Question

Write IUPAC names of the products obtained by the ozonolysis of the following compounds : (i) \(\quad\) Pent-2-ene (ii) 3,4 -Dimethylhept-3-ene (iii) \(\quad\) 2-Ethylbut-1-ene (iv) \(\quad\) 1-Phenylbut- 1 -ene

Short answer

1. Ethanal and Propanal; 2. Propan-2-one and 4-Methylpentanal; 3. Ethanal and Propanal; 4. Benzaldehyde and Propanal.

Step-by-step solution

Understand Ozonolysis Reaction

Ozonolysis is a reaction where the double bonds of alkenes are cleaved by ozone, followed by workup with water or other reducing agents, to form carbonyl compounds. Essentially, each double bond ( C=C ) is broken and replaced with two carbonyl groups (C=O).

Identify Double Bonds in the Compounds

For each compound, identify the position of the carbon-carbon double bond. This is crucial as ozonolysis specifically targets these bonds. Note: 1. Pent-2-ene: Double bond is between C2 and C3. 2. 3,4-Dimethylhept-3-ene: Double bond is between C3 and C4. 3. 2-Ethylbut-1-ene: Double bond is between C1 and C2. 4. 1-Phenylbut-1-ene: Double bond is between C1 and C2.

Perform Ozonolysis

Now, use ozonolysis on each compound: 1. **Pent-2-ene** splits into two molecules: Ethanal (CH₃CHO) and Propanal (C₂H₅CHO). 2. **3,4-Dimethylhept-3-ene** splits into: Acetone ((CH₃)₂CO) and 4-Methylpentanal (C₄H₉CHO). 3. **2-Ethylbut-1-ene** splits into: Acetaldehyde (CH₃CHO) and Propanal (C₂H₅CHO). 4. **1-Phenylbut-1-ene** splits into: Benzaldehyde (C₆H₅CHO) and Propanal (C₂H₅CHO).

Write IUPAC Names of the Products

Convert the names obtained from ozonolysis into standard IUPAC nomenclature: 1. Pent-2-ene yields Ethanal and Propanal. 2. 3,4-Dimethylhept-3-ene yields Propan-2-one and 4-Methylpentanal. 3. 2-Ethylbut-1-ene yields Ethanal and Propanal. 4. 1-Phenylbut-1-ene yields Benzaldehyde and Propanal.

Key concepts

Ozonolysis

Ozonolysis is an important reaction in organic chemistry, utilized primarily for breaking down alkenes. In this process, ozone ( O₃ ) reacts with the carbon-carbon double bonds ( C=C ) in alkenes, cleaving them completely. After the initial reaction with ozone, the compound is treated with a reducing agent, which typically involves water or dimethyl sulfide, resulting in the formation of carbonyl compounds. This reaction is significant because it offers a straightforward method to identify the structure of an unknown alkene by analyzing the carbonyl products.

• Each molecule of ozone can react with one double bond.
• Typically results in aldehydes or ketones, depending on the alkene type involved.
• Useful in the structural determination and degradation of complex organic molecules.

Carbonyl Compounds

Carbonyl compounds are a class of organic chemical compounds characterized by a carbon atom double-bonded to an oxygen atom ( C=O ). They play a vital role in the chemistry of organic reactions as intermediates and end products. These compounds are classified as either aldehydes or ketones:

• An aldehyde has at least one hydrogen atom attached to the carbonyl carbon. Formaldehyde, acetaldehyde, and benzaldehyde are common examples.
• In a ketone, the carbonyl carbon is bonded to two carbon groups. Acetone is one of the simplest and most common ketones.

Carbonyl compounds are known for their distinct reactivity, partaking in numerous reactions such as nucleophilic addition, oxidation, and reduction, making them essential in synthetic chemistry.

Alkenes

Alkenes are hydrocarbons containing at least one carbon-carbon double bond. This double bond is the defining characteristic of alkenes and provides them with unique chemical properties that distinguish them from other hydrocarbons such as alkanes. Key features of alkenes include:

• The presence of the C=C bond, which is more reactive than single C-C bonds found in alkanes.
• Alkenes follow a general formula CₙH₂ₙ , indicating their unsaturation compared to alkanes.
• They can undergo a variety of chemical reactions, including addition reactions, which are crucial in forming alcohols, halides, and other functional groups.

Because of their reactivity, alkenes serve as building blocks in the synthesis of more complex chemicals and are widely used in pharmaceuticals, plastics, and many other industries.

Chemical Reactions

Chemical reactions are processes in which substances convert into different substances. In the realm of organic chemistry, understanding the types, processes, and outcomes of these reactions is key to grasping how compounds react and transform. Key aspects of chemical reactions include:

• Reactants and Products: Reactants are substances that start a reaction, while products are substances formed as a result of the reaction.
• Mechanism: The detailed step-by-step process by which reactants transform into products. Various mechanisms exist depending on the type of reaction.
• Reactivity: This is influenced by the structure of the reactants, the presence of catalysts, temperature, and pressure.

One category of chemical reactions especially important in organic chemistry is addition reactions, such as those involving alkenes reacting with O₃ in ozonolysis. Understanding how reactions proceed helps in predicting reaction products and pathway selection in synthetic chemistry.