Question

Draw a structural formula for each compound. (a) Phenylacetic acid (b) 4-Aminobutanoic acid (c) 3-Chloro-4-phenylbutanoic acid (d) Propenoic acid (acrylic acid) (e) (Z)-3-Hexenedioic acid (f) 2-Pentynoic acid (g) Potassium phenylacetate (h) Sodium oxalate (i) 2-Oxocyclohexanecarboxylic acid (j) 2,2-Dimethylpropanoic acid

Short answer

Question: Draw the structural formulas of the following compounds: (a) Phenylacetic acid (b) 4-Aminobutanoic acid (c) 3-Chloro-4-phenylbutanoic acid (d) Propenoic acid (acrylic acid) (e) (Z)-3-Hexenedioic acid (f) 2-Pentynoic acid (g) Potassium phenylacetate (h) Sodium oxalate (i) 2-Oxocyclohexanecarboxylic acid (j) 2,2-Dimethylpropanoic acid Answer: (a) Phenylacetic acid: C6H5-CH2-COOH (b) 4-Aminobutanoic acid: H2N-(CH2)3-COOH (c) 3-Chloro-4-phenylbutanoic acid: Cl-CH2-CH(C6H5)-CH2-COOH (d) Propenoic acid (acrylic acid): CH2=CH-COOH (e) (Z)-3-Hexenedioic acid: HOOC-(CH2)2-CH=CH-(CH2)COOH (double bond with Z configuration) (f) 2-Pentynoic acid: CH3-C≡C-CH2-COOH (g) Potassium phenylacetate: K+[C6H5-CH2-COO-] (h) Sodium oxalate: Na+[OOC-COO-]Na+ (i) 2-Oxocyclohexanecarboxylic acid: COOH-CH2-CH2-(C=O)-CH2-CH2-cyclohexane (j) 2,2-Dimethylpropanoic acid: (CH3)2-CH-COOH

Step-by-step solution

Identify the functional group and main chain

Phenylacetic acid has a phenyl group and a carboxylic acid group. The main chain is composed of two carbons.

Draw the structural formula

The structural formula for phenylacetic acid is C6H5-CH2-COOH. (b) 4-Aminobutanoic acid

Identify the functional group and main chain

4-Aminobutanoic acid has an amino group and a carboxylic acid group. The main chain is composed of four carbons.

Draw the structural formula

The structural formula for 4-Aminobutanoic acid is H2N-(CH2)3-COOH. (c) 3-Chloro-4-phenylbutanoic acid

Identify the functional group and main chain

3-Chloro-4-phenylbutanoic acid has a carboxylic acid group, a chloro group, and a phenyl group. The main chain is composed of four carbons.

Draw the structural formula

The structural formula for 3-Chloro-4-phenylbutanoic acid is Cl-CH2-CH(C6H5)-CH2-COOH. (d) Propenoic acid (acrylic acid)

Identify the functional group and main chain

Propenoic acid has a carboxylic acid group and an alkene group. The main chain is composed of three carbons.

Draw the structural formula

The structural formula for propenoic acid is CH2=CH-COOH. (e) (Z)-3-Hexenedioic acid

Identify the functional group and main chain

(Z)-3-Hexenedioic acid has two carboxylic acid groups and an alkene group. The main chain is composed of six carbons.

Draw the structural formula

The structural formula for (Z)-3-Hexenedioic acid is HOOC-(CH2)2-CH=CH-(CH2)COOH (the double bond having Z configuration). (f) 2-Pentynoic acid

Identify the functional group and main chain

2-Pentynoic acid has a carboxylic acid group and an alkyne group. The main chain is composed of five carbons.

Draw the structural formula

The structural formula for 2-Pentynoic acid is CH3-C≡C-CH2-COOH. (g) Potassium phenylacetate

Identify the functional group and main chain

Potassium phenylacetate has a phenyl group and a carboxylate anion. The main chain is composed of two carbons.

Draw the structural formula

The structural formula for potassium phenylacetate is K+[C6H5-CH2-COO-]. (h) Sodium oxalate

Identify the functional group and main chain

Sodium oxalate has two carboxylate anions. The main chain is composed of two carbons.

Draw the structural formula

The structural formula for sodium oxalate is Na+[OOC-COO-]Na+. (i) 2-Oxocyclohexanecarboxylic acid

Identify the functional group and main chain

2-Oxocyclohexanecarboxylic acid has a carboxylic acid group and a ketone group in a cyclohexane ring.

Draw the structural formula

The structural formula for 2-Oxocyclohexanecarboxylic acid is COOH-CH2-CH2-(C=O)-CH2-CH2-cyclohexane. (j) 2,2-Dimethylpropanoic acid

Identify the functional group and main chain

2,2-Dimethylpropanoic acid has a carboxylic acid group and two methyl groups. The main chain is composed of three carbons.

Draw the structural formula

The structural formula for 2,2-Dimethylpropanoic acid is (CH3)2-CH-COOH.

Key concepts

Carboxylic Acids

Carboxylic acids are one of the fundamental functional groups in organic chemistry, represented by the general formula R-COOH, where R represents an alkyl or aryl group. These compounds are characterized by the presence of a carboxyl group, which consists of a carbon atom double-bonded to an oxygen atom (carbonyl group) and a hydroxyl group. The presence of both electronegative oxygen atoms lends carboxylic acids their acidic properties.

For instance, phenylacetic acid (C6H5-CH2-COOH) includes a phenyl group (the R) bonded to the COOH group. Carboxylic acids are versatile in chemical reactions, participating in numerous biochemical processes and industrial applications, such as the manufacturing of plastics and pharmaceuticals.

Understanding carboxylic acids is crucial for students, as they are pivotal in creating larger organic molecules. In exercises, identifying the COOH group is the initial step. Knowing how the COOH group interacts with different R groups is essential for predicting the chemical behavior of these molecules.

Functional Groups in Organic Molecules

Functional groups are specific clusters of atoms within molecules that have characteristic properties and chemical reactivities. Organic chemistry is structured around the concept of functional groups, as they dictate how a molecule will function in a chemical reaction.

Key functional groups in organic chemistry include hydroxyl (OH), carbonyl (C=O), carboxyl (COOH), amino (NH2), and halides (such as Cl, Br, or I). Each functional group has a unique set of properties that can alter the molecule's physical and chemical behavior. For example, 4-Aminobutanoic acid includes both an amino (–NH2) group and a carboxyl (–COOH) group, contributing to its distinct reactivity and solubility compared to hydrocarbons without these groups.

When approaching an exercise, students should first identify and mark all functional groups. This identification can immensely simplify the process of understanding, predicting, and solving chemical reactions associated with the molecule at hand.

Drawing Organic Structures

Drawing organic structures is a fundamental skill in organic chemistry that allows students to visualize and comprehend the molecular architecture of compounds. There are several methods for drawing these structures, such as displaying bonds as lines and atoms as letters.

For instance, in drawing compounds like propenoic acid, it's important to not only identify the carboxylic acid group but also to correctly depict the placement of the double bond in the alkene group. Likewise, for sodium oxalate (Na+[OOC-COO-]Na+), illustrating the ionic nature of the sodium cations and the oxalate anions is vital.

Practicing the skill of drawing organic structures begins with mastering the ability to identify functional groups and the main chain of carbon atoms. Modifying those structures to include double bonds, rings, or other complexities comes after grasping the basics. Drawing exercises help reinforce the spatial and geometrical understanding of molecules, which is crucial for appreciating organic chemistry's three-dimensional nature.