2025 NYJC H2 Chem Hydroxy Compounds Lecture Notes 1.pdf

1 Nanyang Junior College Chemistry (9729) Lecture Notes 14 Hydroxy Compounds Lecturer: Mrs Judy Tan JC2/2025 Content  Alcohols (exemplified by ethanol) (i) formation of halogenoalkanes (ii) reaction with sodium; oxidation; dehydration (iii) the tri-iodomethane test  Phenol (i) its acidity; reaction with bases and sodium (ii) nitration of, and bromination of, the aromatic ring Learning Outcomes Candidates should be able to: (a) recall the chemistry of alcohols, exemplified by ethanol: (i) combustion (ii) nucleophilic substitution to give halogenoalkanes (iii) reaction with sodium (iv) oxidation to carbonyl compounds and carboxylic acids (v) dehydration to alkenes (b) suggest characteristic distinguishing reactions for the different classes of alcohols (primary, secondary and tertiary alcohols), e.g. mild oxidation (c) deduce the presence of a CH 3CH(OH)– group in an alcohol from its reaction with alkaline aqueous iodine to form tri-iodomethane (d) recall the chemistry of phenol, as exemplified by the following reactions: (i) with bases (ii) with sodium (iii) nitration of, and bromination of, the benzene ring (e) explain the relative acidities of water, phenol and ethanol in aqueous medium (interpret as Brønsted-Lowry acids) Textbooks and References 1. Chemistry for advanced level; Peter Cann, Peter Hughes, John Murray (Publishers) Ltd Page 477- 493 2. Chemistry in Focus; John Andrew, Paul Rispoli; 2 nd edition Hodder & Stoughton Page 276-299 3. Organic Chemistry; John McMurry; 5th edition Brooks/Cole

2 1. INTRODUCTION  Hydroxy compounds contain the –OH functional group.  They can be classified as aliphatic compounds called alcohols or aromatic compounds, phenols. Tertiary alcohols 3 R groups Primary alcohols 1 R group Alcohols –OH group is bonded to an alkyl group General formula is C H OH Phenols –OH group is directly bonded to an aryl group OH OH CH3 Secondary alcohols 2 R groups R C H R OH H C H R OH R C R R OH Hydroxy compounds Note: “R” represents alkyl or aryl groups.

3 2. ALCOHOLS  General formula for alcohols: CnH2n+1OH or CnH2n+2O where n = 1, 2, 3, …  All alcohols (except methanol) are constitutional isomers (functional group isomers) of ethers. Ethers (C–O–C), have the same general formula as alcohols but its reactions are not required in the H2 syllabus. 2.1 Nomenclature and Classification of Alcohols  Alcohols have names ending with –ol e.g. Methanol, Ethanol, Propanol  Examples: IUPAC Name Molecular Formula Structural Formula Displayed formula (Full Structural Formula) Classification propan-1-ol C3H7OH CH3CH2CH2OH C CC H H H H O H H H H primary propan-2-ol C3H7OH CH3CH(OH)CH3 C CH H H H O C H H H H secondary 2-methylpropan-2-ol C4H9OH (CH3)3COH C C C C O H H H H H H H H H H tertiary cyclopentanol C5H9OH OH C C C C C O H H H H H H H H H H seconda