Question

Draw all the structural isomers for amines having the molecular formula \(\mathrm{C}_{3} \mathrm{H}_{9} \mathrm{~N}\).

Short answer

There are four structural isomers: \(\mathrm{n{-}propylamine}\), \(\mathrm{isopropylamine}\), \(\mathrm{ethylmethylamine}\), \(\mathrm{trimethylamine}\).

Step-by-step solution

Understand the molecular formula

The molecular formula given is \(\mathrm{C}_{3} \mathrm{H}_{9} \mathrm{~N}\). This indicates there are three carbon atoms, nine hydrogen atoms, and one nitrogen atom in each molecule. Amines are organic compounds derived from ammonia and characterized by the presence of a nitrogen atom bonded to alkyl groups.

Identify potential backbones

For three carbon atoms, there are two potential chain backbones: a straight chain (\(\mathrm{n{-}propyl}\)) and a branched chain (\(\mathrm{isopropyl}\)). These will serve as the basic structures upon which the nitrogen atom can be attached.

Attach nitrogen to linear chain

For a straight chain (\(\mathrm{n{-}propyl}\)), the nitrogen atom can be attached to any of the three carbon atoms, leading to two primary isomers due to symmetry:1. \(\mathrm{n{-}propylamine}\) (\(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{NH}_{2}\)) - The nitrogen is bonded to an end carbon.2. \(\mathrm{isopropylamine}\) (\(\mathrm{(CH_{3})_{2}CHNH_{2}}\)) - The nitrogen is bonded to the middle carbon.

Consider secondary and tertiary structure isomers

For the \(\mathrm{n{-}propyl}\) backbone, examine the possibility of a cyclic or branched nitrogen. A secondary amine has two alkyl groups attached to the nitrogen atom, while a tertiary amine has three:1. \(\mathrm{ethylmethylamine}\) (\(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NHCH}_{3}\)) - Two different alkyl groups (ethyl, methyl) bonded to nitrogen.2. \(\mathrm{trimethylamine}\) (\(\mathrm{(CH_{3})_{3}N}\)) - A tertiary amine with three methyl groups attached to the nitrogen.

Key concepts

Amines

Amines are a fascinating group of organic compounds derived from ammonia. They are characterized by the presence of a nitrogen atom bonded to one or more alkyl groups. These compounds are classified based on the number of carbon-containing groups attached to the nitrogen:

• Primary Amines: One alkyl group attached.
• Secondary Amines: Two alkyl groups attached.
• Tertiary Amines: Three alkyl groups attached.

Amines play critical roles in various fields, particularly in pharmaceuticals and dye manufacturing. Their unique ability to form hydrogen bonds makes them reactive and versatile in chemical reactions.

Molecular Formula

The molecular formula of a compound gives a snapshot of its composition by indicating the number of each type of atom present in a molecule. For example, the formula \( \mathrm{C}_{3} \mathrm{H}_{9} \mathrm{~N} \) tells us that there are three carbon atoms, nine hydrogen atoms, and one nitrogen atom. This information is crucial in determining the possible structures or isomers a compound might have.

• Interpreting the Formula: Helps predict properties and reactivity.
• Structure Determination: Leads to identification of potential isomers.

Understanding molecular formulas is essential for organizing and predicting the behavior of molecules in chemical reactions.

Organic Chemistry

Organic chemistry is the study of carbon-containing compounds and their transformations. It is a vast field that underpins many industries, including pharmaceuticals, petrochemicals, and food. Within organic chemistry, understanding how molecules are structured and how they behave is the foundation of designing new materials or drugs.

Structural isomerism, a typical concept in organic chemistry, involves compounds with the same molecular formula but different arrangements of atoms. This leads to different properties and reactivity. Recognizing and drawing isomers is a core skill for anyone studying organic chemistry.

Propylamine

Propylamine, also known as n-propylamine, is an example of a primary amine. It consists of a three-carbon alkyl chain with the molecular formula \( \mathrm{C}_{3} \mathrm{H}_{9} \mathrm{~N} \), and the nitrogen atom is bonded to an end carbon.

• Structure: \( \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{NH}_{2} \)
• Properties: Colorless liquid with an ammonia-like odor.
• Uses: Found in the manufacture of pharmaceuticals and agricultural chemicals.

Recognizing how the placement of nitrogen affects the compound's properties is vital in applications requiring specific amine behaviors.

Nitrogen Atom

The nitrogen atom is a fundamental element in organic chemistry, particularly when it forms part of functional groups like amines. Nitrogen typically forms three covalent bonds, allowing it to participate in a variety of chemical structures.

• Bonding Versatility: Can form single, double, and even triple bonds.
• In Amines: Determines classification as primary, secondary, or tertiary.
• Reactivity: Nitrogen's lone pair of electrons makes it a nucleophile, fundamental to many organic reactions.

Understanding nitrogen's role and behavior helps predict how amine compounds will react under different chemical conditions.