Question

Draw the molecular structure for (a) an aldehyde that is an isomer of acetone, (b) an ether that is an isomer of 1-propanol.

Short answer

The aldehyde isomer of acetone is propanal, with the structure: H H H | | | C-C-C=O | | H H The ether isomer of 1-propanol is methoxyethane (ethyl methyl ether), with the structure: H H H | | | H-C-O-C-C | | H H

Step-by-step solution

Identify the formula of the given compounds (acetone and 1-propanol)

Acetone is a ketone with the molecular formula \(C_3H_6O\). Its structure includes a carbonyl group (C=O) bonded to two other carbons. 1-propanol, on the other hand, is an alcohol with the molecular formula \(C_3H_8O\). Its structure consists of an oxygen atom bonded to a carbon atom and a hydrogen atom (a hydroxyl group, OH).

Determine the possible aldehyde isomer for acetone

An aldehyde has a carbonyl group (C=O) at the end of the carbon chain. Since the molecular formula of acetone is \(C_3H_6O\), the aldehyde isomer must also have the same molecular formula. By converting the ketone carbonyl group in acetone to an aldehyde, we can determine the structure of the aldehyde isomer. The resulting aldehyde isomer is propanal, which has the chemical formula \(C_3H_6O\) and the structure: H-C(H)=O.

Draw the molecular structure of the aldehyde isomer of acetone (Propanal)

Place the carbonyl group at the end of the three-carbon chain. The structure of propanal is as follows: H H H | | | C-C-C=O | | H H

Determine the possible ether isomer for 1-propanol

An ether has an oxygen atom connected to two alkyl (carbon) groups. Since the molecular formula of 1-propanol is \(C_3H_8O\), the ether isomer must also have the same molecular formula. Replace the hydroxyl group in 1-propanol with an oxygen atom, connecting two carbon atoms. The resulting ether isomer is methoxyethane (ethyl methyl ether), which has the chemical formula \(C_3H_8O\) and the structure: H-C-O-C.

Draw the molecular structure of the ether isomer of 1-propanol (Methoxyethane)

Connect the oxygen atom between a methyl (CH3) and an ethyl (CH2-CH3) group. The structure of methoxyethane is as follows: H H H | | | H-C-O-C-C | | H H

Key concepts

Aldehydes

Aldehydes are a group of organic compounds characterized by having a carbonyl group, which is a carbon double-bonded to an oxygen, positioned at the end of a carbon chain. This unique placement distinguishes aldehydes from other compounds with carbonyl groups, like ketones, where the carbonyl group is within the carbon chain.
Aldehydes are often known for their distinctive, often pleasing aromas, and they are widely used in the fragrance industry.
Given their simple structure, aldehydes like formaldehyde and acetaldehyde are widely utilized in industrial processes and the production of resins and plastics. Propanal is a specific example of an aldehyde that is isomeric with acetone, featuring the same molecular formula, but a different arrangement of atoms. Isomers are compounds with identical formulas but different arrangements, resulting in distinct properties.

Ethers

Ethers are a class of organic compounds where an oxygen atom is bonded to two alkyl or aryl groups, which are carbon-containing side chains.
The general formula for an ether is R-O-R', where R and R' represent the alkyl groups. The oxygen atom in ethers acts as a bridge between these two groups, lending ethers their characteristic structural and functional properties.

• Unlike alcohols, ethers lack a hydroxyl group (OH), which significantly influences their reactivity and solubility.
• Ethers are widely used as solvents due to their relative inertness and ability to dissolve a wide range of chemical substances.

In the context of isomerism, ethers can share a molecular formula with alcohols, as shown in methoxyethane being an isomer of 1-propanol. Despite having the same chemical formula, their structural differences lead to distinct physical and chemical properties.

Molecular Structure

The molecular structure of a compound is a depiction of how its atoms are arranged in space and joined by chemical bonds. Each type of molecule has a unique structural blueprint that determines its chemical behavior and physical properties.
The skeletal structure of an organic compound usually highlights the backbone of carbon atoms and key functional groups, such as carbonyl, hydroxyl, or ether linkages.

• Molecular structures can be represented in various ways, including line-angle drawings, 3D models, or empirical formulas.
• The arrangement and connection of atoms impact key attributes like boiling point, melting point, and reactivity.

Understanding molecular structure is crucial, particularly in recognizing isomers, which, although having the same number of each type of atom, differ in the arrangement of these atoms, greatly affecting their functionality.

Acetone

Acetone, scientifically known as propanone, is the simplest and smallest ketone characterized by a central carbonyl group flanked by methyl groups on either side.
Its chemical formula is \(C_3H_6O\), illustrating an efficient and compact molecular structure. Acetone is a colorless, volatile, and flammable liquid renowned for being a common solvent in industries and laboratories, as well as in the production of plastics.

• Due to its excellent solubility for many organic substances, acetone is frequently used for cleaning purposes, including removing paints and varnishes.

Understanding acetone’s structural composition helps in identifying its isomeric forms, such as propanal, which retains the same molecular formula but exhibits a different structure and consequently distinct properties.

1-Propanol

1-Propanol, also known as n-propyl alcohol, is an alcohol with the molecular formula \(C_3H_8O\). It belongs to the class of alcohols, distinguished by the presence of a hydroxyl (OH) group attached to its carbon chain.
In 1-propanol, the OH group is positioned at the first carbon of the chain, resulting in its name.

• As a member of the alcohol family, 1-propanol is miscible with water, characterized by a sweet odor and used in the production of solvents, pharmaceuticals, and cosmetics.
• The positioning of its hydroxyl group affects its boiling point, solubility, and reactivity.

The concept of isomerism is crucial here as it possesses the same molecular formula as methoxyethane but differs in its structural configuration, leading to different chemical properties and uses.