Transcript Lecture_II
Nomenclature of Alkyl Substituents If a Hydrogen is replaced by a halogen, the compound is an alkyl halide © Prentice Hall 2001 Chapter 2 1 Nomenclature of Alkyl Halides Common name - Name the alkyl group first, followed by the name of the halogen expressed as an -ide name © Prentice Hall 2001 Chapter 2 2 Nomenclature of Alkyl Halides IUPAC name - The halogen is treated as a substituent © Prentice Hall 2001 Chapter 2 3 Nomenclature of Ethers Common name Name(s) of alkyl group(s) listed first followed by the word “ether” © Prentice Hall 2001 Chapter 2 4 Nomenclature of Ethers IUPAC name - The smaller alkyl group is converted to an “alkoxy” name and used as a substituent © Prentice Hall 2001 Chapter 2 5 Nomenclature of Alkyl Substituents If a hydrogen of an alkane is replaced by an OH group, the compound is an alcohol © Prentice Hall 2001 Chapter 2 6 Nomenclature of Alcohols Alcohols are classified as primary, secondary or tertiary © Prentice Hall 2001 Chapter 2 7 Nomenclature of Alcohols Common name Name of the Alkyl group followed by the word “alcohol” © Prentice Hall 2001 Chapter 2 8 Nomenclature of Alcohols IUPAC name - The OH group is a site of reactivity (a functional group) Functional group is denoted by the suffix, “ol” CH3OH CH3CH2OH methanol ethanol © Prentice Hall 2001 Chapter 2 9 IUPAC Nomenclature of Alcohols 1. Parent Hydrocarbon is the longest continuous chain that contains the OH 2. Number the chain in direction that gives functional group the lowest number 3. If both a substituent and a functional group are present, the functional group gets the lower number © Prentice Hall 2001 Chapter 2 10 IUPAC Nomenclature of Alcohols 4. If the functional group gets the same number when counted from both directions, use direction which gives the substituent the lower number 5. If there is more than one substituent, cite substituents in alphabetical order © Prentice Hall 2001 Chapter 2 11 IUPAC Nomenclature of Alcohols System is summarized as [Substituent] [Parent Hydrocarbon] [Functional Group] © Prentice Hall 2001 Chapter 2 12 Nomenclature of Alkyl Substituents If a hydrogen is replaced by an NH2, the compound is an amine © Prentice Hall 2001 Chapter 2 13 Nomenclature of Amines Common name - Name of the Alkyl group(s) (in alphabetical order) followed by the syllable “amine” The whole name is a single word CH3NH2 methylamine © Prentice Hall 2001 CH3NCH2CH2CH3 methylpropylamine Chapter 2 14 Nomenclature of Amines IUPAC name - The NH2 group is a site of reactivity (a functional group) Functional group is denoted by the suffix, “amine” Final “e” of longest alkane group replaced by suffix “amine” CH3CH2CH2CH2NH2 1-butanamine butan-1-amine © Prentice Hall 2001 Chapter 2 15 Nomenclature of Amines Amines are classified as primary, secondary or tertiary depending on number of alkyl groups bonded to the nitrogen © Prentice Hall 2001 Chapter 2 16 Nomenclature of Amines In some compounds there are four alkyl groups bonded to a nitrogen Such compounds must be salts because it is impossible to have four bonds to nitrogen without having developed a positive charge These are quaternary ammonium salts CH3 CH3 N CH3 CH3 © Prentice Hall 2001 Cl Chapter 2 17 Structures of Alkyl Halides, Alcohols, Ethers, & Amines © Prentice Hall 2001 Chapter 2 18 Structures of Alkyl Halides, Alcohols, Ethers, & Amines © Prentice Hall 2001 Chapter 2 19 Properties of Alkyl Halides, Alcohols, Ethers, & Amines Three physical properties are compared for these classes of compounds, 1.) boiling point, 2.) melting point, and 3.) solubility Boiling point increases as the number of carbons in a hydrocarbon increases As branching increases boiling point decreases © Prentice Hall 2001 Chapter 2 20 Properties of Alkyl Halides, Alcohols, Ethers, & Amines Boiling point principally is a function of intermolecular attractions of which there are basically two kinds: 1.) dipole-dipole, and 2.) induced dipole-induce dipole Dipole-dipole interactions stronger A particularly strong dipole-dipole interaction is the hydrogen bond (requires a hydrogen atom bonded to a nitrogen, oxygen or fluorine atom) © Prentice Hall 2001 Chapter 2 21 Properties of Alkyl Halides, Alcohols, Ethers, & Amines For alkanes, there are only induced dipole-induced dipole interactions (also known as van der Waals forces or London forces) van der Waals forces are a function of surface area © Prentice Hall 2001 Chapter 2 22 Induced Dipole-Induced Dipole Interactions © Prentice Hall 2001 Chapter 2 23 Hydrogen Bonding: Strong Dipole-Dipole Interactions © Prentice Hall 2001 Chapter 2 24 Dipole-dipole Interactions Particularly important for alcohols and amines Ethers and alkyl halides have dipole moments, but their intermolecular attractions are not as strong as hydrogen bonds © Prentice Hall 2001 Chapter 2 25 Comparative Boiling Points © Prentice Hall 2001 Chapter 2 26 Melting Points Melting point are a function of: intermolecular attractions packing in the crystalline state © Prentice Hall 2001 Chapter 2 27 Solubility The more carbons that are present, the less soluble an organic compound is in water © Prentice Hall 2001 Chapter 2 28