Textbook Question
Imagine an electrophilic addition where the first step is exothermic. Which carbocation—2°, 3°, or neither—would you expect to form preferentially? Explain.
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Ch. 8 - Alkenes I: Properties and Electrophilic Additions
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
Chapter 7, Problem 28
For the enzyme isopentenyl pyrophosphate isomerase, IPP binds tightly as a result of interactions between the active site amino acid residues and the diphosphate of IPP. Without concerning yourself with the structure of amino acids, what charges might you expect to be present in the active site to hold IPP in place so that the enzymatic reactions can occur?
Verified step by step guidance1
Understand the structure of isopentenyl pyrophosphate (IPP), which contains a diphosphate group. This group is negatively charged due to the presence of phosphate ions.
Consider the nature of enzyme-substrate interactions. Enzymes often use electrostatic interactions to stabilize substrate binding. Therefore, positively charged residues in the active site are likely to interact with the negatively charged diphosphate group of IPP.
Identify common positively charged amino acid residues that might be present in the active site. These include lysine (Lys) and arginine (Arg), which have positively charged side chains at physiological pH.
Recognize that the active site may also contain other polar or charged residues that can form hydrogen bonds or ionic interactions with the diphosphate group, further stabilizing IPP binding.
Consider the overall environment of the active site, which may be optimized to enhance the binding affinity through a combination of electrostatic interactions, hydrogen bonding, and van der Waals forces, ensuring that IPP is held securely for the enzymatic reaction to proceed.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Enzyme Active Site
The active site of an enzyme is the region where substrate molecules bind and undergo a chemical reaction. It is typically a pocket or groove on the enzyme's surface, formed by specific amino acid residues that create a unique chemical environment. This environment facilitates the binding of substrates and stabilizes transition states, enhancing the rate of the reaction.
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Charge Interactions
Charge interactions are crucial for substrate binding in enzyme active sites. These interactions can include ionic bonds, where oppositely charged groups attract each other, and hydrogen bonds, which involve a hydrogen atom shared between electronegative atoms. In the case of IPP, the diphosphate group likely interacts with positively charged residues in the active site, stabilizing its binding and positioning for catalysis.
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Diphosphate Group
A diphosphate group consists of two phosphate units linked together, carrying a negative charge due to the presence of oxygen atoms bonded to phosphorus. In biochemical contexts, such as enzyme-substrate interactions, the negative charge of diphosphate groups can form electrostatic interactions with positively charged amino acid residues, aiding in substrate stabilization and proper orientation for enzymatic activity.
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Related Practice
Textbook Question
What is the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HCl?
(e)
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Textbook Question
Which is the most likely transition state for the reactions shown? Explain your answer. [Note the difference in the size of the partial charges or partial unpaired electrons.]
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Textbook Question
What is the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HCl?
(d)
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Textbook Question
Which would you expect to be more selective for carbocation formation, the electrophilic addition of HF or HBr to 2-methylbut-2-ene? Explain your answer.
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Textbook Question
Draw a mechanism for the acid-catalyzed conversion of DPP to IPP. How do you know that your mechanism is correct?
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