Chem 102 1st Edition Lecture 9 Outline of Last Lecture I. Chapter 14: 3.1 – 3.5 : Bonding characteristics of Oxygen Atoms in Organic Compounds, Structural Characteristics of Alcohols, Nomenclature of Alcohols, Isomerism for Alcohols,Important Commonly Encountered AlcoholsOutline of Current Lecture II. 3.6 - Physical Properties of AlcoholsIII. 3.7 - Preparation of AlcoholsIV. 3.8 - Classification of AlcoholsCurrent Lecture3.6 - Physical Properties of Alcohols• Alcohol molecules have both polar and nonpolar character. – The hydroxyl group is polar part of the molecule – The alkyl (R) group is nonpolar part of the molecule • The physical properties depend on which portion of the structure “dominates.” – Length of the nonpolar carbon chain – Number of polar hydroxyl groups Boiling Points and Water Solubilities • The boiling points of 1-alcohols with an —OH group on an end carbon increases as the length of the carbon chain increases. • Small monohydroxy alcohols are soluble in water in all proportions. • As carbon chain length increases beyond three carbons, solubility in water rapidly decreases Alcohols and Hydrogen Bonding • The differences in physical properties between alcohols and alkanes 1. Alcohols have higher boiling points than alkanes of similar molecular mass. 2. Alcohols have much higher solubility in water than alkanes of similar molecular mass. • These differences are due to the participation of –OH group in hydrogen bonding. 3.7 - Preparation of Alcohols• Prepared by hydration of alkenes • Alkenes react with water (an unsymmetrical addition agent) in the presence of sulfuric acid (the catalyst) to form an alcohol • Markovnikov’s rule is used to determine the predominant alcohol product 3.8 - Classification of Alcohols• Alcohols are classified as primary (1o), secondary (2o), or tertiary (3o) alcohols • Primary alcohol (1o): Hydroxyl-bearing carbon atom is bonded to only one other carbon atom. • Secondary alcohol (2o): Hydroxyl bearing carbon atom is bonded to two other carbon atoms. • Tertiary alcohol (3o): Hydroxyl-bearing carbon atom is bonded to three other carbon atoms. • Reactions are dependent on the type of
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