Chem 102 1st EditionLecture 10Outline of Last Lecture I. Chapter 14: 3.6–3.8 : Physical Properties of Alcohols, Preparation of Alcohols, Classification of AlcoholsOutline of Current Lecture II. 3.9- Chemical Reactions of AlcoholsIII. 3.10 - Structural Characteristics of PhenolsIV. 3.11 - Nomenclature for PhenolsV. 3.12 - Physical and Chemical Properties of PhenolsVI. 3.13 - Occurrence and Uses of PhenolsCurrent Lecture3.9 - Chemical Reactions of AlcoholsCombustion • Alcohols are flammable. • The combustion products are carbon dioxide and water. Intramolecular Alcohol Dehydration • A dehydration reaction in which the components of water (-H and -OH) are removed from a single reactant • Also known as an elimination reaction • In an intramolecular alcohol dehydration, the components of water (-H and -OH) are removed from neighboring carbon atoms with the resultant introduction of a double bond into the molecule. • Dehydration of an alcohol can result in more than one alkene product, because hydrogen loss can occur from either of the neighboring carbon atoms. - Example: Dehydration of 2-butanol produces two alkenes. Zaitsev’s Rule • The major product formed in an intramolecular alcohol dehydration reaction is the alkene that has the greatest number of alkyl groups attached to the carbon atoms of the double bond.Oxidation • Addition of C-O bonds or removal of C-H bonds • Primary and Secondary Alcohols can be oxidized by mild oxidizing agents such as KMnO4, K2Cr2O7, and H2CrO4 Halogenation • Alcohols undergo halogenation reactions • In this reaction a halogen atom is substituted for the hydroxyl group producing an alkyl halide. • Alkyl halide production by this reaction is superior to alkyl halide production through halogenation of an alkane 3.10- Structural Characteristics of Phenols• Phenol: An organic compound in which an —OH group is attached to a carbon atom that is part of an aromatic carbon ring system • Aryl group: An aromatic carbon ring system from which one hydrogen atom has been removed. • General formula for an aryl alcohol: Ar-OH • Substituted phenols: Aryl group substituted with other groups like CH3, NO2 , etc. 3.11 - Nomenclature for Phenols• Phenol: Name “Phenol” is approved by IUPAC – Assign the position of the substituent followed by its name and the word phenol – Carbon atom with -OH is always number 1 and the other substituents will be assigned minimum possible numbers with reference to hydroxyl carbon 3.12- Physical and Chemical Properties of Phenols• Phenols :– Low-melting solids or oily liquids at room temperature. – Sparingly soluble in water – Many phenols have antiseptic and disinfectant properties. • The simplest phenol: phenol – A colorless solid with a medicinal odor – Melting point: 41oC – More soluble in water than any other phenolsAcidity of Phenols • Unlike alcohols, phenols are weak acids in solution. • As acids, phenols have Ka values of about 10-10 M. 3.13 Occurrence and Uses of Phenols• Phenols have antiseptic properties – 4-hexylresorcinol is an ingredient in many mouthwashes and throat lozenges. – o-phenylphenol and 2-benzyl-4-chlorophenol are the active ingredients in Lysol, a disinfectant. • Phenols have antioxidant properties: – BHA (butylated hydroxy anisole) and BHT (butylated hydroxy toluene) are used as food preservatives to protect it from air oxidation – Vitamin E is a phenolic antioxidant • A number of phenols found in plants are used as flavoring agents and/or antibacterials. – Vanillin is a phenolic which gives flavor of