TAILIEUCHUNG - Lecture Organic chemistry - Chapter 22: What does the benzene ring do to its substituents?

Chapter 22 - What does the benzene ring do to its substituents? After attending lectures, reading the text and working assigned problems related to this chapter, students will have acquired the following knowledge and abilities: Given the IUPAC name of a phenol derivative, be able to draw its structure; know how resonance influences the stability of benzylic cations, anions, and radicals as compared to similar non-benzylic species; be able to apply a benzyl ether as a protecting group in multi-step synthesis; given a series of phenols, be able to rank their relative acidity. | Chapter 22: What does the benzene ring do to its substituents? Benzylic resonance for +/./- All stabilized by the overlapping p orbitals Benzylic radicals are reactive intermediates in the α-halogenation of alkylbenzenes Therefore: Benzylic halogenation No EAS (Which needs FeBr3) Mechanism of benzylic halogenation Substitution occurs only at the benzylic position: Attack on the benzene destroys aromaticity! The two propagation steps Benzylic cation (SN1 reaction) Mechanism: Octet! Needs e-pushers; parent is too slow SN2 is accelerated Transition state is delocalized SN sp2 Benzylic Acidity: Resonance in Benzylic Anions Compare CH2=CH-CH3 pKa ~ 40 Benzylic Oxidation-Reduction or Na2Cr2O7, H+ C-C bond broken via: Can be stopped here (Recall electrophilic aromatic substitution: alkyl acyl) Neutral, mild Protecting group Discarded Deprotected Untouched Benzylic hydrogenolysis: Unique! Compare tert-Bu ethers as protecting groups, need acid for deprotection Compare allylic oxidation wth .

• Hoá học
• Organic chemistry
• Lecture Organic chemistry
• Hóa học hữu cơ
• Bài giảng Hóa học hữu cơ
• Benzene substituents
• Benzylic halogenation
• In this workbook
• experiments are elaborated using small scale glassware and equipments from a Small Lab Kit
• developed at the Department of Chemistry
• Faculty of Science
• Chulalongkorn University in Thailand
• This Small Lab Kit was created as a result of the research project entitled “Chemistry Laboratory Based on Chemical Safety and Pollution Minimization” sponsored by Thai Research Fund (RDG 3 07 2543)
• One of the outcomes of this project is the organic laboratory book entitled “Organic Chemistry Laboratory Based on Chemical Safety and Pollution Minimization” written in Thai by professors from 7 universities in this project
• They compiled
• adjusted and tested the experiments taken from several traditional organic chemistry laboratory books using the prototype of Small Lab Kit
• Currently
• some selected experiments from this Thai organic chemistry laboratory text have further been modified
• rewritten and edited in English as appeared in this workbook
• Some experiments ar
• Ebook Organic chemistry
• Nucleophilic substitution
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• Principles of organic chemistry
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