Problem 84 - Chemistry: The Central Science in SI Units, Global Edition

Question

Consider the following organic substances: ethylethanoate, ethylmethylether, hexanol, and propanone. (a) Which of these molecules contains three carbons? (b) Which of these molecules contain a \(\mathrm{C}=\) O group?

Step-by-Step Solution

Answer

(a) Ethylmethylether and Propanone contain three carbons. (b) Ethylethanoate and Propanone contain a \(\mathrm{C}=\) O group.

Step 1: Identify molecular structures of the organic substances

Ethylethanoate (also called Ethyl Acetate): CH₃COOCH₂CH₃ Ethylmethylether (also called Ethyl Methyl Ether): CH₃CH₂OCH₃ Hexanol: CH₃(CH₂)₄CH₂OH Propanone (also called Acetone): CH₃COCH₃

Step 2: Determine the molecules containing three carbons

We will count the total number of carbon atoms in each molecule. Ethylethanoate: 4 carbon atoms Ethylmethylether: 3 carbon atoms Hexanol: 6 carbon atoms Propanone: 3 carbon atoms Answer (a): Ethylmethylether and Propanone contain three carbons.

Step 3: Identify the molecules containing \(\mathrm{C}=\) O group

We will look for the presence of \(\mathrm{C}=\) O group in each molecule. Ethylethanoate: It has a \(\mathrm{C}=\text{O}\) group in the COO fragment. Ethylmethylether: There is no \(\mathrm{C}=\) O group present. Hexanol: There is no \(\mathrm{C}=\) O group present. Propanone: It contains \(\mathrm{C}=\) O group in the COCH₃ fragment. Answer (b): Ethylethanoate and Propanone contain a \(\mathrm{C}=\) O group.

Key Concepts

Carbon Structures

In organic chemistry, carbon structures are the foundation of molecules. These structures consist of carbon atoms bonded together. The ability of carbon atoms to form four bonds makes them unique. It allows the formation of a variety of structures. These include branches, chains, and rings that form the basis of organic compounds.

• Chains: Carbon atoms can connect in long straight or branched chains. This flexibility is why carbon is the backbone of organic life.
• Rings: Carbon can also form ring structures, which adds to its versatile nature.

Carbon structures can vary in the number of carbon atoms. In the given exercise, we see different molecules with a varying number of carbons. For instance, ethylmethylether and propanone both contain 3 carbon atoms. The size and shape of carbon structures can define the properties and reactivity of the molecule.

Carbonyl Group

The carbonyl group is a functional group characterized by a carbon atom double-bonded to an oxygen atom, denoted as \( \mathrm{C}=\mathrm{O} \). This group is significant in chemistry, influencing the reactivity and properties of molecules.

• Polar Nature: The \( \mathrm{C}=\mathrm{O} \) bond is polar, with oxygen being more electronegative, affecting its reactivity.
• Occurrence: It is found in aldehydes, ketones, esters, and amides.

Within the exercise, ethylethanoate and propanone feature this group. Ethylethanoate has it in the COO fragment, while propanone has it in the COCH₃ fragment. These groups help define the compound's chemical behavior, such as reactivity to other substances.

Organic Molecules Identification

Identifying organic molecules entails analyzing their structure to determine essential functional groups and constituent atoms. This helps categorize and differentiate compounds by their chemical characteristics.

• Carbon Count: Counting carbon atoms aids in identifying and classifying the molecular structure. In the exercise, ethylmethylether and propanone were noted to each contain three carbon atoms.
• Functional Groups: Recognizing key functional groups like the \( \mathrm{C}=\mathrm{O} \) group provides insight into reactivity and potential interactions. Ethylethanoate and propanone were found containing this group.
• Naming Conventions: Understanding naming helps match structures to the IUPAC or common names, which was demonstrated in the molecule naming in the exercise.

By examining these aspects, students can accurately identify various organic compounds and understand their potential chemical reactions.