Problem 202 - A Complete Resource Book in Chemistry for JEE Main

Question

The IUPAC name of CC1(C)CCCC(O)C1 is (a) 3,3 -dimethyl-1-hydroxycyclohexane (b) 1,1 -dimethyl-3-hydroxycyclohexane (c) 3,3 -dimethyl-1-cyclohexanol (d) 1,1 -dimethyl-3-cyclohexanol

Step-by-Step Solution

Answer

The IUPAC name is 3,3-dimethyl-1-cyclohexanol.

Step 1: Identify the Parent Hydrocarbon

The structure is a cyclohexane ring, identified by the six-membered carbon ring. This forms the parent hydrocarbon base for naming.

Step 2: Identify Substituents

Identify the functional groups attached to the cyclohexane ring. We see a hydroxyl group (-OH) and two additional methyl groups attached.

Step 3: Determine Substituent Position

Assign positions on the cyclohexane such that the hydroxyl group gets the lowest possible number, as it is the highest priority substituent. Here, the hydroxyl group is at position 1.

Step 4: Assign Numbers to Other Substituents

Identify the positions of the two methyl groups. Since the hydroxyl is at position 1, the lowest position numbers for two identical groups would be at carbon 3.

Step 5: Compile the IUPAC Name

With the hydroxyl group and methyl groups at positions 1 and 3, respectively, the IUPAC name becomes 3,3-dimethyl-1-cyclohexanol.

Key Concepts

Hydroxyl Group Identification

When identifying functional groups in a chemical structure, the hydroxyl group is a common one to spot. This group is characterized by the presence of an oxygen and hydrogen atom bonded together, often represented as -OH in chemical formulas. The presence of a hydroxyl group is key to classifying a compound as an alcohol.

In IUPAC nomenclature, hydroxyl groups hold a higher priority over other types of substituents, such as alkyl groups. This priority affects how the structure is numbered, as the hydroxyl group should be given the lowest possible position number. Recognizing this group correctly is crucial for determining the accurate naming and properties of the compound. Ensuring that you locate the hydroxyl group first will facilitate naming and ensure you don't overlook its importance in terms of structural priorities.

Cyclohexane Structure

Cyclohexane is a type of hydrocarbon that forms a ring structure composed of six carbon atoms. This structure is saturated, meaning it only contains single bonds between carbon atoms, giving it the formula C₆H₁₂. Identifying cyclohexane in chemical structures is pivotal as it forms the backbone for many other complex organic molecules.

The distinct ring shape of cyclohexane is not perfectly planar; instead, it adopts a chair-like conformation that minimizes the torsional strain by allowing the hydrogen atoms to be staggered, not eclipsing each other.

• The ring structure can potentially host various substituents, affecting the overall properties and reactivity of the molecule.
• Naming of substituents within a cyclohexane structure often considers both the position and the type of each group attached.

Recognizing cyclohexane and understanding its structure allows for a clearer understanding of organic compounds and their systematic naming using IUPAC guidelines.

Methyl Group Positioning

Positioning substituents on a ring structure like cyclohexane is integral to determining the correct IUPAC name. In the case of methyl groups, these are simple alkyl groups consisting of just a single carbon bonded to three hydrogens, represented as -CH₃.

To correctly name a compound, the position of each methyl group must be identified and numbered appropriately on the parent structure. The IUPAC rules dictate that the numbering should ensure the substituents have the lowest possible numbers, reflecting their priority.

• Methyl groups attached to cyclohexane are numbered based on their impact on the overall molecular symmetry and the priority of other substituents like hydroxyl groups.
• In our example, to minimize numerical position, the two methyl groups are positioned at carbons with the lowest numbers after assigning position 1 to the hydroxyl group.

Understanding the nuances of methyl group positioning aids in following the correct protocol for naming, ensuring clarity and consistency in chemical communication.