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Ch.14 Carboxylic Acids, Esters, Amines, and Amides
Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 13th Edition
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook
Chapter 14, Problem 49

Draw the condensed structural formulas and write the IUPAC names for two structural isomers of the carboxylic acids that have the molecular formula C4H8O2.

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Step 1: Understand the problem. The molecular formula C4H8O2 represents a carboxylic acid, which contains a carboxyl group (-COOH). Structural isomers are compounds with the same molecular formula but different connectivity of atoms. We need to draw two different structures and name them using IUPAC rules.
Step 2: Start with the first isomer. Place the carboxyl group (-COOH) at the end of a straight chain of four carbon atoms. This gives a structure with the carboxyl group attached to the first carbon. Write the condensed structural formula as CH3CH2CH2COOH.
Step 3: Name the first isomer. According to IUPAC rules, the longest chain containing the carboxyl group is four carbons long, so the base name is 'butanoic acid.' Since there are no substituents, the name is simply 'butanoic acid.'
Step 4: Create the second isomer by rearranging the carbon chain. Move one carbon from the main chain to form a branched structure. For example, place the carboxyl group on a three-carbon chain with a methyl group (-CH3) as a branch. The condensed structural formula is (CH3)2CHCOOH.
Step 5: Name the second isomer. The longest chain containing the carboxyl group is three carbons long, so the base name is 'propanoic acid.' The methyl group is a substituent on the second carbon. The IUPAC name is '2-methylpropanoic acid.'

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Carboxylic Acids

Carboxylic acids are organic compounds characterized by the presence of one or more carboxyl groups (-COOH). They are known for their acidic properties and are commonly found in various biological and chemical processes. The general formula for carboxylic acids is R-COOH, where R represents a hydrocarbon chain. Understanding their structure is essential for identifying isomers and naming them according to IUPAC conventions.
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Structural Isomers

Structural isomers are compounds that share the same molecular formula but differ in the arrangement of atoms within the molecule. This can lead to variations in physical and chemical properties. For the molecular formula C4H8O2, there can be multiple structural isomers, including variations in the position of the carboxyl group or the arrangement of carbon chains. Recognizing these differences is crucial for drawing accurate structural formulas.
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IUPAC Nomenclature

IUPAC nomenclature is a systematic method for naming chemical compounds based on their structure and functional groups. For carboxylic acids, the naming convention typically involves identifying the longest carbon chain containing the carboxyl group and using the suffix '-oic acid.' Understanding IUPAC rules is vital for correctly naming the structural isomers of carboxylic acids derived from the same molecular formula.
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