Question

Just as ammonia, \(\mathrm{NH}_3\), is a weak Lewis base, there is a largé group of nitrogen-containing organic compounds that behaves like weak bases and is known as: A. amides B. amines C. ethanol alcohols D. ethers

Short answer

B. Amines

Step-by-step solution

- Understanding the Question

First, recognize that ammonia \( \mathrm{NH}_3 \) is a weak Lewis base. The question is asking for a class of nitrogen-containing organic compounds that also act as weak bases.

- Define Each Option

Next, realize what each of the given options represents:A. Amides: Compounds with the functional group \(\mathrm{-CONH_2}\).B. Amines: Compounds with the functional group \(\mathrm{-NH_2}\) or derivatives.C. Ethanol Alcohols: Organic compounds with \(\mathrm{-OH}\) attached to an ethane chain.D. Ethers: Compounds with an \(\mathrm{-O-}\) linking two alkyl groups.

- Identify the Best Match

Amides \(\mathrm{-CONH_2}\) and Amines \(\mathrm{-NH_2}\) both contain nitrogen, but amides are not categorized as weak bases. Ethanol alcohols and ethers do not contain nitrogen or act as bases. Thus, Amines, which contain \(\mathrm{-NH_2}\) groups, act as weak bases similar to ammonia.

- Conclusion

Based on the analysis, Amines are the nitrogen-containing organic compounds that behave like weak Lewis bases.

Key concepts

Amines

Amines are organic compounds that contain nitrogen atoms bonded to hydrogen or alkyl groups, typically with the general form \(\text{-NH}_2\). Amines are structurally similar to ammonia \(\text{NH}_3\) with one or more of the hydrogen atoms substituted by other groups. This substitution makes them versatile and important in both biological systems and synthetic chemistry.
Amines can be classified into three types based on the number of alkyl or aryl groups attached to the nitrogen atom. Primary amines have one alkyl/aryl group (R-NH2), secondary amines have two (R2-NH), and tertiary amines have three (R3-N).
The lone pair of electrons on the nitrogen atom allows amines to act as Lewis bases. This means they can donate a pair of electrons to accept protons (hydrogen ions), or bond with other electron-deficient species. This behavior is similar to ammonia, making amines essential in various chemical reactions such as nucleophilic substitutions or as intermediates in the synthesis of other compounds.
Amines are also found extensively in biological systems, such as amino acids and neurotransmitters, playing vital roles in cellular functions and signaling processes.

Lewis Bases

Lewis bases are compounds that can donate an electron pair to form a covalent bond. Named after Gilbert N. Lewis, this concept broadens the definition of acids and bases beyond traditional hydrogen ion transfers.
According to Lewis theory, a Lewis base must have a lone pair of electrons available to donate. For example, ammonia \(\text{NH}_3\) is a classic Lewis base due to its lone pair on the nitrogen atom. Similarly, amines are also Lewis bases because the nitrogen in amines possesses a lone pair of electrons that can partake in bonding.
When a Lewis base donates its lone pair of electrons, it forms a coordinate covalent bond with a Lewis acid, which is an electron pair acceptor. This interaction is crucial in many chemical reactions, including catalysis and coordination chemistry.
Understanding Lewis bases is essential for grasping many organic reactions, particularly those involving nucleophiles (Lewis bases) attacking electrophiles (Lewis acids). This also helps in explaining the behavior of compounds such as amines in organic synthesis and biological systems.

Functional Groups

Functional groups are specific groups of atoms within molecules that determine the characteristics and chemical reactivity of those molecules. These groups are key to organizing organic chemistry into manageable sections,
For example, the functional group in amines is the amino group (NH2) which defines their properties such as basicity and solubility. Another crucial functional group is the hydroxyl group \(\text{-OH}\) found in alcohols, which imparts properties like hydrogen bonding and solubility in water.
Functional groups classify organic compounds and predict their reactions. For instance:

• Carboxyl groups (COOH) in carboxylic acids make them acidic and reactive towards bases and alcohols.
• Carbonyl groups (C=O), found in aldehydes and ketones, are highly reactive and form the basis of various addition and condensation reactions.
• Ethers (C-O-C) show unique solvency properties compared to other organic compounds.

Recognizing functional groups helps chemists synthesize new compounds and understand the mechanisms of chemical reactions. For students, mastering functional groups is a crucial step toward excelling in organic chemistry.