Write a structural formula for each of the following compounds

Write a structural formula for each of the following compounds:

(a) 6-Isopropyl-2,3-dimethylnonane

(b) 4 -tert-Butyl-3-methylheptane

(c) 4-Isobutyl-1,1-dimethylcyclohexane

(d) sec-Butylcycloheptane

(e) Cyclobutylcyclopentane

The correct answer and explanation is:

Let’s break down each compound and construct their structural formulas:

(a) 6-Isopropyl-2,3-dimethylnonane

This compound has the following components:

  • A nonane backbone (C9 chain)
  • At position 6, there’s an isopropyl group (–CH(CH3)2)
  • At positions 2 and 3, there are methyl groups (–CH3)

The structure can be represented as:

CH3-CH2-CH(CH3)-CH(CH3)-CH2-CH(CH3)-CH2-CH3

In this structure, the longest carbon chain is nine atoms long (nonane). At positions 2 and 3, there are methyl groups, and an isopropyl group is attached at position 6.

(b) 4-tert-Butyl-3-methylheptane

This compound has:

  • A heptane backbone (C7 chain)
  • A tert-butyl group (–C(C3H7)3) at position 4
  • A methyl group (–CH3) at position 3

The structure would look like this:

CH3-CH(CH3)-CH(CH3)-C(C3H7)-CH2-CH3

In this structure, the heptane chain is modified by the tert-butyl group at position 4 and a methyl group at position 3.

(c) 4-Isobutyl-1,1-dimethylcyclohexane

This compound involves:

  • A cyclohexane ring (C6H12)
  • An isobutyl group (–CH2CH(CH3)2) at position 4
  • Two methyl groups (–CH3) at position 1

The structure would be:

    CH3
     |
CH3-C-CH2-C6H10
     |
    CH2CH3

The cyclohexane ring has methyl groups at position 1 and an isobutyl group at position 4.

(d) sec-Butylcycloheptane

This compound consists of:

  • A cycloheptane ring (C7H14)
  • A sec-butyl group (–CH2CH(CH3)2) attached to the ring

The structure would be:

     CH3
      |
CH3-CH2-C-C7H12
      |
     CH2CH3

Here, the cycloheptane ring is attached to a sec-butyl group at one of its positions.

(e) Cyclobutylcyclopentane

This compound consists of:

  • A cyclobutyl group (C4H7)
  • A cyclopentane ring (C5H10)

The structure looks like this:

   C4H7
    |
C5H10-C

In this case, a cyclobutyl group is fused to a cyclopentane ring.

Explanation

The key to understanding these structures lies in interpreting the names based on IUPAC nomenclature, where the position and type of side groups (methyl, isopropyl, tert-butyl, etc.) determine how they are attached to the parent chain or ring. A cycloalkane is a ring structure, and the functional groups or substituents are positioned according to their number in the name.

In the case of sec-butyl and isobutyl groups, these refer to branching arrangements that alter the structure of the main chain. The tert-butyl group is a highly branched form of butyl, and these arrangements help us determine the proper attachment points in the structure.

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