85 21 Important Concepts itroge 21 Important Concepts 21 Important Concepts 6 7. kSrOgaaYs832 9 ish between primary and rized by iminium ion 88 When irradiated or exposed to catalytic amounts of copper, diazomethane evolves N2 to generate the reactive carbene methylene, :CH2. Methylene reacts with alkenes by addition to form cyclopropanes, stereospecifically. 21 Important Concepts 1. Amines – Derivatives of ammonia 2. Chemical Abstracts – names amines as alkanamines and benzenamines, alkyl substituents on nitrogen are designated as N-alkyl. • A second naming system is based on the label aminoalkane. • Common names are based on the label alkylamine. 3. Nitrogen Hybridization in Amines – sp3 • Non-bonding pair of electrons functions as a substituent. The tetrahedral arrangement inverts rapidly through a planar transition state. 21 Important Concepts 4. Lone Electron Pair – held less tightly than in alcohols and ethers (nitrogen is less electronegative). Amines have less hydrogen bonding capability, higher basicity and nucleophilicity and lower acidity. 5. Spectroscopy – • IR – helps to distinguish between primary and secondary amines • NMR – indicates presence of nitrogen-bound hydrogens. Both hydrogen and carbon are deshielded by the neighboring nitrogen. • Mass Spectra – characterized by iminium ion fragments 21 Important Concepts 6. Synthesis of Amines – indirect methods (displacement with azide or cyanide, reductive amination) are superior to direct alkylation of ammonia. 7. -NR3 Group – in a quaternary amine is a good leaving group in E2 reactions. (Basis of Hofmann elimination.) 8. Nucleophilic Reactivity – Amines react with electrophilic carbon (haloalkanes, aldehydes, ketones and carboxylic acids and their derivatives)