Question

Draw structural formulas for the three tertiary \(\left(3^{\circ}\right)\) amines with the molecular formula \(\mathrm{C}_{5} \mathrm{H}_{13} \mathrm{~N}\).

Short answer

Question: Draw three tertiary amines with the molecular formula C5H13N and provide their structural formulas. Answer: The structural formulas for the three tertiary amines with the molecular formula C5H13N are as follows: 1. N(CH3)(C4H9) 2. N(CH3)2(C3H7) 3. N(C2H5)3

Step-by-step solution

Identify the carbon skeletons

To create a tertiary amine with 5 carbons and 1 nitrogen, we can have three possible carbon skeletons that can be formed by adding the nitrogen in different positions: 1. Four carbons in a continuous chain with one carbon branch: C4H9 (Example: butyl group) 2. Three carbons in a continuous chain with two carbon branches: C3H7 (Example: propyl group) 3. Two carbons in a continuous chain with three carbon branches: C2H5 (Example: ethyl group)

Draw the structural formulas for each carbon skeleton

For each of the carbon skeletons we identified, we will draw a structural formula containing a nitrogen atom bonded to three different carbon groups. 1. Four carbons in a continuous chain with one carbon branch: C4H9 The tertiary amine will have a nitrogen bonded to one methyl group (CH3) and a butyl group (C4H9). It can be represented as: N(CH3)(C4H9) 2. Three carbons in a continuous chain with two carbon branches: C3H7 The tertiary amine will have a nitrogen bonded to two methyl groups (CH3) and a propyl group (C3H7). It can be represented as: N(CH3)2(C3H7) 3. Two carbons in a continuous chain with three carbon branches: C2H5 The tertiary amine will have a nitrogen bonded to three ethyl groups (C2H5). It can be represented as: N(C2H5)3

Final structural formulas

We have now drawn the structural formulas for the three tertiary amines with the molecular formula C5H13N: 1. N(CH3)(C4H9) 2. N(CH3)2(C3H7) 3. N(C2H5)3

Key concepts

Understanding Structural Formulas

When studying about tertiary amines—or any organic compound—it's important to be able to visualize and understand their structural formulas. These depict the molecule's architecture, showing how atoms are connected. In organic chemistry, structural formulas are invaluable because they convey information about the molecule's geometry that molecular formulas cannot.

Let's take the exercise as an example. The structural formulas for the tertiary amines were drawn from their identified carbon skeletons. Carbon skeletons are the backbone or framework of a molecule, representing the chain or ring of carbon atoms. By adding substituents like a nitrogen atom and its connected hydrogen atoms or even other carbons, the full structure of the amine is realized.

When a structural formula is built, each line represents a bond between the atoms, and the elemental symbols (C for carbon, N for nitrogen, etc.) are used to depict the identity of the atoms. These visual representations help illustrate the three-dimensionality of molecules and the way in which the atoms are bonded, facilitating a better understanding of their chemical behavior.

Deciphering Carbon Skeletons in Molecules

The concept of a carbon skeleton is critical to understanding organic molecules. It's the chain or ring that consists solely of carbon atoms to which other atoms or groups of atoms are attached. For the tertiary amines in our exercise, different carbon skeletons lead to different structures, despite having the same molecular formula \(\mathrm{C}_{5} \mathrm{H}_{13} \mathrm{N}\).

When attempting to draw the structural formulas, the first step was identifying potential carbon skeletons. Notice how different the skeletons can be: a long chain with a single branch, a shorter chain with more branching, or a chain with multiple branches. It's like building different models from the same set of building blocks—each arrangement gives the molecule unique properties.

Understanding this concept allows students to see beyond just the formula and grasp the diversity that carbon's bonding versatility brings to organic structures. This is crucial for predicting physical and chemical properties which are intimately related to how the carbon atoms are laid out in a molecule.

Interpreting Molecular Formulas

The molecular formula is like the simplest summary of a compound's composition. Take the molecular formula \(\mathrm{C}_{5} \mathrm{H}_{13} \mathrm{N}\) from our exercise. This formula tells you that the molecule comprises five carbon atoms, thirteen hydrogen atoms, and one nitrogen atom. While it doesn't show the structure or layout of those atoms—that's what structural formulas are for—it does provide a quick overview of what is in a molecule.

However, one must be cautious; different structures might have the same molecular formula, a concept known as isomerism. In the case of the tertiary amines we're studying, they all share the same molecular formula, yet as we've explored, their structural formulas vary significantly. This is why students must learn to interpret both molecular and structural formulas to gain a complete understanding of the nature of a compound.

Accurately interpreting molecular formulas in tandem with structural information is essential in organic chemistry, as it helps students predict and comprehend the chemical’s identity and helps in picturing the molecule in three dimensions, which is valuable for understanding their reactivity and interactions with other molecules.