Textbook Question
For each molecular formula, draw all the isomeric alkynes, and give their IUPAC names. Circle the acetylenic hydrogen of each terminal alkyne.
(a) C5H8 (three isomers)
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Ch.9 - Alkynes
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 9, Problem 2b
For each molecular formula, draw all the isomeric alkynes, and give their IUPAC names. Circle the acetylenic hydrogen of each terminal alkyne.
(b) C6H10 (seven isomers)
Verified step by step guidance1
Identify the degree of unsaturation for the molecular formula C6H10. Use the formula: Degree of Unsaturation = (2C + 2 + N - H - X) / 2, where C is the number of carbons, N is the number of nitrogens, H is the number of hydrogens, and X is the number of halogens. For C6H10, the degree of unsaturation is 2, indicating the presence of two pi bonds or rings.
Recognize that alkynes contain a carbon-carbon triple bond, which accounts for two degrees of unsaturation. Therefore, each isomer must contain one triple bond.
Draw the possible carbon skeletons for C6H10 that can accommodate a triple bond. Consider linear and branched structures, ensuring that each structure has six carbon atoms and one triple bond.
For each carbon skeleton, place the triple bond in different positions to generate distinct isomers. Ensure that each structure adheres to the valency rules of carbon, with each carbon forming four bonds.
Assign IUPAC names to each isomer by identifying the longest carbon chain containing the triple bond, numbering the chain from the end nearest the triple bond, and using the appropriate suffix '-yne'. For terminal alkynes, circle the hydrogen attached to the terminal carbon of the triple bond, known as the acetylenic hydrogen.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Isomerism
Isomerism refers to the phenomenon where compounds have the same molecular formula but different structural arrangements. In organic chemistry, structural isomers differ in the connectivity of atoms, leading to distinct properties and names. Understanding isomerism is crucial for identifying all possible configurations of a given molecular formula, such as C6H10.
Alkynes
Alkynes are hydrocarbons characterized by at least one carbon-carbon triple bond, denoted as -C≡C-. This triple bond imparts unique chemical properties, such as linear geometry and increased reactivity compared to alkenes and alkanes. Recognizing the presence of triple bonds is essential for drawing and naming alkyne isomers correctly.
IUPAC Nomenclature
IUPAC nomenclature is a standardized system for naming chemical compounds, ensuring clarity and consistency. For alkynes, the name reflects the longest carbon chain containing the triple bond, with the position of the bond indicated by a number. Mastery of IUPAC rules is necessary for accurately naming each isomeric alkyne derived from C6H10.
Related Practice
Textbook Question
The boiling points of hex-1-ene (64 °C) and hex-1-yne (71 °C) are sufficiently close that it is difficult to achieve a clean separation by distillation. Show how you might use the acidity of hex-1-yne to remove the last trace of it from a sample of hex-1-ene.
Textbook Question
Count the elements of unsaturation in parsalmide, ethynyl estradiol, and dynemicin A.
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Textbook Question
Draw structural formulas of at least two alkynes of each molecular formula.
1. C6H10
2. C8H12
3. C7H8
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Textbook Question
Predict the products of the following acid–base reactions, or indicate if no significant reaction would take place.
a. H—C≡C—H + NaNH2
b. H—C≡C—H + CH3Li
c. H—C≡C—H + NaOCH3
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Textbook Question
What reaction would acetylene likely undergo if it were kept at 1500°C for too long?
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