Question

Draw structural formulas for (a) The eight alcohols with the molecular formula \(\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}\). (b) The eight aldehydes with the molecular formula \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}\). (c) The six ketones with the molecular formula \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}\). (d) The eight carboxylic acids with the molecular formula \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2}\). (e) The nine carboxylic esters with the molecular formula \(\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}\).

Short answer

Question: Identify the number of possible structural formulas for each class of organic compounds with the given molecular formulas: alcohols with \(\mathrm{C}_{5}\mathrm{H}_{12} \mathrm{O}\), aldehydes with \(\mathrm{C}_{6}\mathrm{H}_{12} \mathrm{O}\), ketones with \(\mathrm{C}_{6}\mathrm{H}_{12} \mathrm{O}\), carboxylic acids with \(\mathrm{C}_{6}\mathrm{H}_{12} \mathrm{O}_{2}\), and carboxylic esters with \(\mathrm{C}_{5}\mathrm{H}_{10} \mathrm{O}_{2}\). Answer: There are 8 possible alcohols, 8 possible aldehydes, 6 possible ketones, 8 possible carboxylic acids, and 9 possible carboxylic esters for the given molecular formulas.

Step-by-step solution

Alcohols

Start by drawing all possible structural isomers of \(\mathrm{C}_{5}\mathrm{H}_{12}\), where the base carbon chains can be linear as well as branched. Then, replace one hydrogen in each isomer with an -OH group, which is the functional group for alcohols. There are eight different alcohols possible for the molecular formula \(\mathrm{C}_{5}\mathrm{H}_{12} \mathrm{O}\).

Aldehydes

Draw all possible structural isomers of \(\mathrm{C}_{6}\mathrm{H}_{12}\). Replace one terminal hydrogen at the end of the carbon chain with an -CHO group, which is the functional group for aldehydes. There are eight different aldehydes possible for the molecular formula \(\mathrm{C}_{6}\mathrm{H}_{12} \mathrm{O}\).

Ketones

Draw all possible structural isomers of \(\mathrm{C}_{6}\mathrm{H}_{12}\). Replace one internal hydrogen with a =O group, which is the functional group for ketones. A ketone cannot be at the end of the carbon chain since it needs to have a carbon atom attached to both sides of the carbonyl group. There are six different ketones possible for the molecular formula \(\mathrm{C}_{6}\mathrm{H}_{12} \mathrm{O}\).

Carboxylic Acids

Draw all possible structural isomers of \(\mathrm{C}_{6}\mathrm{H}_{12}\). Replace one terminal hydrogen at the end of the carbon chain with a -COOH group, which is the functional group for carboxylic acids. There are eight different carboxylic acids possible for the molecular formula \(\mathrm{C}_{6}\mathrm{H}_{12} \mathrm{O}_{2}\).

Carboxylic Esters

Start by drawing all possible structural isomers of \(\mathrm{C}_{5}\mathrm{H}_{10}\mathrm{O}_{2}\) for carboxylic esters, which are a combination of carboxylic acids and alcohols. The functional group for carboxylic esters is -COOR, where R can be any alkyl group. Break the parent compound into two parts: one having the carboxylate ion (-COO-) and the other having the alkyl group (-R). There are nine different carboxylic esters possible for the molecular formula \(\mathrm{C}_{5}\mathrm{H}_{10} \mathrm{O}_{2}\).

Key concepts

Functional Group Chemistry

When diving into the world of organic chemistry, one of the essential concepts to understand is functional group chemistry. A functional group is a specific group of atoms within a molecule that is responsible for the characteristic chemical reactions of that molecule. These groups can modify the usual reactions of hydrocarbons by providing new sites of reactivity.

Different functional groups impart unique properties to the molecules and can significantly alter the molecule's behavior in chemical reactions. For example, alcohols contain the hydroxyl (-OH) group, which makes them polar and capable of forming hydrogen bonds. Aldehydes and carboxylic acids both feature a carbonyl group (C=O), but aldehydes have it at the end of the carbon chain (forming -CHO), while carboxylic acids have an additional hydroxyl group attached to the carbon, making it -COOH.

Understanding how to identify and manipulate these functional groups is crucial for predicting how a molecule will interact in various environments, which is a fundamental skill in organic synthesis and analysis. By learning about functional groups, students begin to see the vast diversity of organic compounds that can be built from a seemingly limited set of building blocks.

Drawing Structural Formulas

Structural formulas are representations of molecules that show not only the types and quantities of atoms but also their arrangement within the molecule. Drawing these formulas is vital for visualizing and understanding the molecular structure and plays a crucial role when studying isomerism in organic compounds.

To ensure that students grasp the concepts behind drawing structural formulas, it’s important to start with the basics of bonding and molecule geometry. As they progress, they can then consider things like functional groups and how they alter the chemical and physical properties of a molecule.

Tips for Drawing Accurate Structural Formulas

• Begin with the skeletal structure showing the carbon chain or ring.
• Identify and add in the functional groups at their appropriate locations.
• Use straight lines to denote bonds, with the correct angles to suggest the geometry around carbon atoms.
• Ensure the correct number of hydrogen atoms are included to satisfy the valency of each carbon.

By practicing these steps, students not only learn how to accurately reflect the molecular structure but also become more comfortable with predicting the physical and chemical behavior of the molecules they're studying.

Organic Compounds Isomerism

Isomerism in organic chemistry is the phenomenon where compounds with the same molecular formula have different structural formulas. This occurs because the atoms can be arranged in different ways. There are several types of isomerism, but structural isomerism is one of the most fundamental and important to understand. It highlights how the arrangement of atoms impacts the properties and reactivity of molecules.

In the given exercise, drawing structural isomers involves creatively rearranging carbon chains and identifying various locational possibilities for functional groups. For instance, carboxylic esters, which feature the -COOR group, can have multiple isomer forms based on where this group is attached and how the rest of the molecule is configured.

Understanding Isomerism

• Structural isomers have the same molecular formula but differ in how atoms are connected.
• Positional isomers have functional groups in different locations on the carbon chain.
• Functional isomers have the same atoms but in different functional groups, leading to distinctive properties.

Grasping these concepts not only aids in understanding organic compound diversity but is also crucial for applications in industries like pharmaceuticals and materials science, where specific isomers can have strikingly different effects or uses.