Question

(a) There are two isomers with the formula \(\mathrm{C}_{4} \mathrm{H}_{10}\). Draw both the condensed and line structure for each isomer. (b) Using the structures you drew in (a) as a starting point, draw both the condensed and line structures for the four isomeric chlorides having the chemical formula \(\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Cl}\)

Short answer

There are two isomers for \(\mathrm{C}_{4}\mathrm{H}_{10}\) and four isomers for \(\mathrm{C}_{4}\mathrm{H}_{9}\mathrm{Cl}\), each with unique structures based on carbon atom arrangements.

Step-by-step solution

Identify Isomers for C4H10

The molecular formula \(\mathrm{C}_4\mathrm{H}_{10}\) corresponds to butane, which has two structural isomers: n-butane and isobutane (also known as 2-methylpropane). These isomers differ in the arrangement of their carbon atoms.

Draw Condensed Structures for C4H10 Isomers

For n-butane, the condensed structure is \(\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3\). Isobutane's condensed structure is \(\mathrm{(CH}_3\mathrm{)_3CH}\).

Draw Line Structures for C4H10 Isomers

In line structure notation, n-butane is drawn as a straight line of four carbon atoms: \(\displaystyle \text{—} \text{—} \text{—} \text{—}\). Isobutane is depicted with a branching at the first carbon: \(\displaystyle \text{—} \underset{\text{—}}{\vert} \text{—} \).

Derive Isomeric Chlorides for C4H9Cl

For n-butane, replace one hydrogen atom with a chlorine atom at each unique carbon position, resulting in: 1-chlorobutane (\(\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{Cl}\)) and 2-chlorobutane (\(\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH(Cl)CH}_3\)). For isobutane, replace a hydrogen with chlorine, yielding: 1-chloro-2-methylpropane (\(\mathrm{(CH}_3\mathrm{)_2CHCH}_2\mathrm{Cl}\)) and 2-chloro-2-methylpropane (\(\mathrm{(CH}_3\mathrm{)_3CCl}\)).

Draw Condensed Structures for C4H9Cl Isomers

Condensed structures for the chlorides are as follows: 1-chlorobutane: \(\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{Cl}\); 2-chlorobutane: \(\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH(Cl)CH}_3\); 1-chloro-2-methylpropane: \(\mathrm{(CH}_3\mathrm{)_2CHCH}_2\mathrm{Cl}\); 2-chloro-2-methylpropane: \(\mathrm{(CH}_3\mathrm{)_3CCl}\).

Draw Line Structures for C4H9Cl Isomers

Line structure representations are: 1-chlorobutane: \(\text{—} \text{—} \text{—} \text{—} \text{Cl}\); 2-chlorobutane: \(\text{—} \text{—} \text{—Cl} \text{—}\); 1-chloro-2-methylpropane: \(\text{—} \underset{\text{| Cl}}{\underset{\text{—}}{\vert}} \text{—}\); and 2-chloro-2-methylpropane: \(\text{—} \underset{\text{| Cl}}{\underset{\text{|}}{\vert}} \).

Key concepts

Structural Isomers

In organic chemistry, structural isomers are compounds that have the same molecular formula but different arrangements of atoms. This means that although the number of each kind of atom is the same, the connectivity is different. As a consequence, structural isomers can have varying physical and chemical properties.

• For example, n-butane and isobutane both have the molecular formula \(\mathrm{C}_4\mathrm{H}_{10}\).
• Their difference lies in the connectivity of the carbon atoms. N-butane is a straight-chain hydrocarbon, while isobutane is branched.

Understanding structural isomers is crucial in organic chemistry because it helps us see how slight changes in the molecular structure can drastically alter a compound's behavior.

Butane

Butane, a hydrocarbon, is a member of the alkane family characterized by single bonds between carbon atoms. It has the molecular formula \(\mathrm{C}_4\mathrm{H}_{10}\). Butane has two primary forms: n-butane and isobutane.

• N-butane, also known as "normal" butane, is a linear molecule with a continuous chain of four carbon atoms: \(\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3\).
• In contrast, isobutane has a branched structure with the formula \(\mathrm{(CH}_3\mathrm{)_3CH}\), where three methyl groups are attached to a central carbon atom.

Butane is commonly used as a fuel in lighters and portable stoves. The structural difference between its isomers leads to distinct boiling points and other properties. This serves as a valuable example of how molecular structure affects physical properties.

Chemical Structures

In organic chemistry, chemical structures depict the arrangement of atoms within molecules. These structures can be represented in several ways: condensed structures and line (or skeletal) structures are the most common.

• Condensed structures display groups of atoms such as \(\mathrm{CH}_3\) or \(\mathrm{CH}_2\) together, offering a detailed view of the molecular makeup.
• Line structures, on the other hand, simplify the depiction by using lines to represent carbon-carbon bonds, where carbon atoms are at the ends and vertices of lines by default.

Both methods have their purpose. Condensed structures provide clarity, especially for smaller molecules. Line structures offer simplicity for larger organic molecules, making it easier to understand the overall skeleton of the molecule.

Chloroalkanes

Chloroalkanes are a type of chlorinated hydrocarbon where one or more hydrogen atoms in an alkane are replaced by chlorine atoms. These are important in both industrial applications and laboratory settings.

• The chemical formula \(\mathrm{C}_4\mathrm{H}_9\mathrm{Cl}\) indicates that these molecules are derived from butane with one hydrogen swapped for chlorine.
• The replacement can occur at different positions, leading to the formation of isomers. For instance, 1-chlorobutane and 2-chlorobutane derive from n-butane, while 1-chloro-2-methylpropane and 2-chloro-2-methylpropane derive from isobutane.

Chloroalkanes serve as intermediates in the synthesis of various compounds and have applications in the production of pharmaceuticals and refrigerants. Different isomers may have different properties, which highlights the importance of understanding their structural nuances in chemical processes.