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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2:26 minutes

Problem 44a

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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Identify the structure of 3-methylpentane. It is a branched alkane with a methyl group attached to the third carbon of a pentane chain.

Draw the skeletal structure of 3-methylpentane, focusing on the C2―C3 bond. The carbon atoms are numbered from the end closest to the branch, so C2 is the second carbon in the chain, and C3 is the third.

Visualize the Newman projection by looking down the C2―C3 bond. In a Newman projection, the front carbon (C2) is represented by a dot, and the back carbon (C3) is represented by a circle.

Arrange the substituents around the C2 and C3 carbons. For C2, you have a hydrogen, a methyl group, and the rest of the pentane chain. For C3, you have two hydrogens and the methyl group from the branch.

Determine the most stable conformer by rotating the groups around the C2―C3 bond to minimize steric hindrance. Typically, staggered conformations are more stable than eclipsed ones. Position the largest groups (methyl groups) as far apart as possible to achieve the most stable staggered conformation.

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Key Concepts

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

Newman Projection

A Newman projection is a method used in organic chemistry to visualize the conformation of a molecule from a specific viewpoint, typically along a carbon-carbon bond axis. It helps in understanding the spatial arrangement of atoms and the steric interactions that influence molecular stability.

Conformational Analysis

Conformational analysis involves studying the different spatial arrangements of atoms in a molecule that result from rotation around single bonds. It is crucial for determining the most stable conformer, which minimizes steric hindrance and torsional strain, often leading to the lowest energy state.

Steric Hindrance

Steric hindrance refers to the repulsion between atoms or groups of atoms due to their size and spatial arrangement, affecting molecular stability. In conformational analysis, minimizing steric hindrance is key to identifying the most stable conformer, as larger groups prefer positions that reduce crowding.

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Related Practice

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?]

(e) <IMAGE>

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.

b. 3,3-dimethylhexane about the C3―C4 bond

Textbook Question

Convert each Newman projection to the equivalent line–angle formula, and assign the IUPAC name. g.

(g)

(h)

Textbook Question

Convert each Newman projection to the equivalent line–angle formula, and assign the IUPAC name.

(a)

(b)

Textbook Question

Draw a Newman projection, similar to Figure 3-25 down the C1—C6 bond in the equatorial conformation of methylcyclohexane. Show that the equatorial methyl group is also anti to C5. (Using your models will help.)

<IMAGE>

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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

Key Concepts

Newman Projection

Conformational Analysis

Steric Hindrance

Watch next

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