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 \(\mathrm{C}=\mathrm{O}\) group?

Short answer

(a) Ethylmethylether, Propanone. (b) Ethylethanoate, Propanone.

Step-by-step solution

Identify the Structure of Ethylethanoate

Ethylethanoate, also known as ethyl acetate, has the structure: \( \mathrm{CH_3COOC_2H_5} \). It contains four carbon atoms.

Identify the Structure of Ethylmethylether

Ethylmethylether has the structure: \( \mathrm{C_2H_5OCH_3} \). It contains three carbon atoms.

Identify the Structure of Hexanol

Hexanol is an alcohol with the structure: \( \mathrm{C_6H_{13}OH} \). It contains six carbon atoms.

Identify the Structure of Propanone

Propanone, also known as acetone, has the structure: \( \mathrm{CH_3COCH_3} \). It contains three carbon atoms and a carbonyl (\( \mathrm{C} = \mathrm{O} \)) group.

Determine Molecules with Three Carbons

Comparing the carbon atoms in each molecule, ethylmethylether and propanone each have three carbons.

Determine Molecules with a \( \mathrm{C} = \mathrm{O} \) Group

Among the molecules, ethylethanoate and propanone contain a carbonyl group (\( \mathrm{C} = \mathrm{O} \)).

Key concepts

Molecular Structure

Understanding the molecular structure of organic compounds is essential for grasping organic chemistry. A molecule's structure refers to the formal arrangement of atoms to form a particular shape. This structure dictates the physical and chemical properties of the molecule. Simply put, it's like a blueprint for how atoms are connected, the types of chemical bonds present, and the spatial relationships between atoms.
In the context of our discussion, ethylethanoate, ethylmethylether, hexanol, and propanone each have distinct structural formulas. By analyzing these formulas, one can deduce how the atoms in each molecule are arranged, giving insight into functionality and reactivity.

Functional Groups

Functional groups are key to understanding organic molecules. They are specific clusters of atoms within molecules that dictate how the molecule will react chemically. Functional groups are responsible for the characteristic reactions of organic compounds. For example, knowing that an -OH group is characteristic of alcohols helps in identifying and predicting alcohol reactions.
In our molecules:

• Ethylethanoate and propanone both contain carbonyl groups, affecting their reactivity.
• Hexanol contains a hydroxyl (-OH) group, classifying it as an alcohol with specific properties.
• Ethylmethylether includes an ether group, influencing its solubility and boiling point.

This classification helps in predicting possible chemical reactions and the environment where these compounds can function.

Carbonyl Group

The carbonyl group is a functional moiety seen in compounds like aldehydes and ketones. It consists of a carbon atom double-bonded to an oxygen atom (\( \mathrm{C} = \mathrm{O} \)). Its unique electronic properties make it a central point for chemical reactions, such as nucleophilic addition.
In our example substances, propanone (acetone) is known for its carbonyl group, which lies in the middle of the molecule, classifying it as a ketone. This group makes these compounds polar and often reactive. Additionally, ethylethanoate contains a carbonyl group associated with an ester linkage, giving distinct characteristics.

Ether

An ether is a class of organic compounds characterized by an oxygen atom connected to two alkyl or aryl groups. In simple terms, the ether group is represented by -O- and it's quite stable due to its low reactivity.
For instance, ethylmethylether showcases this structure with an oxygen atom bonded to both an ethyl group and a methyl group. This structure provides the compound with unique properties such as lower boiling points compared to alcohols of similar molecular weight and relative inertness under some conditions. Ethers are often considered non-polar due to their symmetrical structure, making them excellent solvents for many organic reactions.

Alcohol

Alcohols are organic compounds primarily recognized by the presence of a hydroxyl group (-OH) attached to a carbon atom. This hydroxyl group makes alcohols highly versatile, impacting their boiling points, solubility, and reactivity.
Hexanol is an example of an alcohol, presented with six carbon atoms and a single hydroxyl group. This -OH group allows hydrogen bonding, which significantly increases the boiling and melting points relative to other compounds. Because of this group, alcohols are often soluble in water and can engage in acid-base reactions, making them integral to numerous chemical processes.

Carbon Atoms

Carbon atoms serve as the backbone of organic chemistry, capable of forming four covalent bonds and creating complex structures like chains, rings, and branches. The unique ability of carbon to catenate (form chains) is unmatched.
In ethylethanoate, ethylmethylether, hexanol, and propanone, carbon atom counts vary, influencing their properties and classifications. For instance:

• Compounds like ethylmethylether and propanone featuring three carbon atoms can often be manipulated into various structures suitable for different reactions.
• Hexanol, with six carbon atoms, shows how varied carbon chain lengths affect properties such as solubility and volatility.

Thus, understanding the number and arrangement of carbon atoms in these molecules is crucial for predicting their behavior in organic reactions.