các loại phản ứng hữu cơ

PHẢN ỨNG HỮU CƠ PHÂN LOẠI PHẢN ỨNG HỮU CƠ loại chính: Phản ứng (Substitution) PHÂN LOẠI PHẢN ỨNG HỮU CƠ Phản ứng tách (elimination) PHÂN LOẠI PHẢN ỨNG HỮU CƠ Phản ứng cộng (addition) PHÂN LOẠI PHẢN ỨNG HỮU CƠ Phản ứng chuyển vị (rearrangement) H H C H3C C H3C CH3 C H + H H3C CH3 C H3C C CH3 PHÂN LOẠI PHẢN ỨNG HỮU CƠ PHÂN LOẠI PHẢN ỨNG HỮU CƠ DỊ LY VÀ ĐỒNG LY SỰ DỊ LY (Heterolysis) ■ Thường xảy liên kết bị phân cực ■ Cần tác nhân hỗ trợ để tách rời hai ion A A+ + B B- Heterolytic bond cleavage Ions Y + δ+ A B δ− + Y A + - B SỰ ĐỒNG LY (Homolysis) A A B + Β Homolytic bond Radicals R O O R heat alkoxyl radicals Dialkyl peroxide X X R O heat or light X Sometimes anti-addition isn’t observed Temporary participation of a neighboring group can give unusual stereochemical or regiochemical results Problem Draw mechanisms that account for the formation of each product The first step is the same in every mechanism Be sure to think about stereochemistry! Polar Reactions under Acidic Conditions Substitution at Nucleophilic C=C π Bonds 4.1 Electrophilic Aromatic Substitution Problem Draw mechanisms for the following electrophilic aromatic substitution reactions Polar Reactions under Acidic Conditions 4.1 Electrophilic Aromatic Substitution 4.2 Aromatic Substitution of Anilines via Diazonium Salts 4.3 Electrophilic Aliphatic Substitution Alkenes undergo electrophilic substitution reactions by the same addition–fragmentation mechanism as arenes Alkenylsilanes and -stannanes are good substrates for electrophilic substitution reactions: α-Substitution Example: Draw a mechanism for the following electrophilic substitution reaction: Polar Reactions under Acidic Conditions 4.3 Electrophilic Aliphatic Substitution α-Substitution is not always observed when alkenes undergo electrophilic substitution γ-Substitution is most commonly observed in the reactions of allylsilanes and stannanes Example: The Sakurai reaction The Sakurai reaction Polar Reactions under Acidic Conditions Substitution at Nucleophilic C=C π Bonds 4.1 Electrophilic Aromatic Substitution 4.2 Aromatic Substitution of Anilines via Diazonium Salts 4.3 Electrophilic Aliphatic Substitution Nucleophilic Addition to and Substitution at Electrophilic π Bonds 5.1 Heteroatom Nucleophiles 5.2 Carbon Nucleophiles Polar Reactions under Acidic Conditions Nucleophilic Addition to and Substitution at Electrophilic π Bonds 5.1 Heteroatom Nucleophiles: carbonyl compounds undergo the same types of addition and substitution reactions under acidic conditions that they under basic conditions Problem Draw mechanisms for the following carbonyl substitution reactions In the second problem, think carefully about whence the O atoms in the product come Polar Reactions under Acidic Conditions Nucleophilic Addition to and Substitution at Electrophilic π Bonds 5.1 Heteroatom Nucleophiles 5.2 Carbon Nucleophiles The carbocation that is formed upon protonation of a carbonyl compound can lose H from the α-carbon to give an enol Enols are good nucleophiles Robinson annulation Robinson annulation Robinson annulation The Mannich reaction Polar Reactions under Acidic Conditions Trimethylsilyl enol ethers, which are usually prepared by reaction of an enolate with Me3SiCl, can be used as substitutes for enols in the Lewis-acid catalyzed Mukaiyama aldol and Michael reactions