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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3:45 minutes

Problem 76b

Textbook Question

Draw the conformer that is present in greatest concentration.

Verified step by step guidance

Understand the concept of conformers: Conformers are different spatial arrangements of a molecule that result from rotation around single bonds. The conformer present in the greatest concentration is typically the one with the lowest energy.

Identify the molecule in question: Determine the structure of the molecule and locate any single bonds that allow for rotation. This will help you visualize the possible conformers.

Evaluate steric hindrance: Analyze the interactions between substituents or groups attached to the molecule. Conformers with less steric hindrance (less crowding of atoms) are generally more stable and present in higher concentrations.

Consider electronic effects: If the molecule has polar groups or dipoles, assess how their arrangement affects stability. Conformers with favorable dipole-dipole interactions or minimized repulsion are more stable.

Draw the most stable conformer: Based on steric and electronic considerations, sketch the conformer with the lowest energy. Ensure that bulky groups are positioned in a way that minimizes repulsion, such as in an anti-periplanar or staggered arrangement for alkanes.

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Key Concepts

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

Conformational Analysis

Conformational analysis involves studying the different spatial arrangements of a molecule that can be interconverted by rotation around single bonds. These arrangements, known as conformers, can significantly influence the molecule's stability and reactivity. Understanding the energy differences between conformers helps predict which form is most prevalent under specific conditions.

Stability of Conformers

The stability of conformers is determined by factors such as steric strain, torsional strain, and angle strain. Conformers that minimize steric hindrance and torsional strain are generally more stable. For example, in alkanes, staggered conformations are typically more stable than eclipsed ones due to reduced electron repulsion between adjacent bonds.

Equilibrium and Concentration

In a dynamic equilibrium, different conformers of a molecule exist in varying concentrations based on their relative stabilities. The conformer with the lowest energy is usually present in the greatest concentration. Understanding how to draw and analyze these conformers allows chemists to predict the predominant form of a molecule in a given environment.

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Related Practice

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

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

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?

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