Textbook Question
What alkene could you use to make the following products? Draw the structure of the alkene, and tell what other reagent is also required for the reaction to occur.
c.
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Ch.13 Alkenes, Alkynes, and Aromatic Compounds
McMurry8th EditionFundamentals of GOBISBN: 9780134015187
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Table of contents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
Chapter 13, Problem 62
1-Pentyne reacts with HBr in a 1:1 molar ratio to yield two different addition products, both being bromopentenes and having the chemical formula C5H9Br. Draw the structures of two possible products.
Verified step by step guidance1
Identify the structure of 1-pentyne, which is a terminal alkyne with the molecular formula C₅H₈. Its structure consists of a triple bond between the first and second carbon atoms in a five-carbon chain.
Understand the reaction mechanism: The addition of HBr to an alkyne follows Markovnikov's rule, where the hydrogen atom adds to the carbon with more hydrogens, and the bromine atom adds to the carbon with fewer hydrogens. However, in this case, the reaction can proceed in two steps, leading to two different products.
For the first product, consider the addition of HBr to the triple bond to form a double bond. The hydrogen atom adds to the terminal carbon (C1), and the bromine atom adds to the adjacent carbon (C2), resulting in 2-bromo-1-pentene.
For the second product, consider the possibility of anti-Markovnikov addition due to the presence of radicals or other reaction conditions. In this case, the hydrogen atom adds to the C2 carbon, and the bromine atom adds to the terminal carbon (C1), resulting in 1-bromo-2-pentene.
Draw the structures of the two products: (1) 2-bromo-1-pentene, where the bromine is attached to the second carbon and the double bond is between C1 and C2, and (2) 1-bromo-2-pentene, where the bromine is attached to the first carbon and the double bond is between C2 and C3.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkyne Reactivity
Alkynes, such as 1-pentyne, are hydrocarbons with at least one carbon-carbon triple bond. They undergo electrophilic addition reactions, where reagents like HBr add across the triple bond. This reactivity is crucial for understanding how 1-pentyne can form different products when reacting with HBr.
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Naming Alkynes Example 1
Markovnikov's Rule
Markovnikov's Rule states that in the addition of HX to an alkene or alkyne, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This principle helps predict the major product in reactions involving unsymmetrical alkenes or alkynes, leading to the formation of different bromopentenes in this case.
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Stereochemistry of Addition Reactions
Stereochemistry refers to the spatial arrangement of atoms in molecules. In the case of 1-pentyne reacting with HBr, the addition can lead to different stereoisomers, depending on the orientation of the bromine and hydrogen atoms. Understanding stereochemistry is essential for accurately drawing the structures of the resulting bromopentenes.
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Related Practice
Textbook Question
What alkene could you use to make the following products? Draw the structure of the alkene, and tell what other reagent is also required for the reaction to occur.
d.
871
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Textbook Question
2,2,3,3-Tetrabromopentane can be prepared by an addition reaction of excess Br2 with an alkyne. Draw the structure of the alkyne and name it.
677
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Textbook Question
Polyvinylpyrrolidone (PVP) is often used in hair sprays to hold hair in place. Draw a few units of the PVP polymer. The vinylpyrrolidone monomer unit has the following structure:
34
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Textbook Question
For each of the following reagents, decide whether chlorobenzene will react with it or not, and, if it does, draw and name the products expected from the reaction.
c. HNO3 and H2SO4 catalyst
37
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Textbook Question
Aromatic compounds do not normally react with hydrogen in the presence of a palladium catalyst but will if very high pressures (200 atm) and high temperatures are used. Under these conditions, toluene adds three molecules of H2 to give an alkane addition product. What is a likely structure for the product?
744
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