Question

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

Short answer

a. 2,2-dimethylhexane: \[CH3-CH(CH3)-CH(CH3)-CH2-CH2-CH3\] b. 2,3-dimethylhexane: \[CH3-CH(CH3)-CH(CH3)-CH2-CH2-CH3\] c. 3,3-dimethylhexane: \[CH3-CH2-CH(CH3)-CH(CH3)-CH2-CH3\] d. 3,4-dimethylhexane: \[CH3-CH2-CH(CH3)-CH(CH3)-CH2-CH3\] e. 2,4-dimethylhexane: \[CH3-CH(CH3)-CH2-CH(CH3)-CH2-CH3\]

Step-by-step solution

Identify the main carbon chain in each compound

All five compounds are dimethylhexanes, which means they are all derived from a hexane molecule and have two methyl (-CH3) groups. The base molecule, hexane, has six linearly connected carbon atoms: C-C-C-C-C-C

Locate the positions of the methyl groups

The numbers given in the compound names indicate the positions of the two methyl groups attached in the hexane carbon chain. For example, 2,2-dimethylhexane means that both methyl groups are at the second carbon atom.

Draw the structural formula for each compound

a. 2,2-dimethylhexane: \[ CH3-CH(CH3)-CH(CH3)-CH2-CH2-CH3 \] b. 2,3-dimethylhexane: \[ CH3-CH(CH3)-CH(CH3)-CH2-CH2-CH3 \] c. 3,3-dimethylhexane: \[ CH3-CH2-CH(CH3)-CH(CH3)-CH2-CH3 \] d. 3,4-dimethylhexane: \[ CH3-CH2-CH(CH3)-CH(CH3)-CH2-CH3 \] e. 2,4-dimethylhexane: \[ CH3-CH(CH3)-CH2-CH(CH3)-CH2-CH3 \] In conclusion, we have drawn the desired structural formulas for all the given dimethylhexane compounds using information about the positions of the methyl groups on the hexane carbon backbone.

Key concepts

Structural Formula

In organic chemistry, a structural formula is a way to represent a molecule. It shows how atoms are arranged and bonded together. Unlike a simple molecular formula, which only indicates the numbers of each type of atom, a structural formula adds clarity by illustrating connections between atoms. This helps in understanding the physical and chemical properties of the compound.

To draw a structural formula, start by identifying the main carbon backbone. Then, add all side groups and atoms accordingly. Use lines to represent bonds between atoms:

• A single line (−) stands for a single bond.
• A double line (=) stands for a double bond.
• A triple line (≡) stands for a triple bond.

By following these steps, students can draw accurate structural formulas for different organic molecules.

Dimethylhexane

Dimethylhexane is a type of alkane. Alkanes are hydrocarbons with single-bonded carbon and hydrogen atoms, making them saturated compounds. Dimethylhexane specifically, refers to a hexane chain with two methyl groups attached.

• "Di-" indicates two methyl groups (-CH₃).
• "Hexane" refers to the main chain containing six carbon atoms.

Different variations of dimethylhexane exist, depending on where the methyl groups are attached on the hexane chain. For instance, 2,2-dimethylhexane has both methyl groups on the second carbon atom of the main chain. This naming and positioning impact the molecule's properties and shape.

Carbon Chain

The carbon chain is at the heart of any organic molecule's structure. In a carbon chain, carbon atoms are linked together, forming the backbone of the molecule. In the context of dimethylhexane, the carbon chain refers to the six carbon atoms that form hexane.

Understanding carbon chains is crucial as:

• They determine the stability of the molecule.
• They influence how the molecule interacts with other compounds.
• They serve as a reference point for naming additional functional groups.

A clear grasp of carbon chains allows one to logically understand how and where methyl groups or other functional groups can be attached.

Methyl Groups

Methyl groups are one of the most basic functional groups in organic chemistry, represented as -CH₃. They are important in modifying the structure and properties of hydrocarbons like hexane. When identifying methyl groups within a molecule:

• Look for single carbon atoms bonded to three hydrogen atoms.
• Notice their placement can vary, giving rise to isomers (compounds with the same formula but different structures).

For example, in dimethylhexane, the positions of these methyl groups denote the various isomers like 2,3-dimethylhexane or 3,4-dimethylhexane, affecting not just the molecular geometry but potentially its reactions and uses.