Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

4. Alkanes and Cycloalkanes

Drawing Newman Projections

Organic Chemistry

4. Alkanes and Cycloalkanes

Drawing Newman Projections

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3:49 minutes

Problem 42b

Textbook Question

Using Newman projections, draw the most stable conformer for each of the following:
b. 3-methylhexane, viewed along the C-3----C-4 bond

Verified step by step guidance

Identify the structure of 3-methylhexane and locate the C-3 and C-4 atoms in the molecule. The C-3 atom is bonded to a methyl group (-CH₃), a hydrogen atom, and the rest of the chain, while the C-4 atom is bonded to two hydrogens and the rest of the chain.

Understand that Newman projections are a way to visualize the conformations of a molecule by looking down a specific bond axis. In this case, you will be viewing along the C-3-C-4 bond.

Draw the front carbon (C-3) as a circle and the back carbon (C-4) as a larger circle behind it. Represent the substituents on C-3 (methyl group, hydrogen, and the chain) as lines radiating from the center of the front circle, and the substituents on C-4 (two hydrogens and the chain) as lines radiating from the back circle.

To determine the most stable conformer, arrange the substituents such that bulky groups (like the methyl group and the chain) are staggered, minimizing steric hindrance. In a staggered conformation, the substituents on the front carbon are positioned at 60° angles relative to the substituents on the back carbon.

Verify that the methyl group on C-3 and the chain on C-4 are positioned opposite each other in the staggered conformation to achieve the lowest energy state. This arrangement minimizes steric interactions between the bulky groups.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Newman Projections

Newman projections are a way to visualize the conformation of a molecule by looking straight down the bond connecting two carbon atoms. This representation helps in analyzing steric interactions and torsional strain between substituents attached to the carbons, allowing chemists to identify the most stable conformations based on the spatial arrangement of these groups.

Conformational Stability

Conformational stability refers to the relative energy of different spatial arrangements of a molecule. In alkanes, factors such as steric hindrance and torsional strain influence stability. The most stable conformer is typically the one that minimizes these interactions, often achieved by positioning bulky groups in staggered arrangements rather than eclipsed ones.

Substituent Effects in Alkanes

In branched alkanes like 3-methylhexane, the presence and position of substituents significantly affect the molecule's conformation. Larger substituents can create steric hindrance, which influences the stability of different conformers. Understanding how these substituents interact in a Newman projection is crucial for determining the most stable conformation.

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Related Practice

Textbook Question

Draw Newman projections of the following molecules viewed from the direction of the blue arrows.

(b)

Textbook Question

Draw Newman projections of the following molecules viewed from the direction of the blue arrows.

(a)

Textbook Question

Convert the following Newman projections to skeletal structures and name them.

Textbook Question

Draw all the staggered and eclipsed conformers that result from rotation about the C-2-C-3 bond of pentane.

Textbook Question

Using Newman projections, draw the most stable conformer for each of the following:

a. 3-methylpentane, viewed along the C-2---C-3 bond

Textbook Question

Draw a potential-energy diagram for rotation about the C-2---C-3 bond of pentane through 360°, starting with the least stable conformer.

Textbook Question

For rotation about the C-3---C-4 bond of 2-methylhexane, do the following:

a. Draw the Newman projection of the most stable conformer.

b. Draw the Newman projection of the least stable conformer.

Textbook Question

c. Draw Newman projections of the two conformers of the trans isomer.

d. Which of the conformers predominates at equilibrium?

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Using Newman projections, draw the most stable conformer for each of the following: b. 3-methylhexane, viewed along the C-3----C-4 bond

Key Concepts

Newman Projections

Conformational Stability

Substituent Effects in Alkanes

Watch next

Using Newman projections, draw the most stable conformer for each of the following:
b. 3-methylhexane, viewed along the C-3----C-4 bond