Chapter 13: Problem 7
Propanal and pentan-3-one are the ozonolysis products of an alkene? What is the structural formula of the alkene?
Short Answer
Expert verified
The alkene is oct-4-ene (\( CH_3CH_2CH=CHCH_2CH_2CH_3 \)).
Step by step solution
01
Understanding the Ozonolysis Reaction
Ozonolysis is a reaction where ozone (O₃) reacts with an alkene to break the carbon-carbon double bond, resulting in the formation of two carbonyl compounds, typically aldehydes or ketones.
02
Identify the Products
The products given are propanal and pentan-3-one. Propanal is an aldehyde with the formula \( C_3H_6O \) and pentan-3-one is a ketone with the formula \( C_5H_{10}O \).
03
Determine the Structure of Propanal and Pentan-3-one
Propanal has the structure \( CH_3CH_2CHO \), and pentan-3-one has the structure \( CH_3CH_2COCH_2CH_3 \).
04
Establish the Carbon Chain
Since propanal and pentan-3-one come from the same alkene, the carbons from both compounds will add up to the total number of carbons in the initial alkene. Propanal has 3 carbons and pentan-3-one has 5 carbons, totaling 8 carbons.
05
Determine the Original Alkene Structure
The original alkene must have a carbon chain that, when cut by ozonolysis, splits into the carbon chains of propanal and pentan-3-one. The total carbon count should be 8. This suggests the alkene is oct-4-ene, which can be split to form these ozonolysis products.
06
Draw the Structure of Oct-4-ene
The structure of oct-4-ene is \( CH_3CH_2CH=CHCH_2CH_2CH_3 \). When ozonolysis occurs, the double bond at the center breaks to form the given ozonolysis products.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Alkenes
Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (\(C=C\)). This double bond is key because it makes alkenes more reactive than alkanes, which only contain single bonds. In the structure of alkenes, double bonds introduce the possibility of geometric isomerism. For example, ethene (or ethylene), the simplest alkene, is a colorless gas with the formula \(C_2H_4\).
Let's delve deeper into the structure. Alkenes can have linear, branched, or even cyclic structures, but the defining feature remains the double bond. This bond is made of one sigma bond and one pi bond, where the pi bond is responsible for the high reactivity of alkenes during addition reactions, such as ozonolysis.
During ozonolysis, the double bond is cleaved, leading to two separate carbon fragments that originally held the double bond. In our example, ozonolysis transforms the alkene oct-4-ene into the carbonyl compounds propanal and pentan-3-one. This ability to break apart into smaller molecules makes alkenes extremely valuable in synthetic organic chemistry.
Let's delve deeper into the structure. Alkenes can have linear, branched, or even cyclic structures, but the defining feature remains the double bond. This bond is made of one sigma bond and one pi bond, where the pi bond is responsible for the high reactivity of alkenes during addition reactions, such as ozonolysis.
During ozonolysis, the double bond is cleaved, leading to two separate carbon fragments that originally held the double bond. In our example, ozonolysis transforms the alkene oct-4-ene into the carbonyl compounds propanal and pentan-3-one. This ability to break apart into smaller molecules makes alkenes extremely valuable in synthetic organic chemistry.
Carbonyl Compounds
Carbonyl compounds are a broad group of organic molecules that incorporate a carbonyl group \(C=O\) in their structure. The carbonyl group consists of a carbon atom double-bonded to an oxygen atom, and it's a central feature of many organic compounds, including aldehydes, ketones, carboxylic acids, and esters.
In the original exercise, the carbonyl compounds described are propanal (an aldehyde) and pentan-3-one (a ketone). Aldehydes have the general formula \(RCHO\), where \(R\) is a hydrogen or any hydrocarbon group. Propanal fits this structure with \(CH_3CH_2CHO\).
Ketones, on the other hand, have the general formula \(RCOR'\), where \(R\) and \(R'\) are hydrocarbon groups. Pentan-3-one is a ketone with the structure \(CH_3CH_2COCH_2CH_3\). These carbonyl compounds, especially ketones and aldehydes, are significant in many fields due to their reactivity and use in forming more complex molecules.
In the original exercise, the carbonyl compounds described are propanal (an aldehyde) and pentan-3-one (a ketone). Aldehydes have the general formula \(RCHO\), where \(R\) is a hydrogen or any hydrocarbon group. Propanal fits this structure with \(CH_3CH_2CHO\).
Ketones, on the other hand, have the general formula \(RCOR'\), where \(R\) and \(R'\) are hydrocarbon groups. Pentan-3-one is a ketone with the structure \(CH_3CH_2COCH_2CH_3\). These carbonyl compounds, especially ketones and aldehydes, are significant in many fields due to their reactivity and use in forming more complex molecules.
Reaction Mechanism
The term 'reaction mechanism' refers to the detailed step-by-step process by which reactants are transformed into products in a chemical reaction. Understanding mechanisms is crucial as it allows chemists to predict the products of reactions and design new synthetic pathways.
In ozonolysis of alkenes, the reaction mechanism involves several steps. Initially, ozone adds to the carbon-carbon double bond to form an unstable intermediate called a molozonide. This rapidly rearranges into a more stable ozonide structure. Under reductive workup conditions, such as in the presence of zinc and water, this ozonide breaks down into carbonyl compounds.
In our example involving oct-4-ene, the double bond breaks and forms propanal and pentan-3-one upon ozonolysis. This reveals the power of reaction mechanisms in understanding how all components fit together during chemical transformations.
In ozonolysis of alkenes, the reaction mechanism involves several steps. Initially, ozone adds to the carbon-carbon double bond to form an unstable intermediate called a molozonide. This rapidly rearranges into a more stable ozonide structure. Under reductive workup conditions, such as in the presence of zinc and water, this ozonide breaks down into carbonyl compounds.
In our example involving oct-4-ene, the double bond breaks and forms propanal and pentan-3-one upon ozonolysis. This reveals the power of reaction mechanisms in understanding how all components fit together during chemical transformations.
