교과서 질문
Why are NH3 and CH3NH2 no longer nucleophiles when they are protonated?
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Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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TOC.tableOfContents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding31
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds: Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
모든 교과서
Bruice 8th EditionCh. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds문제 3
Bruice 8th EditionCh. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds문제 310장, 문제 3
Explain the difference in reactivity between CH3O+H2 and CH3OH in a nucleophilic substitution reaction. (The pKa of H3O+ is −1.7.)
검증된 단계별 안내1
Step 1: Understand the nature of the species involved. CH3O+H2 is a protonated methanol molecule, where the oxygen atom carries a positive charge due to the addition of a proton (H+). CH3OH, on the other hand, is neutral methanol, where the oxygen atom has lone pairs of electrons and no formal charge.
Step 2: Analyze the stability of the species. The protonated methanol (CH3O+H2) is less stable because the positive charge on the oxygen atom creates significant electron deficiency. This makes it more reactive compared to neutral methanol (CH3OH), which is more stable due to the absence of a formal charge.
Step 3: Consider the leaving group ability. In a nucleophilic substitution reaction, the leaving group plays a critical role. When CH3O+H2 reacts, it can lose a water molecule (H2O) as the leaving group. Water is a very good leaving group because it is neutral and stable. In contrast, CH3OH does not have a good leaving group unless it is first protonated to form CH3O+H2.
Step 4: Relate the pKa values to reactivity. The pKa of H3O+ is −1.7, indicating that it is a very strong acid. This means that the conjugate base (H2O) is very stable. The protonation of CH3OH to form CH3O+H2 increases the reactivity of the molecule in a nucleophilic substitution reaction because it facilitates the formation of a stable leaving group (H2O).
Step 5: Conclude the difference in reactivity. CH3O+H2 is more reactive in a nucleophilic substitution reaction compared to CH3OH because the protonation of CH3OH enhances the leaving group ability by forming water (H2O), a stable and neutral molecule. Neutral CH3OH lacks this enhanced leaving group ability unless it is first protonated.
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주요 개념
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Nucleophilic Substitution Reactions
Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile. The nucleophile donates a pair of electrons to form a new bond, while the leaving group departs with its electrons. Understanding the mechanism (either SN1 or SN2) is crucial, as it influences the reactivity and the rate of the reaction based on sterics and the nature of the nucleophile.
추천 영상:
01:47
Nucleophiles and Electrophiles can react in Substitution Reactions.
Acidity and pKa
The pKa value indicates the strength of an acid; lower pKa values correspond to stronger acids. In this context, H3O+ (with a pKa of -1.7) is a very strong acid, which means it can readily donate protons. The acidity of a compound affects its reactivity in nucleophilic substitution, as stronger acids can stabilize the transition state and influence the nucleophile's ability to attack.
추천 영상:
07:45Identifying pKa values
Stability of Carbocations
Carbocations are positively charged carbon species that play a key role in many nucleophilic substitution reactions, particularly in the SN1 mechanism. The stability of a carbocation is influenced by factors such as the degree of substitution (tertiary > secondary > primary) and resonance. A more stable carbocation will form more readily, affecting the overall reactivity of the substrate in the reaction.
추천 영상:
05:58Determining Carbocation Stability