TJC 2025 Alcohols Notes (Student)

1 ©TJC IP Chemistry Temasek Junior College Integrated Programme Year 4 Chemistry Topic 10.4: Alcohol Notes Name: Class: Date: Learning objectives At the end of this notes, you must be able to: (a) describe alcohols as a homologous series containing the –OH group (b) draw the structures of branched and unbranched alcohols C1–C4 and name the unbranched alcohols methanol to butanol (c) describe the reactions of alcohols in terms of combustion , acid -metal displacement and oxidation to carboxylic acids (d) describe the formation of ethanol by the catalysed addition of steam to ethene and by fermentation of glucose Topic Outline 1 Introduction 1.1 Nomenclature 2 Physical Properties of Alcohols 2.1 Melting and Boiling points 3 Isomerism in Alcohols 4 Chemical Properties of Alcohols: Reaction of alcohols 4.1 Combustion 4.2 Acid-Metal displacement 4.3 Oxidation 4.4 Condensation 5 Manufacturing Ethanol from Ethene 5.1 Addition of Steam (Hydration) 5.2 Fermentation of Yeast 6 Use of Ethanol as a Biofuel

2 ©TJC IP Chemistry 1 Introduction • Alcohols are organic compounds made up of carbon, hydrogen and oxygen. • General Formula : CnH2n+1 OH or ROH • Functional Group : –OH 1.1 Nomenclature • Alcohol is named with a suffix ‘–ol’ to indicate presence of the alcohol group. • The following table shows the first four members of the alcohol homologous series. Structural formula Displayed / Full structural formula and Name General formula of alcohols, in terms of n, where n is an integer starting with n = 1 CH3OH methanol CH3CH2OH ethanol CH3CH2CH2OH propan-1-ol CH3CH2CH2CH2OH butan-1-ol ____________ functional group H H H C H C H H H C H H C O H H H H C H H C H H C O H H H H C H H C O H H H H C O H

3 ©TJC IP Chemistry 2 Physical Properties of Alcohols • Alcohol molecules have an alkyl group as well as a –OH group. • In addition to intermolecular forces of attraction, hydrogen bonds between the molecules are present as well. • The hydrogen bond between alcohol molecules refers to the electrostatic forces of attraction between a hydrogen atom that is covalently bonded to the oxygen atom (an electronegative atom) and a lone pair of electrons on an oxygen atom from another alcohol molecule. Example: Ethanol CH3 – CH2 – OH 2.1 Boiling Point and Melting Point (i) Boiling points of alcohols are higher than hydrocarbons of similar Mr. Boiling points of alcohols are much higher than hydrocarbons of similar Mr. Reason: This is due to the –OH group which allows for hydrogen bonding between alcohol molecules. Hydrogen bonding between alcohol molecules: Compound Mr Boiling Point / °C CH3CH2OH