Show how each of the following compounds can be synthesized...

Key Concepts

Epoxidation and Ring-Opening Reactions

Alkenes can be converted to epoxides via reaction with peroxy acids, a process that proceeds with syn addition. The resultant epoxides are versatile intermediates because they can undergo nucleophilic ring-opening reactions under acidic or basic conditions, forming various functionalized products. This sequence offers a valuable synthetic route to build complex molecular architectures from simple alkene precursors.

Halogenation and Halohydrin Formation

Alkenes can react with halogens, such as Br2 or Cl2, to form vicinal dihalides through an electrophilic addition mechanism. When the halogenation is carried out in the presence of water, halohydrin formation occurs. In this reaction, the nucleophilic solvent (water) attacks the intermediate halonium ion, resulting in the formation of a product containing both a halogen and a hydroxyl group.

Anti-Markovnikov Conditions and Hydroboration-Oxidation

Under specific conditions, alkenes can undergo additions that proceed with anti-Markovnikov selectivity. A classic example is the hydroboration-oxidation sequence, where borane adds across the double bond to give an organoborane intermediate that is oxidized to form an alcohol on the less substituted carbon, providing a complementary method for regioselective synthesis.

Markovnikov's Rule

In many electrophilic additions to alkenes, the regioselectivity is determined by Markovnikov's rule. This principle states that the electrophile adds to the less substituted carbon of the double bond, leading to the formation of the more stable, more substituted carbocation intermediate. This rule is key when synthesizing compounds like alcohols or halides from alkenes.

Electrophilic Addition Reactions

Alkenes are electron?rich species that react with electrophiles to initiate addition reactions. These reactions typically proceed via formation of a high?energy carbocation intermediate that is subsequently attacked by a nucleophile, enabling the incorporation of new functional groups across the double bond.

Transcript

00:03 Let's try synthesizing the following compounds from alkenes.

00:08 Well, if we take this first one and we know we're adding this part because that's an easy substituent to add.

00:20 So if we look at that, well, we can say that our alken was this molecule, propene.

00:29 And what we added was this substituent, which would be methanol.

00:40 Under catalytic h2s -o -4.

00:45 And we can do that to produce this ether.

00:54 For the next one, well, we're adding two bromines.

00:58 So right off the bat, we can just remove them and say that the carbons between them have a double bond, and we're adding br2.

01:14 For this one, well, we can say that we're adding this alcohol group.

01:20 So if we remove that and put a double bond, with the carbons involved.

01:26 There's only one carbon bonded close to that alcohol, so we will have to use this alken.

01:33 And if we want to produce this alcohol, we're going to have to use anti -marcovnikov addition, because we want it on this carbon, which would mean we add borohyd, thf, and we use h202, h2o, and so, some type of base.

02:02 For this one, we can remove our added group, which is usually going to be the fancy group.

02:09 We're looking at alcohols, ethers, halogens, anything with an oxygen or a halogen is kind of a safe bet with these problems.

02:22 If you're trying to synthesize molecules using alkenes, what you're looking for is something that'll add oxygen.

02:31 Something that'll add halogens.

02:34 So if we just remove that entirely, what we end up getting is we can have one of two alkenes.

02:41 We can have this alkenes or we can have this alken.

02:47 Now, i'm going to use this alken because it's a more stable and more commercially available alken than this one...

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