A. The following product was obtained from the ozonolysis of...

a. The following product was obtained from the ozonolysis of an alkene followed by treatment with dimethyl sulfide. What is the structure of the alkene? b. The following products were obtained from the oxidative cleavage of a diene. What is the structure of the diene? SOLUTION TO 33 a. Because only one product is obtained, the reactant must be a cyclic alkene. Numbering the product shows that the carbonyl groups are at $\mathrm{C}-1$ and $\mathrm{C}-6,$ so the double bond in the alkene must be between $\mathrm{C}-1$ and $\mathrm{C}-6,$. SOLUTION TO 33 b. The five-carbon product with two carbonyl groups indicates that the diene must contain five carbons flanked by two double bonds. One of the other two products obtained from ozonolysis has one carbon, and the other has three carbons. Therefore, one carbon must be added to one end of the diene, and three carbons must be added to the other end.

a. The following product was obtained from the ozonolysis of an alkene followed by treatment with dimethyl sulfide. What is the structure of the alkene?
b. The following products were obtained from the oxidative cleavage of a diene. What is the structure of the diene?
SOLUTION TO 33 a. Because only one product is obtained, the reactant must be a cyclic alkene. Numbering the product shows that the carbonyl groups are at $\mathrm{C}-1$ and $\mathrm{C}-6,$ so the double bond in the alkene must be between $\mathrm{C}-1$ and $\mathrm{C}-6,$.
SOLUTION TO 33 b. The five-carbon product with two carbonyl groups indicates that the diene must contain five carbons flanked by two double bonds.
One of the other two products obtained from ozonolysis has one carbon, and the other has three carbons. Therefore, one carbon must be added to one end of the diene, and three carbons must be added to the other end.

Key Concepts

Cyclic Alkene Considerations

Cyclic alkenes, due to their ring structure, often lead to unique outcomes in ozonolysis. The symmetry of a cyclic system typically results in a single set of cleavage products, which simplifies the analysis and helps confirm the position of the double bond within the ring.

Ozonolysis

Ozonolysis is a cleavage reaction where ozone reacts with carbon-carbon multiple bonds to break them, forming reactive intermediates (ozonides) that can be transformed into carbonyl compounds. It is a valuable tool for determining the locations of double bonds in alkenes, and the nature of the reaction products provides insight into the original molecular structure.

Dimethyl Sulfide Workup

A dimethyl sulfide workup is used following ozonolysis to reduce the intermediate ozonide to stable carbonyl compounds. This step prevents overoxidation and helps ensure that the derived products accurately reflect the original arrangement of the carbon skeleton in the starting alkene.

Oxidative Cleavage

Oxidative cleavage refers to the breaking of carbon–carbon double bonds using an oxidizing agent, resulting in the formation of smaller fragments, usually carbonyl compounds. This reaction provides essential structural information, especially when multiple products are formed, as it can reveal the arrangement and number of carbon atoms between reactive sites.

Structure Determination from Reaction Products

Structure determination from reaction products involves deducing the original molecular structure by analyzing the fragments obtained from a chemical reaction. By considering the number and type of carbonyl products, one can infer the positions of double bonds and the overall framework of the precursor molecule, offering a reverse-engineering approach to organic synthesis.

Transcript

00:01 All right, so in this question we're given ozenolysis products and asked to determine what is the likely reactant.

00:07 So the first thing we have is this guy right here, like that.

00:19 And we're going to draw retro synthetic errors, kind of this double -ended error, to show that we're working backwards.

00:25 So obviously we've got two carboneals, meaning there was probably two kind of available sites for cleavage.

00:32 But we know we only have one product.

00:34 So this probably was some sort of a range structure.

00:37 Now since the carboneals are more than likely the site of cleavage, we can say this is one, two, three, four, five, six, right? so that obviously kind of shows that we have some sort of six -membered ring like this, right? where we just have an alkyne right here.

00:56 Notice though at carbon one, we have a methyl substituent, meaning we probably have a methyl kind of just off the edge like that.

01:03 All right, b is just a little more complicated where we've got several, products.

01:10 The first being a one, two, three, four, five member thing.

01:14 So we have something that looks like this.

01:26 No, we also have two other products.

01:31 The first just being something looks like this.

01:35 And the third being something that looks like this.

01:42 Okay.

01:43 So we can probably expect that this is going to be a very, very, very, long carbon chain with multiple double bonds.

01:54 So one way to do this is first just count up all the carbons and label all of the chains...

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