Question

Name the following structures: (a) \(\mathrm{CH}_{3}-\mathrm{NH}-\mathrm{C}_{2} \mathrm{H}_{5} ;\) (b) \(\mathrm{C}_{6} \mathrm{H}_{5}-\mathrm{NH}-\mathrm{C}_{2} \mathrm{H}_{5}\) (c) \(\mathrm{NH}_{2}-\left(\mathrm{CH}_{2}\right)_{3}-\mathrm{NH}_{2}\) (d) \(\left(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}\right)_{3} \mathrm{~N}\) (e) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}-\mathrm{NH}_{2} ;\) (f) \(\mathrm{NH}_{2}-\mathrm{CH}_{2}-\mathrm{COOH}\) (g) \(\left(\mathrm{C}_{6} \mathrm{H}_{5}\right)_{2} \mathrm{NCH}_{3}\); (h) \(\mathrm{C}_{2} \mathrm{H}_{5}-\mathrm{NH}-\mathrm{CH}_{2} \mathrm{C}_{6} \mathrm{H}_{5}\)

Short answer

The short names for the given molecular structures are: (a) N-methylethanamine (b) N-phenylethanamine (c) 1,3-propanediamine (d) N,N,N-tripropylamine (e) 2-methylpropan-1-amine (f) 2-aminoethanoic acid (glycine) (g) N,N-diphenylmethanamine (h) N-phenylethanamine

Step-by-step solution

(a) CH3-NH-C2H5

This structure represents N-methylethanamine. The base structure is ethanamine (C2H5NH2), where a hydrogen atom of the amine group (-NH2) is replaced by a methyl group (CH3). Therefore, we write it as N-methylethanamine.

(b) C6H5-NH-C2H5

This structure represents N-phenylethanamine. The base structure is ethanamine (C2H5NH2) with one hydrogen (attached to Nitrogen) replaced by a phenyl group (C6H5). We follow a similar naming pattern as before - N-phenylethanamine.

(c) NH2-(CH2)3-NH2

This molecule is a diamine, as it has two amine groups (-NH2) in its structure. The chain contains 3 methylene groups (CH2), so the base structure is propane (C3H8). Because two hydrogens are replaced by amine groups, the name is following IUPAC nomenclature, 1,3-propanediamine.

(d) (CH3-CH2-CH2)3N

This molecule is a tertiary amine with a nitrogen atom bonded to three propyl groups (CH3CH2CH2). The name is following IUPAC nomenclature, N,N,N-tripropylamine.

(e) (CH3)2CH-NH2

This structure represents 2-methylpropan-1-amine. The base structure is propane (C3H8), where one hydrogen is replaced with an amine group, creating the base propylamine (C3H7NH2). The second carbon from the amine functional group also has a methyl group on it, so we name the compound: 2-methylpropan-1-amine.

(f) NH2-CH2-COOH

This molecule has an amine group (-NH2) and a carboxylic acid group (-COOH) connected by a methylene group (CH2). It is an α-amino acid, and in IUPAC nomenclature, it is referred to as 2-aminoethanoic acid. However, common nomenclature calls this molecule glycine.

(g) (C6H5)2NCH3

This structure represents N, N-diphenylmethanamine. The base structure is methanamine (CH3NH2), where both hydrogens attached to the nitrogen atom are replaced by two phenyl groups (C6H5). Using IUPAC nomenclature, we name the molecule N, N-diphenylmethanamine.

(h) C2H5-NH-CH2C6H5

This structure represents N-phenylethanamine in reverse form. The base compound is ethanamine (C2H5NH2) where a hydrogen atom of the amine group (-NH2) is replaced by a phenyl group (C6H5). Therefore, we write it as N-phenylethanamine.

Key concepts

Amines

Amines are a class of organic compounds that contain a basic nitrogen atom with a lone pair of electrons. They are derived from ammonia (NH₃) by replacing one or more hydrogen atoms with alkyl or aryl groups. This variation results in different types of amines:

• Primary amines (RNH₂): Contain one alkyl or aryl group attached to the nitrogen.
• Secondary amines (R₂NH): Have two alkyl or aryl groups attached.
• Tertiary amines (R₃N): Comprise three such groups attached to the nitrogen atom.

Amines are significant in both industrial and biological contexts, playing crucial roles in the manufacture of dyes, pharmaceuticals, and as building blocks for amino acids and proteins. In chemical structures, the presence of the amine group greatly influences the molecule's reactivity and interactions with other compounds.

Naming Organic Compounds

The IUPAC nomenclature provides a systematic way to name organic compounds based on their structures, ensuring clarity and consistency. This involves identifying the longest carbon chain, functional groups, and their positions on the chain. For naming amines:

• The longest alkyl chain attached to the nitrogen is selected as the parent name.
• When there are simple amine groups, they can be named by replacing the "-e" in the alkane name with "amine," such as "propane" becomes "propanamine."
• For substituents on nitrogen, use the prefix "N-" followed by the substituent name, like "N-methyl" for a methyl group on nitrogen.

With more complex molecules, detailed prefixes and suffixes can be used to convey the complete structure, aiding in the accurate depiction of molecular architecture.

Functional Groups

Functional groups are specific groupings of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. In organic chemistry, identifying these groups helps predict the behavior of compounds. Common functional groups include:

• Alcohols (-OH): Characterized by hydroxyl groups.
• Amines (-NH₂, -RNH, -NR₂): Contain nitrogen atoms bonded to carbon chains or rings.
• Carboxylic acids (-COOH): Known for having both a carbonyl and hydroxyl group attached to the same carbon.

Recognition of these groups is crucial, as they largely determine the properties and reactivity of organic compounds. For example, the presence of an amine group in an organic compound significantly alters its solubility, basicity, and engages in hydrogen bonding.

Organic Chemistry Education

Learning organic chemistry can initially be challenging due to the breadth of content and the complexity of molecular structures. However, grasping key principles like understanding functional groups and mastering IUPAC naming conventions is vital. Interactive tools and practical exercises, such as drawing structures or naming compounds, help reinforce learning.

• Breaking down complex concepts into smaller, manageable parts can aid understanding.
• Utilizing molecular models allows for a tangible understanding of three-dimensional structures.
• Regular practice with compound analysis and reaction mechanisms strengthens analytical skills.

Educational platforms often provide these interactive opportunities, offering simulations and exercises that align closely with theoretical teachings. By consistently applying these learning strategies, students can effectively navigate the vast landscape of organic chemistry.