Question

Draw structural formulas for (a) The four primary (1 \(\left.1^{\circ}\right)\) amines with the molecular formula \(\mathrm{C}_{4} \mathrm{H}_{11} \mathrm{~N}\). (b) The three secondary \(\left(2^{\circ}\right)\) amines with the molecular formula \(\mathrm{C}_{4} \mathrm{H}_{11} \mathrm{~N}\). (c) The one tertiary \(\left(3^{\circ}\right)\) amine with the molecular formula \(\mathrm{C}_{4} \mathrm{H}_{11} \mathrm{~N}\).

Short answer

Question: Draw structural formulas for primary, secondary, and tertiary amines with the molecular formula C4H11N and provide their names. Answer: Primary amines: 1) Butylamine: CH3CH2CH2CH2NH2 2) Isobutylamine: CH3CH2CH(CH3)NH2 3) sec-Butylamine: CH3C(CH3)CH2NH2 4) tert-Butylamine: C(CH3)3NH2 Secondary amines: 1) N-Methylpropylamine: CH3CH2CH2NHCH3 2) N-Methylisopropylamine: CH3CH2NHC(CH3)2 3) N,N-Dimethylamine: CH3N(C(CH3)3 Tertiary amine: 1) N,N-Diethylmethylamine: CH3N(CH2CH3)2

Step-by-step solution

Primary amines

For primary (1°) amines, there is only one alkyl group attached to the nitrogen atom, and three hydrogens. We need to draw the four isomers that fulfill this condition. All four structures have the molecular formula C4H11N. 1) \(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{NH}_{2}\) - Butylamine 2) \(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}(\mathrm{CH}_{3})\mathrm{NH}_{2}\) - Isobutylamine 3) \(\mathrm{CH}_{3}\mathrm{C}(\mathrm{CH}_{3})\mathrm{CH}_{2}\mathrm{NH}_{2}\) - sec-Butylamine 4) \(\mathrm{C}(\mathrm{CH}_{3})_{3}\mathrm{NH}_{2}\) - tert-Butylamine

Secondary amines

For secondary (2°) amines, there are two alkyl groups attached to the nitrogen atom, and two hydrogens. We need to draw the three isomers that fulfill this condition. All three structures have the molecular formula C4H11N. 1) \(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{NH}\mathrm{CH}_{3}\) - N-Methylpropylamine 2) \(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}\mathrm{C}(\mathrm{CH}_{3})_{2}\) - N-Methylisopropylamine 3) \(\mathrm{CH}_{3}\mathrm{NH}\mathrm{C}(\mathrm{CH}_{3})_{3}\) - N,N-Dimethylamine

Tertiary amine

For tertiary (3°) amine, there are three alkyl groups attached to the nitrogen atom, and one hydrogen. We need to draw the only isomer that fulfills this condition. This structure has the molecular formula C4H11N. 1) \(\mathrm{CH}_{3}\mathrm{N}(\mathrm{CH}_{2}\mathrm{CH}_{3})_{2}\) - N,N-Diethylmethylamine

Key concepts

Structural Formulas

Structural formulas are diagrams that show how atoms in a molecule are connected. They provide insight into the molecule's shape and the spatial arrangement of atoms.
Each line in these diagrams represents a bond between atoms. To understand how structural formulas work, let's take a closer look at amines.
Amines are molecules derived from ammonia \(\mathrm{NH}_3\) where one or more hydrogen atoms are replaced by alkyl or aryl groups.
In structural formulas,

• Nitrogen is usually represented by the letter 'N.'
• Hydrogen atoms linked to nitrogen may not be shown in older, less detailed structures, which is why you see some nitrogen atoms without visible hydrogen in more simplified formats.

Isomers

Isomers are compounds with the same molecular formula but different structural arrangements. They might have different physical and chemical properties.
For instance, the molecular formula \(\mathrm{C}_{4}\mathrm{H}_{11}\mathrm{N}\) can form different isomers by arranging the carbon and nitrogen atoms differently around each other.
In our discussion on amines, one can have primary, secondary, and tertiary arrangements which result in multiple isomers even though they have the same molecular formula.

• Structural isomers differ in the covalent arrangements of their atoms.
• Stereoisomers differ in the spatial orientation of atoms.

Primary Amines

Primary amines, denoted as 1°, contain one alkyl group attached to the nitrogen atom, leaving it with two hydrogen atoms.
For example, with \(\mathrm{C}_{4}\mathrm{H}_{11}\mathrm{N}\), you can have four isomers of primary amines:

• Butylamine: \((\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{NH}_{2})\).
• Isobutylamine: \((\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}(\mathrm{CH}_{3})\mathrm{NH}_{2})\).
• sec-Butylamine: \((\mathrm{CH}_{3}\mathrm{C}(\mathrm{CH}_{3})\mathrm{CH}_{2}\mathrm{NH}_{2})\).
• tert-Butylamine: \((\mathrm{C}(\mathrm{CH}_{3})_{3}\mathrm{NH}_{2})\).

These structural variations define their diverse chemical behaviors while maintaining the same basic nitrogen bonding.

Secondary Amines

Secondary amines (2°) feature two alkyl groups attached to the nitrogen atom while carrying only one hydrogen atom.
In the case of our given formula, \(\mathrm{C}_{4}\mathrm{H}_{11}\mathrm{N}\), there are three possible isomers:

• N-Methylpropylamine: \((\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{NH}\mathrm{CH}_{3})\).
• N-Methylisopropylamine: \((\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}\mathrm{C}(\mathrm{CH}_{3})_{2})\).
• N, N-Dimethylamine: \((\mathrm{CH}_{3}\mathrm{NH}\mathrm{C}(\mathrm{CH}_{3})_{3})\).

These distinct arrangements influence major properties like boiling points and solubility.

Tertiary Amines

Tertiary amines (3°) consist of three alkyl groups attached to the nitrogen atom, with no hydrogen atoms directly attached to the nitrogen.
Here, it's represented by just one isomer for the molecular formula \(\mathrm{C}_{4}\mathrm{H}_{11}\mathrm{N}\):

• N, N-Diethylmethylamine: \((\mathrm{CH}_{3}\mathrm{N}(\mathrm{CH}_{2}\mathrm{CH}_{3})_{2})\).

This structure is more sterically hindered compared to primary or secondary amines, which can impact its reactivity and interactions with other molecules.