Question

Write condensed structures of the following compounds: (a) 3 -methylbutanal (c) 2 -chloropropanoic acid (b) 4 -methyloctan- 2 -one (d) 1 -methylethylethanoate

Short answer

The condensed structures are: (a) CH3-CH2-CH(CH3)-CHO, (c) CH3-CH(Cl)-COOH, (b) CH3-CH2-CO-CH2-CH(CH3)-CH2-CH2-CH3, and (d) CH3-COO-CH(CH3)-CH3.

Step-by-step solution

Identify the Functional Group and Carbon Chain for 3-methylbutanal

Locate the aldehyde group, which is present at the end of the carbon chain, due to the 'anal' suffix. Recognize that 'but' refers to a four-carbon chain, and '3-methyl' indicates a methyl group attached to the third carbon of the chain.

Draw the Condensed Structure for 3-methylbutanal

Start with the four-carbon chain with the aldehyde at the end. Then add a methyl group on the third carbon: CH3-CH2-CH(CH3)-CHO.

Identify the Functional Group and Carbon Chain for 2-chloropropanoic acid

Note the carboxylic acid group from 'anoic acid' indicating the presence of COOH at the end of the chain. 'Propan' signifies a three-carbon chain, and '2-chloro' indicates a chlorine atom attached to the second carbon.

Draw the Condensed Structure for 2-chloropropanoic acid

Begin with the three-carbon chain with COOH on one end. Attach a chlorine atom to the second carbon: CH3-CH(Cl)-COOH.

Identify the Functional Group and Carbon Chain for 4-methyloctan-2-one

The 'one' suffix denotes a ketone, with the oxygen double-bonded to the second carbon. 'Octan' refers to an eight-carbon main chain, and '4-methyl' indicates a methyl group on the fourth carbon.

Draw the Condensed Structure for 4-methyloctan-2-one

Start with the eight-carbon chain. Place a ketone group at the second position and a methyl group on the fourth carbon: CH3-CH2-CO-CH2-CH(CH3)-CH2-CH2-CH3.

Identify the Functional Group and Carbon Chain for 1-methylethylethanoate

Recognize 'ethanoate' as the ester group COO, connected to a two-carbon (ethyl) parent structure. '1-methylethyl' is the substituent group attached to the oxygen, which is a two-carbon chain with a methyl on the first carbon.

Draw the Condensed Structure for 1-methylethylethanoate

Construct the ester functional group with an ethyl group: CH3-COO. Add the 1-methylethyl group to the oxygen atom of the ester: CH3-COO-CH(CH3)-CH3.

Key concepts

Functional Groups in Organic Chemistry

Understanding functional groups is pivotal for mastering organic chemistry. Functional groups are specific atoms or groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.

Each functional group has a particular set of properties and reactivity patterns. For example, aldehydes, such as in 3-methylbutanal, have the functional group -CHO, which is typically found at the end of a carbon chain. Carboxylic acids like 2-chloropropanoic acid contain the carboxyl group -COOH. Ketones, such as in 4-methyloctan-2-one, have a carbonyl group (-CO-) located within the carbon chain, not at the end. Lastly, esters like 1-methylethylethanoate have a -COO- group connecting two hydrocarbon chains.

Identifying these functional groups provides insight into the behavior of the molecule, its reactive sites, and its solubility. When approaching a chemistry problem, looking for these distinct functional groups can significantly simplify the process of understanding and drawing the chemical structure.

Carbon Chain Identification

The carbon backbone is the foundation of any organic molecule, and the ability to identify carbon chains is a fundamental skill in organic chemistry. Carbon chains can be straight, branched, or even form rings, and they are named based on the number of carbons they contain.

The prefix 'meth-' indicates one carbon, 'eth-' two carbons, 'prop-' three carbons, and so on. Identifying the length of the carbon chain helps us establish the basic skeleton of the molecule. In exercises involving condensed chemical structures, like the example of 3-methylbutanal, the term 'but' points to a four-carbon chain. Similarly, 'octan' in 4-methyloctan-2-one refers to an eight-carbon chain. Once we know the length, we can determine the positions of other substituents or functional groups, such as a methyl group or a chlorine atom, as indicated by number prefixes in the compound's name.

Drawing Organic Molecules

Drawing organic molecules, such as condensed chemical structures, is a skill that allows chemists to communicate complex information efficiently. These structural formulas provide a way to represent the 3D arrangements of atoms in a molecule on a two-dimensional surface.

To draw condensed chemical structures, it's imperative first to identify the main carbon chain and its functional groups, as seen in the step-by-step solutions for molecules like 3-methylbutanal or 1-methylethylethanoate. Then, starting with the main carbon chain, substituents are added at their respective carbon atoms. For example, a chlorine atom would be shown as '-Cl' and a methyl group as '-CH₃'. It's essential to regard the correct placement of functional groups to accurately depict the molecule's structure. By mastering these representations, students can better visualize how molecules may interact and react in various scenarios, an essential aspect of understanding organic chemistry.