Question

Draw and name all monochloro derivatives of 2,5 -dimethylhexane, \(\mathrm{C}_{8} \mathrm{H}_{17} \mathrm{Cl}\)

Short answer

There are six monochloro derivatives: 1-, 2-, 3-, 4-, 5-, 6-chloro-2,5-dimethylhexane.

Step-by-step solution

Understand the Parent Compound

2,5-dimethylhexane is the parent compound with the molecular formula \(\mathrm{C}_{8}\mathrm{H}_{18}\). It is a branched alkane with a six-carbon chain and two methyl groups attached at the second and fifth carbons.

Identify Possible Substitution Sites

Identify the hydrogen atoms on the parent compound that can be replaced by a chlorine atom. 2,5-dimethylhexane has a total of eight carbon atoms: two are primary (attached to only one other carbon), four are secondary (attached to two other carbons), and none are tertiary or quaternary.

Determine Mono-substitution Positions

For each type of carbon (primary, secondary), consider replacing a single hydrogen with a chlorine atom. This replacement will produce different isomers.

Draw the Structural Isomers

1. Replace a hydrogen on the primary carbon: Produces 1-chloro-2,5-dimethylhexane and 6-chloro-2,5-dimethylhexane. 2. Replace a hydrogen on the secondary carbon: Produces 2-chloro-2,5-dimethylhexane, 3-chloro-2,5-dimethylhexane, 4-chloro-2,5-dimethylhexane, and 5-chloro-2,5-dimethylhexane.

Name Each Isomer

The possible monochloro derivatives, based on their structural positions, are: 1. 1-chloro-2,5-dimethylhexane 2. 2-chloro-2,5-dimethylhexane 3. 3-chloro-2,5-dimethylhexane 4. 4-chloro-2,5-dimethylhexane 5. 5-chloro-2,5-dimethylhexane 6. 6-chloro-2,5-dimethylhexane.

Key concepts

Structural Isomers

In organic chemistry, structural isomers are molecules with the same molecular formula but different structural arrangements of atoms. This results in isomers having different physical and chemical properties, even though they share the same basic composition. Think of structural isomers as different blueprints for a building, where each blueprint uses the same materials but organises them in unique patterns.
When we talk about organic molecules, "structures" often relate to the chain of carbon atoms.

• The way these carbon atoms are arranged can change the molecule's shape and affect how it behaves in reactions.
• Structural isomers can occur because the carbon chains can branch in varied ways or because functional groups can be positioned differently.

For example, in 2,5-dimethylhexane, the methyl groups can be on various carbon atoms, creating different isomeric possibilities. Understanding isomers is crucial for predicting how molecules behave in chemical reactions and in various environments.

Monochloro Derivatives

Monochloro derivatives are compounds formed when one hydrogen atom in an alkane is replaced with a chlorine atom. This substitution results in a halogenated alkane, commonly known as alkyl chlorides. These transformations are significant in organic synthesis, as they often serve as intermediates in more complex reactions.
In the case of 2,5-dimethylhexane, a single chlorine can replace a hydrogen atom in different locations, leading to different monochloro derivatives.

• These derivatives are vital because their properties and reactivity change depending on the chlorine's position.
• For instance, position on a primary carbon may result in different reactivity compared to a secondary carbon.

By examining monochloro derivatives, one can better appreciate how even subtle changes in molecular structure can lead to different chemical behaviors.

Alkane Substitution

Alkane substitution involves the replacement of a hydrogen atom in an alkane molecule with another atom or group of atoms. Chlorination is a common type of substitution, where hydrogen is replaced with a chlorine atom, producing chloroalkanes. This process is fundamental in organic chemistry, as it provides pathways to more complex molecules through various chemical reactions.
For 2,5-dimethylhexane, substitution reactions can occur at primary or secondary carbons.

• Primary carbons are attached to only one other carbon atom, whereas secondary carbons are attached to two.
• Replacing hydrogen at these sites gives us different isomers with unique properties, influenced by the type of carbon where substitution occurs.

Alkane substitution is an essential concept for designing synthetic pathways in industrial and laboratory settings.

IUPAC Nomenclature

The International Union of Pure and Applied Chemistry (IUPAC) nomenclature provides a systematic way to name chemical compounds, ensuring clarity and uniformity in chemical communication worldwide. In the context of organic compounds like alkanes and their derivatives, IUPAC names help predict the structure and functional groups present in a molecule efficiently.
When naming monochloro derivatives of 2,5-dimethylhexane:

• The position of the chlorine atom is indicated by a number corresponding to the carbon atom it is attached to.
• The name begins with the position of the chlorine, followed by "chloro", and ends with the parent alkane's name with appropriate methyl groups placement.

This method allows chemists to deduce the molecular structure's blueprint from the name alone. For instance, "3-chloro-2,5-dimethylhexane" specifies that chlorine is attached to the third carbon. Understanding and using IUPAC nomenclature is crucial for identifying, understanding, and communicating chemical structures and their transformations.