Textbook Question
For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (ii) H2, Pd/C, Pb(OAc)2 , CaCO3 (Lindlar's catalyst). If you expect two products, show both.
(c)
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Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
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Mullins 1st EditionCh. 10 - Alkynes: Electrophilic Addition and Redox ReactionsProblem 44c(viii)
Mullins 1st EditionCh. 10 - Alkynes: Electrophilic Addition and Redox ReactionsProblem 44c(viii)Chapter 9, Problem 44c(viii)
For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (viii) Cl2 (1 equiv.). If you expect two products, show both.
(c) 
Verified step by step guidance1
Identify the alkyne structure provided in the problem. Alkynes are hydrocarbons containing a carbon-carbon triple bond (C≡C). Determine if the alkyne is terminal (triple bond at the end of the chain) or internal (triple bond within the chain).
Understand the reagent and reaction conditions: Cl₂ (1 equiv.) indicates that one equivalent of chlorine (Cl₂) will react with the alkyne. This is a halogenation reaction, where the alkyne reacts with halogens to form dihaloalkenes.
Recognize the mechanism: The reaction proceeds via an anti-addition mechanism. The Cl₂ molecule adds across the triple bond, breaking one π-bond of the alkyne and forming a double bond (C=C). The two chlorine atoms attach to the carbons of the former triple bond in a trans (anti) configuration.
Determine the stereochemistry and regioselectivity: Since the reaction is anti-addition, the two chlorine atoms will be added to opposite sides of the double bond. If the alkyne is symmetrical, only one product will form. If the alkyne is asymmetrical, two stereoisomers (E and Z) may form.
Draw the product(s): For a symmetrical alkyne, draw the single dihaloalkene product with the chlorine atoms in a trans configuration. For an asymmetrical alkyne, draw both possible stereoisomers (E and Z) of the dihaloalkene, showing the placement of the chlorine atoms and the double bond.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkynes
Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond. They are unsaturated compounds and are generally more reactive than alkenes and alkanes due to the presence of the triple bond. This reactivity allows them to undergo various addition reactions, including halogenation, where halogens like Cl₂ can add across the triple bond.
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Alkyne Hydration
Halogenation of Alkynes
Halogenation is a reaction where halogens, such as chlorine (Cl₂), react with unsaturated hydrocarbons. In the case of alkynes, the addition of Cl₂ can lead to the formation of dihaloalkenes or even saturated compounds, depending on the conditions. When one equivalent of Cl₂ is added to an alkyne, it typically results in the formation of a vinyl halide and a potential further reaction product.
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Regioselectivity
Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others when multiple products are possible. In the halogenation of alkynes, the position where the halogen adds can lead to different products, and understanding the regioselectivity helps predict which isomer will be favored. This concept is crucial for determining the expected products when treating alkynes with halogens.
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Related Practice
Textbook Question
For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (i) H2 , Pd/C; If you expect two products, show both.
(c)
1191
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Textbook Question
To which carbon would you expect an electrophile to add (1, 3, or 4)? Explain your answer.
1183
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Textbook Question
For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (iv) HBr (1 equiv.). If you expect two products, show both.
(c)
1087
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Textbook Question
For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (ix) Br2 (2 equiv.). If you expect two products, show both.
(c)
1010
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Textbook Question
Draw the molecular orbital picture of pent-1-en-3-yne.
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