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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4:35 minutes

Problem 6

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.

Verified step by step guidance

Identify the 2,3-bond in the given molecule. This bond will serve as the axis for the Newman projection. Assign the carbon at position 2 as the front carbon and the carbon at position 3 as the rear carbon for the projection.

Determine the substituents attached to the front carbon (C-2). These substituents will radiate outward from the center of the Newman projection. Label them clearly (e.g., bromine, hydrogen, and any other group).

Determine the substituents attached to the rear carbon (C-3). These substituents will also radiate outward but will be drawn behind the front carbon in the Newman projection. Label them clearly (e.g., hydrogen and any other groups).

Position the substituents such that the dihedral angle between the bromine on the front carbon and the hydrogen on the rear carbon is 180°. This means they should be directly opposite each other in the Newman projection (anti-periplanar arrangement).

Draw the Newman projection with the front carbon substituents arranged in a Y-shape and the rear carbon substituents arranged in a circle behind it. Ensure the bromine and hydrogen are anti to each other, and label all substituents for clarity.

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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 way of visualizing the conformation of a molecule by looking straight down the bond connecting two carbon atoms. This representation helps in understanding the spatial arrangement of substituents around the bond, which is crucial for analyzing steric interactions and torsional strain in organic molecules.

Dihedral Angle

The dihedral angle is the angle between two planes formed by four atoms in a molecule. In the context of a Newman projection, it describes the relative orientation of substituents on adjacent carbon atoms. A dihedral angle of 180° indicates that the substituents are in an anti conformation, which is often more stable due to minimized steric hindrance.

Steric Hindrance

Steric hindrance refers to the repulsion between atoms that occurs when they are brought close together, affecting the stability and reactivity of a molecule. In the context of the Newman projection, understanding steric hindrance is essential for predicting the most stable conformations, as bulky groups can create unfavorable interactions when positioned too closely.

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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?]

(b) <IMAGE>

Textbook Question

For each of the following structures, which staggered Newman projection skeleton from Assessment 3.51 should you draw first to show what is seen when looking down the indicated bond?

(d) <IMAGE>

Textbook Question

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

(c)

(d)

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

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.

Textbook Question

(e) <IMAGE>

Multiple Choice

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

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