Question

Ozonolysis of mesitylene gives: (a) \(\mathrm{CH}_{3}-\mathrm{CO}-\mathrm{CHO}\) (b) CC(=O)C(C)=O (c) \(\mathrm{CHO}-\mathrm{CHO}\) (d) Both a, b

Short answer

None of the given options distinctly fit the expected ozonolysis outcome for mesitylene.

Step-by-step solution

Understand Reactant

Mesitylene, also known as 1,3,5-trimethylbenzene, is an aromatic hydrocarbon with three methyl groups attached to a benzene ring at the 1, 3, and 5 positions.

Define Ozonolysis

Ozonolysis is a reaction where ozone ( O3 ) cleaves the double bonds in alkenes or aromatic compounds to form carbonyl compounds. When applied to alkenes, ozonolysis typically breaks the C=C bonds and forms aldehydes or ketones.

Identify Cleavage Points

In mesitylene, consider the benzene ring undergoing ozonolysis. The ring structure breaks open at the points between the methyl groups and the carbon atoms they are connected to.

Form Intermediate Products

Once the benzene ring is cleaved, each segment forms carbonyl compounds. Given the positioning of the methyl groups, cleaving the bonds results in three separate acyl fragments.

Determine Final Products

For mesitylene, after ozonolysis, each segment forms an aldehyde or keto structure. The key expected products would be 3 molecules of acetic acid derivatives: acetone ( CH3COCH3 ).

Evaluate Options

Compare the end products of mesitylene ozonolysis to the options provided: (a) CH3COCHO - This is incorrect as it suggests only one carbonyl is formed. (b) CC(=O)C(C)=O - This implies the formation of diketone-like structure (incorrect for mesitylene). (c) CHOCHO - This represents glyoxal which is not relevant from mesitylene. (d) Both a, b - Option 'a' and 'b' taken together do not match the expected result. Thus no option is correct based purely on ozonolysis providing basic types of ketone-like products.

Key concepts

Mesitylene

Mesitylene, formally known as 1,3,5-trimethylbenzene, is an interesting compound with a unique structure. It belongs to a category of chemicals known as aromatic hydrocarbons. In mesitylene, the core structure is a benzene ring, which is common in aromatic compounds, but it has three methyl groups attached at the 1, 3, and 5 positions on the ring. This methyl group arrangement gives mesitylene some special properties:

• Stability: The presence of the methyl groups stabilizes the benzene ring due to the electron-donating effect, making mesitylene more robust against certain reactions compared to simple benzene.
• Volatility and Aroma: Like many aromatic compounds, mesitylene is known for its strong and often pleasant odor.

Mesitylene is widely used in research settings, particularly in studies involving organic synthesis, and serves as a versatile hydrocarbon in chemical reactions.

Aromatic hydrocarbon

The term 'aromatic hydrocarbon' refers to a specific class of compounds formed from more complex carbon ring structures, notably the benzene ring. Benzene, the simplest aromatic hydrocarbon, serves as a building block for more complex arrangements like mesitylene. Aromatic compounds are characterized by the following features:

• Ring structure: They contain a cyclical arrangement of carbon atoms, often with alternating single and double bonds (a concept known as conjugation).
• Aromaticity: This qualitative property arises from the stability provided by delocalized electrons above and below the plane of the ring, leading to unusual stability and reactivity patterns.
• Common Reactions: Aromatic hydrocarbons are involved in reactions like nitration, sulfonation, and other electrophilic substitution reactions. Ozonolysis, which breaks down aromatic rings into simpler substances, is just one way to transform aromatic compounds into other useful chemicals.

Aromatic hydrocarbons like mesitylene are foundational in making a plethora of materials and chemicals used in industry.

Carbonyl compounds

Carbonyl compounds are organic molecules characterized by a carbon atom double-bonded to an oxygen atom, represented as C=O. This functional group is a cornerstone of organic chemistry and is central to a variety of chemical reactions and properties:

• Reaction sites: The carbon atom in the carbonyl group is electrophilic, meaning it is attracted to electrons. This makes it reactive with nucleophiles, which are electron-rich species.
• Types: Major types of carbonyl compounds include aldehydes and ketones, which are important for many synthetic pathways in organic chemistry and industry.
• Formation: In ozonolysis, carbonyl compounds are typically formed by the cleavage of C=C double bonds in alkenes, leading to smaller, reactive fragments like formaldehyde or ketones.

These compounds are essential in biological systems and synthetic processes, making them critical to understanding chemical reactivity.

Aldehydes and ketones

Aldehydes and ketones are two subcategories of carbonyl compounds that share the C=O functional group. However, they differ in their specific structures and properties:

• Aldehydes: Represented by the general formula R-CHO, aldehydes have the carbonyl group at the end of a carbon chain. This position makes them particularly reactive in oxidation and condensation reactions.
• Ketones: Represented by R-CO-R', ketones have the carbonyl group within the carbon chain, often between two carbon atoms. This internal positioning gives them unique properties compared to aldehydes.
• Role in Ozonolysis: During ozonolysis, both aldehydes and ketones can be products, depending on the structure of the starting alkene. These carbonyl compounds are usually formed when double bonds are cleaved, breaking the larger molecule into smaller, stable fragments.

Aldehydes and ketones are integral to both biological systems and industrial applications. They are used in everything from flavoring to solvents and are essential ingredients in the synthesis of more complex organic molecules.