Question

The IUPAC name of \(\mathrm{CH}_{3} \mathrm{COCH}\left(\mathrm{CH}_{3}\right)_{2}\) is (a) 4 -methyl isopropyl ketone (b) 3 -methylbutan-2-one (c) isopropylmethyl ketone (d) 2 -methylbutan- 3 -one

Short answer

The IUPAC name is 3-methylbutan-2-one (option b).

Step-by-step solution

Identify the Functional Group

The given compound \( \mathrm{CH}_{3} \mathrm{COCH} \left( \mathrm{CH}_{3} \right)_{2} \) is a ketone, characterized by the presence of a carbonyl group \((C=O)\) attached to alkyl groups on both sides.

Determine the Longest Carbon Chain

Start numbering from the end nearest the ketone group. The longest continuous carbon chain containing the carbonyl group has 4 carbons, which is a butane chain.

Identify and Name Substituents

The substituent is a methyl group \((\mathrm{CH}_{3})\), attached to the third carbon of the butane chain.

Combine to Write the IUPAC Name

The IUPAC naming combines the information: the parent chain is butane with a ketone group (butanone), and there is a methyl group at the third position. Thus, the IUPAC name is 3-methylbutan-2-one.

Key concepts

Organic Chemistry

Organic chemistry is the study of the structure, properties, composition, reactions, and synthesis of carbon-containing compounds. These compounds often contain other elements such as hydrogen, oxygen, nitrogen, and others. In organic chemistry, the focus is on understanding how carbon atoms link together to form complex structures that manifest in a variety of organic molecules. These molecules are everywhere, from the sugars that fuel our bodies to the synthetic polymers that make our clothing.

• Organic compounds include a vast array of molecules, such as hydrocarbons and biomolecules.
• The versatility of carbon allows it to form stable bonds with many elements, leading to a diverse range of organic compounds.
• Organic chemistry is foundational in the development of many industries, including pharmaceuticals, petrochemicals, and food.

Learning organic chemistry opens doors to understanding the natural world and manipulating it for practical purposes.

Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic properties and chemical reactivities. They are the key determinants of the chemical behavior of organic compounds, and they help in the classification and naming of organic molecules.
In the context of the given exercise, the functional group present is a ketone.

• The presence of a carbonyl group \((\text{C=O})\) is what defines a ketone.
• In ketones, the carbonyl group is bonded to two carbon atoms, which differentiates them from aldehydes, where at least one side is a hydrogen.
• Functional groups are pivotal because they participate in reactions that transform the structure and nature of chemical substances.

Understanding functional groups is crucial as they inform the reactivity and interactions within molecules, dictating the nature of organic reactions.

Carbon Chain Identification

Identifying the carbon chain in a molecule is essential for determining its base structure and name. This involves finding the longest continuous chain of carbon atoms, which serves as the backbone of organic compounds.
For the problem at hand, identifying the longest carbon chain involved recognizing the four-carbon butane chain.

• Begin counting the chain closest to any functional groups present, as these are prioritized in naming.
• If there are substituents (additional groups) attached, note their position based on their proximity to functional groups.
• The length and nature of the carbon chain often determine the base name in IUPAC nomenclature, such as "butane" representing a four-carbon chain.

Correct identification of the carbon chain ensures that the structure of the molecule is accurately represented in its name.

Structural Isomerism

Structural isomerism occurs when molecules have the same molecular formula but different structural arrangements. This concept is important in organic chemistry because different structures can result in compounds with vastly different properties.
In analyzing the given compound, while the molecular formula might resemble others, the specific arrangement dictates its unique name and properties.

• Isomers can differ in the connectivity of atoms (chain isomers), the positions of functional groups (position isomers), or different functional groups altogether (functional isomers).
• Recognizing the type of isomerism helps chemists understand how structural change can affect physical and chemical properties.
• For example, only the specific arrangement described in the problem results in the compound being 3-methylbutan-2-one.

Understanding structural isomerism is crucial for identifying the correct compound among those with the same molecular formula.