C═CC═C bond to an…
happen by treating the alkene with a strong acid catalyst. If we interconvert cis-2-butene with trans-2-butene and allow them to reach equilibrium, we find that they aren’t of equal stability. The trans isomer is more stable than the cis isomer by 2.8…
The cis–trans naming system used in the previous section works only with disubstituted alkenes—compounds that have two substituents other than hydrogen on the double bond. With trisubstituted and tetrasubstituted double bonds, a more general method is needed for describing double-bond…
We saw in the chapter on Structure and Bonding that the carbon–carbon double bond can be described in two ways. In valence bond language (Section 1.8), the carbons are sp2-hybridized and have three equivalent hybrid orbitals that lie in a plane at angles…
Alkenes are named using a series of rules similar to those for alkanes (Section 3.4), with the suffix -ene used instead of -ane to identify the functional group. There are three steps to this process. STEP 1Name the parent hydrocarbon. Find the longest carbon chain…