Textbook Question
1. Draw the structure of cis-CH3CH=CHCH2CH3 showing the pi bond with its proper geometry.2. Draw the trans isomer, and circle the coplanar atoms. Are there still six?
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Ch. 7 - Structure and Synthesis of Alkenes; Elimination
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 7, Problem 1a
If a hydrocarbon has nine carbon atoms, three double bonds, and one ring, how many hydrogen atoms must it have?
Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)
C = number of carbons
H = number of hydrogens
Verified step by step guidance1
Start by understanding the concept of elements of unsaturation. This concept helps determine the degree of unsaturation in a molecule, which includes rings and multiple bonds (double or triple bonds). Each ring or double bond counts as one element of unsaturation.
Identify the elements of unsaturation in the given hydrocarbon. The problem states there are three double bonds and one ring. Therefore, the total elements of unsaturation is 4.
Use the formula for elements of unsaturation: \( \text{Elements of Unsaturation} = \frac{1}{2}(2C + 2 - H) \). Substitute the known values: \( C = 9 \) and \( \text{Elements of Unsaturation} = 4 \).
Set up the equation based on the formula: \( 4 = \frac{1}{2}(2 \times 9 + 2 - H) \). Simplify the expression inside the parentheses: \( 2 \times 9 + 2 = 20 \).
Solve for \( H \) by isolating it in the equation: \( 4 = \frac{1}{2}(20 - H) \). Multiply both sides by 2 to eliminate the fraction: \( 8 = 20 - H \). Rearrange to find \( H \): \( H = 20 - 8 \).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hydrocarbon Structure
Hydrocarbons are organic compounds consisting entirely of hydrogen and carbon. The structure of a hydrocarbon can include chains, rings, and multiple bonds, which affect the number of hydrogen atoms present. Understanding the arrangement of carbon atoms and the presence of rings or double bonds is crucial for determining the molecular formula.
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Aromaticity of Hydrocarbons
Elements of Unsaturation
Elements of unsaturation refer to the presence of double bonds, triple bonds, or rings in a molecule, which reduce the number of hydrogen atoms compared to a saturated hydrocarbon. The formula 1/2(2C + 2 - H) calculates the degree of unsaturation, helping to determine the number of hydrogen atoms in a compound with given carbon atoms and unsaturation elements.
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02:39The difference between saturated and unsaturated molecules.
Molecular Formula Calculation
To find the number of hydrogen atoms in a hydrocarbon, use the elements of unsaturation formula. For a hydrocarbon with nine carbon atoms, three double bonds, and one ring, calculate the unsaturation and adjust the hydrogen count accordingly. This involves understanding how each double bond and ring affects the hydrogen count compared to a fully saturated hydrocarbon.
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Related Practice
Textbook Question
Give five examples of structures with this formula (C6H12). At least one should contain a ring, and at least one should contain a double bond.
Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)
C = number of carbons
H = number of hydrogens
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Textbook Question
Calculate the number of elements of unsaturation implied by the molecular formula C6H12.
Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)
C = number of carbons
H = number of hydrogens
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Textbook Question
Determine the number of elements of unsaturation in the molecular formula C4H6. Give all nine possible structures having this formula. Remember that
a double bond = one element of unsaturation
a ring = one element of unsaturation
a triple bond = two elements of unsaturation
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