Question

Draw a structural formula for each of the following compounds. a. 2,2 -dimethylheptane b. 2,3 -dimethylheptane c. 3,3-dimethylheptane d. 2,4 -dimethylheptane

Short answer

The structural formulas for the dimethylheptane isomers are as follows: a. 2,2-dimethylheptane: CH3-CH(CH3)2-CH2-CH2-CH2-CH2-CH3 b. 2,3-dimethylheptane: CH3-CH(CH3)-CH(CH3)-CH2-CH2-CH2-CH3 c. 3,3-dimethylheptane: CH3-CH2-CH(CH3)2-CH2-CH2-CH2-CH3 d. 2,4-dimethylheptane: CH3-CH(CH3)-CH2-CH(CH3)-CH2-CH2-CH3

Step-by-step solution

Analyze the IUPAC name

First, we break down each IUPAC name to understand the different components: a. 2,2-dimethylheptane: The base name of the compound is heptane, which means it has a 7-carbon main chain. The prefix "di-" in "dimethyl" indicates two methyl groups (-CH3) are attached to the main chain. The numbers 2,2 indicate that both methyl groups are attached to the 2nd carbon atom. b. 2,3-dimethylheptane: Similar to a, the base name is heptane. The two methyl groups are attached at the 2nd and 3rd carbon atoms. c. 3,3-dimethylheptane: The base name is heptane. The two methyl groups are attached to the 3rd carbon atom. d. 2,4-dimethylheptane: The base name is heptane. The two methyl groups are attached at the 2nd and 4th carbon atoms.

Draw the structural formula for each compound

a. 2,2-dimethylheptane: Draw a 7-carbon chain (heptane). Attach two methyl groups (-CH3) to the 2nd carbon atom. CH3-CH(CH3)2-CH2-CH2-CH2-CH2-CH3 b. 2,3-dimethylheptane: Draw a 7-carbon chain. Attach one methyl group to the 2nd carbon atom and another one to the 3rd carbon atom. CH3-CH(CH3)-CH(CH3)-CH2-CH2-CH2-CH3 c. 3,3-dimethylheptane: Draw a 7-carbon chain. Attach two methyl groups to the 3rd carbon atom. CH3-CH2-CH(CH3)2-CH2-CH2-CH2-CH3 d. 2,4-dimethylheptane: Draw a 7-carbon chain. Attach one methyl group to the 2nd carbon atom and another one to the 4th carbon atom. CH3-CH(CH3)-CH2-CH(CH3)-CH2-CH2-CH3 Now we have the structural formulas for each of the given dimethylheptane isomers.

Key concepts

IUPAC Nomenclature

The International Union of Pure and Applied Chemistry (IUPAC) nomenclature system is a standardized way of naming chemical compounds so scientists across the world can understand the exact structure being referred to. For organic molecules like alkanes, the IUPAC name provides important clues about the structure of the compound.

To break down an IUPAC name such as 2,2-dimethylheptane, we identify the following components:

• The root name: "heptane" indicates a chain with 7 carbon atoms.
• The prefix "di-" symbolizes that there are two identical groups attached to the main chain.
• Methyl "-CH₃" groups are commonly seen in organic compounds, indicating a one-carbon group attached to a carbon chain.
• Finally, the numbers (like 2,2) tell us the position on the main chain where these groups are attached.

This systematic approach allows for clear and unequivocal communication about complex molecules.

Structural Formulas

A structural formula is a drawing that shows not just the number of atoms, but how they are arranged and connected in an organic molecule. Unlike the simpler molecular formula, which only provides a count of atoms for each element, a structural formula conveys more details about how the atoms are bonded.

For example, the structural formula of 2,2-dimethylheptane doesn't just indicate seven carbons in the chain, with additional carbons as methyl groups at specific positions. Instead, it visually maps out the backbone of carbon atoms and all branches. The visual representation helps us see how the molecule is built, often revealing potential chemical properties or reactivity of the molecule.

Practicing how to draw these formulas refines our ability to understand and predict the behavior of organic chemicals, laying a foundation for further studies in organic reactions and synthesis.

Isomerism

Isomers are compounds that have the same molecular formula but different structural arrangements. In organic chemistry, isomerism plays a crucial role, especially when we consider compounds like alkanes. Each arrangement can give rise to different physical and chemical properties.

Dimethylheptane isomers, such as 2,2-dimethylheptane, 2,3-dimethylheptane, 3,3-dimethylheptane, and 2,4-dimethylheptane all share the same number of each type of atom, but what makes them distinct from each other is how these atoms are connected. The diverse possible arrangements of atoms create a unique structure for each isomer.

This concept of isomerism helps explain why substances with the same molecular formula can behave so differently. Understanding these differences is crucial for applications ranging from medicine to industrial chemistry.

Alkanes

Alkanes are a straightforward group of hydrocarbons made of carbon and hydrogen, exhibiting single C-C bonds. Their general formula is CₙH₂ₙ₊₂, where "n" represents the number of carbon atoms. Known for their saturated bond structure, alkanes are stable and less reactive than many other types of hydrocarbons.

The term "saturated" indicates that each carbon atom is bonded to four other atoms by single bonds. These molecules can differ in chain length or branching, leading to different isomeric forms such as those seen in dimethylheptanes.

Because of their simple structure and consistent properties, alkanes serve as an excellent introduction to organic chemistry. Their systematic nomenclature and the predictable linear or branched configurations allow students to apply principles like IUPAC naming, drawing of structural formulas, and exploring isomerism with clarity. Understanding their basic framework provides a foundation to tackle more complex organic compounds in the future.