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.
1
views
Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
All textbooks
Bruice 8th EditionCh. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and StructureProblem 42a
Bruice 8th EditionCh. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and StructureProblem 42aChapter 4, Problem 42a
Using Newman projections, draw the most stable conformer for each of the following:
a. 3-methylpentane, viewed along the C-2---C-3 bond
Verified step by step guidance1
Step 1: Understand the Newman projection concept. A Newman projection is a way to visualize the conformations of a molecule by looking directly down a specific bond axis. In this case, we are viewing along the C-2-C-3 bond of 3-methylpentane.
Step 2: Identify the substituents attached to the C-2 and C-3 atoms. For 3-methylpentane, C-2 has a hydrogen atom, a methyl group (-CH3), and the rest of the chain (-CH2CH2CH3). C-3 has a hydrogen atom, a methyl group (-CH3), and the rest of the chain (-CH2CH3).
Step 3: Draw the front carbon (C-2) as a circle and place its substituents (hydrogen, methyl group, and chain) at 120° angles around the circle. The back carbon (C-3) is represented as a larger circle behind the front carbon, with its substituents also placed at 120° angles.
Step 4: Arrange the substituents to minimize steric hindrance and achieve the most stable staggered conformation. In a staggered conformation, the substituents on the front and back carbons are positioned as far apart as possible. Place the bulky groups (methyl groups and chains) opposite each other to reduce steric interactions.
Step 5: Verify the stability of the conformer. Ensure that the largest groups (methyl groups and chains) are anti-periplanar (180° apart) to achieve the most stable configuration. Smaller groups like hydrogen atoms can occupy the closer positions (gauche interactions).
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2mWas this helpful?
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 steric interactions and torsional strain between substituents attached to the carbons. By rotating around the bond, different conformers can be depicted, allowing for the identification of the most stable arrangement.
Recommended video:
Guided course
00:34
Introduction to Drawing Newman Projections
Conformational Stability
Conformational stability refers to the relative energy of different spatial arrangements of a molecule. Factors influencing stability include steric hindrance, torsional strain, and the presence of electron-donating or withdrawing groups. In the case of 3-methylpentane, the most stable conformer minimizes steric clashes between the bulky methyl group and other hydrogen atoms.
Recommended video:
Guided course
03:29Understanding what a conformer is.
Steric Hindrance
Steric hindrance occurs when atoms or groups within a molecule are in close proximity, leading to repulsive interactions that increase the energy of the system. In conformational analysis, minimizing steric hindrance is crucial for identifying the most stable conformer. For 3-methylpentane, the arrangement that places the methyl group in an equatorial position relative to other substituents typically results in lower steric strain.
Recommended video:
Guided course
02:53Understanding steric effects.
Related Practice
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
1
views
Textbook Question
Draw all the staggered and eclipsed conformers that result from rotation about the C-2-C-3 bond of pentane.
1
views
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
2
views
Textbook Question
Convert the following Newman projections to skeletal structures and name them.
a.
b.
1
views
Textbook Question
The bond angles in a regular polygon with n sides are equal to 180° - 360°/n
a. What are the bond angles in a regular octagon?
b. What are the bond angles in a regular nonagon?
1
views