Problem 6 - Chemistry Matter and Change

Question

Define functional group and name the group present in each of the following structures. Name the type of organic compound each substance represents. \begin{equation} \begin{array}{l}{\text { a. } \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}} \\ {\mathrm{b} . \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{F}} \\\ {\mathrm{c} \cdot \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}}\end{array} \end{equation}

Step-by-Step Solution

Answer

a: Alcohol with hydroxyl group, b: Haloalkane with fluoro group, c: Amine with amino group.

Step 1: Define Functional Group

A functional group is a specific group of atoms within a molecule that is responsible for certain characteristic chemical reactions of that molecule. Functional groups are crucial in organic chemistry as they define the class of the molecule and its reactivity.

Step 2: Identify Functional Group in a.

The structure given is \( \text{CH}_3\text{CH}_2\text{CH}_2\text{OH} \). In this structure, the \( -\text{OH} \) group is present, which is known as the hydroxyl group, typically found in alcohols.

Step 3: Identify Type of Organic Compound for a.

The presence of the hydroxyl group \( -\text{OH} \) in \( \text{CH}_3\text{CH}_2\text{CH}_2\text{OH} \) classifies this molecule as an alcohol.

Step 4: Identify Functional Group in b.

The structure given is \( \text{CH}_3\text{CH}_2\text{F} \). The \( -\text{F} \) (fluoro) group is present, which belongs to the class of organohalides (specifically, it is a haloalkane).

Step 5: Identify Type of Organic Compound for b.

With the presence of the fluoro group \( -\text{F} \), \( \text{CH}_3\text{CH}_2\text{F} \) is categorized as a haloalkane.

Step 6: Identify Functional Group in c.

The structure given is \( \text{CH}_3\text{CH}_2\text{NH}_2 \). The \( -\text{NH}_2 \) group is present, known as an amino group, common in amines.

Step 7: Identify Type of Organic Compound for c.

The presence of the amino group \( -\text{NH}_2 \) in \( \text{CH}_3\text{CH}_2\text{NH}_2 \) identifies this molecule as an amine.

Key Concepts

Alcohol

Alcohol is an important category of organic compounds. It can be identified by the presence of a hydroxyl group, which is represented as \(-\text{OH}\). When this group is attached to a carbon atom in an organic molecule, it gives the molecule properties typical of alcohols.Some key characteristics of alcohols include:

• Alcohols are typically polar due to the hydroxyl group, allowing them to form hydrogen bonds with other alcohol molecules or water. This generally leads to higher boiling points compared to other organic compounds of similar molar mass.
• Their solubility in water decreases as the length of the carbon chain increases, due to the increase in nonpolar characteristics.
• Alcohols are often used as solvents and in perfumes but are most commonly known for their role in beverages.

An example of an alcohol is \(\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}\), known as propanol. Here, the \(-\text{OH}\) group plays a critical role in the compound's chemical reactions and overall behavior.

Haloalkane

Haloalkanes, also known as alkyl halides, are organic compounds where one or more halogen atoms are attached to an alkane. In these compounds, halogens such as fluorine, chlorine, bromine, or iodine replace hydrogen atoms.When identifying haloalkanes:

• Look for the presence of halogen atoms like \(-\text{F}\), \(-\text{Cl}\), \(-\text{Br}\), or \(-\text{I}\) in a molecule. This replacement gives haloalkanes distinct properties different from the parent alkanes.
• They often have higher boiling points than the alkanes they originate from, due to the increased weight and stronger intermolecular forces of attraction.
• Haloalkanes can be useful in many applications, including refrigerants, solvents, and as intermediates in the synthesis of other chemicals.

For example, \(\text{CH}_3\text{CH}_2\text{F}\) is a simple form of a haloalkane, known specifically as fluoroethane. The \(-\text{F}\) group here makes a significant impact on this compound's reactivity and physical properties.

Amine

Amines are a class of organic compounds derived from ammonia. They are characterized by the presence of an amino group, \(-\text{NH}_2\), replacing hydrogen atoms in the molecules.Understanding amines involves:

• The amino group grants amines similar properties to ammonia, including a typically fishy smell and the ability to form hydrogen bonds.
• This group can make molecules act as bases, accepting protons in solutions and participating in a variety of chemical reactions.
• Amines play crucial roles in both chemicals and biological systems; they are components of amino acids which are building blocks of proteins.

A familiar example of an amine is \(\text{CH}_3\text{CH}_2\text{NH}_2\), better known as ethylamine. The \(-\text{NH}_2\) functional group not only determines its classification as an amine but also gives it key properties such as basicity and reactivity.