Question

Write molecular and structural formulas for these compounds. (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NHCH}_{2} \mathrm{CH}_{3}\) (b) \(\mathrm{CH}_{3} \mathrm{NH}_{2}\) (c) \(\mathrm{CH}_{3} \mathrm{CHClCH}_{3}\) (d) \(\mathrm{CH}_{2} \mathrm{OHCHOHCH}_{2} \mathrm{OH}\)

Short answer

(a) C₄H₁₁N, CH₃CH₂NHCH₂CH₃; (b) CH₅N, CH₃NH₂; (c) C₃H₇Cl, CH₃CHClCH₃; (d) C₃H₈O₃, CH₂OHCHOHCH₂OH.

Step-by-step solution

Identify Molecular Formula for Compound (a)

The compound is written as \( \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NHCH}_{2} \mathrm{CH}_{3} \). Count the total number of each type of atom. There are 4 carbon (C) atoms, 11 hydrogen (H) atoms, and 1 nitrogen (N) atom. So, the molecular formula is \( \mathrm{C}_{4} \mathrm{H}_{11} \mathrm{N} \).

Write Structural Formula for Compound (a)

The structure of \( \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NHCH}_{2} \mathrm{CH}_{3} \) represents a chain with an amino group. Draw the structure as: \( \mathrm{CH}_{3} - \mathrm{CH}_{2} - \mathrm{NH} - \mathrm{CH}_{2} - \mathrm{CH}_{3} \).

Identify Molecular Formula for Compound (b)

The molecular formula is straight from the symbols given: \( \mathrm{CH}_{3} \mathrm{NH}_{2} \). It consists of 1 carbon (C), 5 hydrogens (H), and 1 nitrogen (N), so the molecular formula is \( \mathrm{C}_{1} \mathrm{H}_{5} \mathrm{N} \) or simply \( \mathrm{CH}_{5} \mathrm{N} \).

Write Structural Formula for Compound (b)

\( \mathrm{CH}_{3} \mathrm{NH}_{2} \) represents a simple amine where the \( \mathrm{NH}_{2} \) group is attached to a methyl group. The structural formula can be drawn as \( \mathrm{CH}_{3} - \mathrm{NH}_{2} \).

Identify Molecular Formula for Compound (c)

The compound \( \mathrm{CH}_{3} \mathrm{CHClCH}_{3} \) contains 3 carbon (C) atoms, 7 hydrogen (H) atoms, and 1 chlorine (Cl) atom. Thus, the molecular formula is \( \mathrm{C}_{3} \mathrm{H}_{7} \mathrm{Cl} \).

Write Structural Formula for Compound (c)

The structure shows 1-chloropropane with chlorine attached to the second carbon. Draw the structural formula as \( \mathrm{CH}_{3} - \mathrm{CHCl} - \mathrm{CH}_{3} \).

Identify Molecular Formula for Compound (d)

The compound \( \mathrm{CH}_{2} \mathrm{OHCHOHCH}_{2} \mathrm{OH} \) represents propane-1,2,3-triol. There are 3 carbon (C), 8 hydrogen (H), and 3 oxygen (O) atoms. So, the molecular formula is \( \mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{3} \).

Write Structural Formula for Compound (d)

The compound is a triol with hydroxy groups attached to each carbon. The structural formula is \( \mathrm{CH}_{2}OH - \mathrm{CHOH} - \mathrm{CH}_{2}OH \).

Key concepts

Structural Formulas

Structural formulas are an essential way of representing molecules to depict how atoms in a molecule are arranged and bonded together. Unlike molecular formulas, which solely list the number and types of atoms present, structural formulas provide insight into a molecule's shape and connectivity. For example, in the compound \( \mathrm{CH}_{3} - \mathrm{CH}_{2} - \mathrm{NH} - \mathrm{CH}_{2} - \mathrm{CH}_{3} \), the structural formula shows the sequence of atoms and the presence of a nitrogen atom, highlighting its role as an amine. The structural formula answers questions about the molecule's geometry, which is critical in understanding the compound's reactivity and interactions with other molecules.

Structural formulas not only consist of lines and symbols but also employ spatial diagrams when stereochemistry (3D orientation) is significant. While teaching, emphasizing the structural aspects allows students to predict molecular behavior better. Hence, this clarity is vital for disciplines like organic chemistry, where the structure significantly influences the molecule’s properties and function.

Chemical Compounds

Chemical compounds consist of two or more elements chemically bonded together, resulting in new substances with unique properties. They can be classified broadly into two categories: ionic and covalent compounds.

In organic chemistry, which focuses on carbon-containing compounds, covalent bonding predominates. For instance, the compound \( \mathrm{CH}_{3}\mathrm{CHClCH}_{3} \) is an example of an organic compound that features covalent bonds between carbon, hydrogen, and chlorine atoms. This chemical compound, known as 1-chloropropane, elucidates the basic principles of organic chemistry, where atoms share electrons to form stable structures.

Understanding chemical compounds involves more than just knowing their molecular and structural formulas. It's crucial to comprehend how these constituent atoms interact during chemical reactions. This knowledge allows chemists to predict compound reactivity, mechanisms, and the resultant products accurately. Knowing how elements combine to form compounds helps to appreciate the wide diversity and functionality of substances around us.

Organic Chemistry

Organic chemistry is the study of carbon-containing compounds. It is a vast field that extends beyond simple hydrocarbons to include numerous derivatives, like alcohols, amines, and much more. Carbon's ability to form long chains and rings through covalent bonding makes it foundational in chemistry of life.

The examples provided, such as \( \mathrm{CH}_{3}\mathrm{NH}_{2} \) (methylamine) and \( \mathrm{CH}_{2} \mathrm{OH} ext{-}\mathrm{CHOH} ext{-}\mathrm{CH}_{2} \mathrm{OH} \) (propylene glycol), highlight the variability and complexity in organic chemistry. Methylamine, for instance, demonstrates nitrogen's incorporation into the carbon framework, forming an amine with distinct properties. Meanwhile, propylene glycol showcases a molecule with multiple hydroxyl (-OH) groups, classifying it as a triol.

Organic chemistry's importance lies in its application across pharmaceuticals, materials science, and biochemistry. Understanding the principles of structure, reactivity, and synthesis in this field unlocks pathways to creating new materials and medicines, illustrating the subject's crucial role in scientific advancements.