Question

Convert the following molecular formulas into line-bond structures that are consistent with valence rules: (a) \(\mathrm{C}_{3} \mathrm{H}_{8}\) (b) \(\mathrm{CH}_{5} \mathrm{~N}\) (c) \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}\) (2 possibilities) (d) \(\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{Br}\) (2 possibilities) (e) \(\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}\) (3 possibilities) (f) \(\mathrm{C}_{3} \mathrm{H}_{9} \mathrm{~N}\) (4 possibilities)

Short answer

Finished drawing line-bond structures for all given molecular formulas as described in solution steps.

Step-by-step solution

Understand Valence Rules

Before converting molecular formulas to line-bond structures, understand that carbon typically forms four bonds, nitrogen forms three bonds, oxygen forms two bonds, hydrogen forms one bond, and halogens like bromine form one bond.

Convert C3H8 to Line-Bond Structure

For \(C_3H_8\), which is propane, connect three carbon atoms in a chain with each carbon forming single bonds to sufficient hydrogen atoms to satisfy the valence of four for carbon:\[- H_3C - CH_2 - CH_3 -\].Each carbon atom makes four single bonds while each hydrogen atom is bonded to carbon.

Convert CH5N to Line-Bond Structures

For \(CH_5N\), create structures starting with one nitrogen and one carbon, like \(NH_3\) (ammonia) bonded to a \(CH_2\) (methylene group) forming methyl amine:\[H_3C - NH_2\],where nitrogen forms three bonds with hydrogens and one with carbon.

Convert C2H6O to Line-Bond Structures

For \(C_2H_6O\), there are two possibilities:1. **Ethanol**: Connect two carbon atoms, then attach an -OH group to one:\[- CH_3 - CH_2 - OH -\].2. **Dimethyl ether**: Attach each carbon atom to an oxygen atom linked to each other:\[- CH_3 - O - CH_3 -\].

Convert C3H7Br to Line-Bond Structures

For \(C_3H_7Br\), we have two isomeric possibilities:1. **1-Bromopropane** where Br is attached to one terminal carbon:\[- CH_2Br - CH_2 - CH_3 -\].2. **2-Bromopropane** where Br is attached to the middle carbon:\[- CH_3 - CHBr - CH_3 -\].

Convert C2H4O to Line-Bond Structures

For \(C_2H_4O\), there are three isomeric possibilities:1. **Acetaldehyde** with a carbonyl (C=O) group: \[- CH_3 - CHO -\]. 2. **Ethylene oxide**, a cyclic ether: \[\text{Epoxide ring: } C_2H_4O \]. 3. **Vinyl alcohol** with an OH group bonded to a sp2 hybridized carbon:\[- CH_2 = CH - OH -\].

Convert C3H9N to Line-Bond Structures

For \(C_3H_9N\), there are four possible isomeric structures:1. **Propylamine**: \[- CH_3 - CH_2 - CH_2 - NH_2 -\].2. **Isopropylamine**: \[- CH_3 - CH(NH_2) - CH_3 -\].3. **Dimethylamine (as a secondary amine)**: \[- CH_3 - NH - CH_2 - CH_3 -\].4. **Trimethylamine (as a tertiary amine)**: \[- (CH_3)_3N \].

Key concepts

Molecular Formulas

Molecular formulas are a concise way to represent the number and type of atoms in a molecule. They provide the foundational information needed to understand the structure of a compound. For example,

• \(C_3H_8\) represents propane, indicating it consists of three carbon atoms and eight hydrogen atoms.
• \(CH_5N\) suggests a compound comprising one carbon, five hydrogens, and one nitrogen, such as methyl amine.

While they tell you what atoms are present, they don't show how these atoms are bonded together. That's where line-bond structures come into play. Understanding molecular formulas is the first step before diving deeper into the structural representation of organic compounds.

Line-bond Structures

Line-bond structures, often called Lewis structures, visually represent molecules showing how atoms are bonded. In these diagrams:

• Lines portray bonds between atoms — single, double, or triple, indicating the type of bond.
• If the carbon is involved, assume that each line extended from it is a C-H bond unless stated otherwise.

This is especially useful in organic chemistry, where the arrangement of atoms can vastly affect the properties and behavior of a molecule. For example,

• In propane \(C_3H_8\), the structure \(- H_3C - CH_2 - CH_3 -\) illustrates each carbon atom forming single bonds with enough hydrogen atoms to satisfy its four-bond requirement.

By converting molecular formulas to line-bond structures, chemists can predict molecular interactions and functions.

Isomers

Isomers are compounds with the same molecular formula but different arrangements of atoms. This diversity in structure leads to different physical and chemical properties. For example,

• \(C_2H_6O\) can represent both ethanol and dimethyl ether, each having distinct structures and uses.
• Similarly, \(C_3H_7Br\) can be either 1-bromopropane or 2-bromopropane.

Structural isomers vary because of different connectivity between atoms, and this influences how they interact in chemical reactions. Recognizing and converting molecular formulas to depict different isomers is a fundamental skill in organic chemistry that showcases the complexity and versatility of chemical compounds.

Organic Chemistry

Organic chemistry primarily studies carbon-containing compounds and their transformations. Living organisms are composed mainly of such compounds, making this branch of chemistry essential for understanding life at a molecular level. Central to organic chemistry is the concept of hydrocarbons, which are compounds made entirely of carbon and hydrogen atoms, like propane (\(C_3H_8\)). These hydrocarbons can form the basis for more complex structures by incorporating different functional groups.

• These include alcohols like ethanol in \(C_2H_6O\), where the -OH group is added to the hydrocarbon framework.
• Amines, another class of organic compounds, include things like methyl amine (\(CH_5N\)).

Understanding how carbon can form stable, complex structures is at the heart of organic chemistry.

Bonding in Molecules

Bonding in molecules determines the structure and properties of compounds. There are different types of bonds including single, double, and triple bonds, each defining a unique spatial and electronic arrangement. In organic molecules:

• Single bonds, like in propane (\(C_3H_8\)), provide flexibility within the molecule.
• Double bonds, present in structures such as vinyl alcohol (an isomer of \(C_2H_4O\)), create rigidity and influence reactivity.
• Triple bonds, though not shown in the current examples, arise in other types of organic molecules, like alkynes, introducing even more complexity.

Understanding these bonding scenarios and their implications on molecular geometry and function is vital for grasping the intricacies of molecular chemistry.