Chapter 16: Problem 6

Draw the structures for: (a) 2,3-dichlorohexanal; (b) 4-hydroxybutanal;(c) 2 -bromo-3-pentanone; (d) 3 -methyl-2-butanone.

Short Answer

Expert verified

Draw carbon chains, add carbonyl groups, and then any substituents at the specified positions.

Step by step solution

Draw the Carbon Skeleton for Each Structure

Start by drawing the backbone for each molecule. For example, hexanal has 6 carbon atoms in a chain, butanal has 4, pentanone has 5, and butanone has 4.

Add the Functional Groups

In the case of aldehydes like hexanal and butanal, draw a carbonyl group (C=O) at the terminal carbon. For pentanone and butanone, place the carbonyl group on the appropriate carbon according to the name.

Add Any Substituents

In the molecule names, locate and add substituents. For example: 2,3-dichlorohexanal has chlorine atoms on the 2nd and 3rd carbons. Follow this pattern for each molecule.

Finalize the Structures

Verify that all carbons have four bonds and that the structures are correct. Adjust any positions as needed to ensure correctness.

Example for 2,3-Dichlorohexanal

Draw a 6-carbon chain. Add a double-bonded O to the terminal carbon. Place Cl on the 2nd and 3rd carbon.

Example for 4-Hydroxybutanal

Draw a 4-carbon chain. Add a double-bonded O to the terminal carbon. Place OH on the 4th carbon.

Example for 2-Bromo-3-Pentanone

Draw a 5-carbon chain. Add a double-bonded O to the 3rd carbon. Place Br on the 2nd carbon.

Example for 3-Methyl-2-Butanone

Draw a 4-carbon chain. Add a double-bonded O to the 2nd carbon. Add a methyl group (CH3) on the 3rd carbon.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Carbon Skeleton

The carbon skeleton forms the backbone of organic molecules. It is essentially the chain of carbon atoms that other elements attach to. Drawing this correctly is crucial:
To start, identify the number of carbons from the molecule’s name:

Hexanal has 6 carbons.
Butanal and Butanone have 4 carbons.
Pentanone has 5 carbons.

Once the carbon chain length is set, arrange them in a straight line to simplify the drawing. Ensure the carbon atoms are connected with single bonds. If any carbons form rings, follow the naming rules to depict them accurately. Understanding the basic structure without extra groups simplifies the later steps of adding functional groups and substituents.

Functional Groups

Functional groups are specific groups of atoms that impart certain chemical properties to molecules. Correct placement is key:
For aldehydes and ketones in our examples:

Hexanal and Butanal are aldehydes, so a carbonyl group (C=O) goes at the end of the chain.
Bromo-3-pentanone and methyl-2-butanone are ketones, so the carbonyl group (C=O) is located on an internal carbon.

Example breakdown:
- In 2,3-dichlorohexanal, place the carbonyl group at the end of the 6-carbon chain.
- For 4-hydroxybutanal, the carbonyl group goes at the end of the 4-carbon chain.
- 2-bromo-3-pentanone and 3-methyl-2-butanone have their carbonyl groups in the middle of the chains. This structure affects the reactivity and properties of molecules significantly
This makes it essential to practice drawing them.

Substituents

Substituents are atoms or groups of atoms attached to the carbon skeleton, modifying its properties:

Identify their positions from the molecule’s name.
2,3-dichlorohexanal has chlorine atoms on the 2nd and 3rd carbons in the 6-carbon chain.
4-hydroxybutanal has a hydroxyl (OH) group on the 4th carbon of the 4-carbon chain.
2-bromo-3-pentanone has a bromine atom on the 2nd carbon of the 5-carbon chain.
3-methyl-2-butanone has a methyl group (CH3) on the 3rd carbon of the 4-carbon chain.

It’s important to ensure that:
- All carbons have four bonds.
- Substituents are accurately placed.
Counting the carbon atoms in the chain helps with error-free placement of substituents.
Practicing the drawing and being precise with positions helps create accurate organic molecule structures.

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Draw the structures for: (a) 2,3-dichlorohexanal; (b) 4-hydroxybutanal;(c) 2 -bromo-3-pentanone; (d) 3 -methyl-2-butanone.

Short Answer

Step by step solution

Draw the Carbon Skeleton for Each Structure

Add the Functional Groups

Add Any Substituents

Finalize the Structures

Example for 2,3-Dichlorohexanal

Example for 4-Hydroxybutanal

Example for 2-Bromo-3-Pentanone

Example for 3-Methyl-2-Butanone

Key Concepts

Carbon Skeleton

Functional Groups

Substituents

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