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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9:26 minutes

Problem 55e

Textbook Question

Looking down the indicated bond, show the three most stable conformations and choose the one that is most stable. Be sure that the first Newman projection you show is the one you see initially (before rotation). [Why should none of your three Newman projections show eclipsed conformations?]
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Verified step by step guidance

Step 1: Begin by identifying the bond you are looking down in the molecule. This is typically indicated in the problem or image. Visualize the molecule in 3D space and determine the groups attached to the front and back carbons of the bond.

Step 2: Draw the initial Newman projection based on the given orientation. In a Newman projection, the front carbon is represented as a dot, and the back carbon is represented as a circle. Arrange the substituents around the front and back carbons according to their positions in the molecule.

Step 3: Rotate the bond in increments of 60° to generate the three staggered conformations. Staggered conformations occur when the substituents on the front and back carbons are spaced as far apart as possible, minimizing torsional strain. Avoid eclipsed conformations, as they result in higher energy due to steric and torsional strain.

Step 4: Evaluate the stability of each staggered conformation by considering factors such as steric hindrance (size of substituents) and electronic effects (e.g., dipole interactions). The most stable conformation will typically have the largest groups positioned anti to each other (180° apart).

Step 5: Choose the most stable conformation based on your evaluation. This conformation minimizes steric and torsional strain, making it the lowest-energy arrangement. Ensure that none of the Newman projections you draw show eclipsed conformations, as these are energetically unfavorable.

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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 a bond connecting two carbon atoms. This representation helps in analyzing the spatial arrangement of substituents around the bond, allowing for the identification of different conformations, such as staggered and eclipsed forms.

Staggered vs. Eclipsed Conformations

In organic chemistry, staggered conformations occur when substituents on adjacent carbons are positioned as far apart as possible, minimizing steric strain. In contrast, eclipsed conformations have substituents aligned with each other, leading to increased steric hindrance and torsional strain, making them less stable than staggered conformations.

Conformational Stability

Conformational stability refers to the relative energy levels of different molecular conformations. Generally, staggered conformations are more stable due to lower energy states compared to eclipsed conformations, which are higher in energy due to increased steric interactions. Understanding this concept is crucial for predicting the most stable conformation in a given molecular structure.

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Textbook Question

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

c. 3,3-dimethylhexane, viewed along the C-3---C-4 bond

Textbook Question

For the following molecule, draw the Newman projection (around the 2,3-bond) with a dihedral angle of 180° between the bromine and hydrogen.

Textbook Question

Conformational studies on ethane-1,2-diol (HOCH₂–CH₂OH) have shown the most stable conformation about the central C―C bond to be the gauche conformation, which is 9.6 kJ/mol (2.3 kcal/mol) more stable than the anti conformation. Draw Newman projections of these conformers, and explain this curious result.

Textbook Question

Draw the conformer that is present in greatest concentration.

Multiple Choice

Draw the most energetic Newman Projection of CH₃CH(C₆H₅)CH₃

Multiple Choice

Draw the most stable Newman Projection of CH₃CH₂ CH₂OH through the C2 – C1 bond.

Multiple Choice

Which line-angle structure matches the Newman projection, when looking from the right?

Textbook Question

Use a Newman projection about the indicated bond to draw the most stable conformer for each compound.

a. 3-methylpentane about the C2―C3 bond

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