[CHEM] Chapter 11.4 - Alcohols

1 DARRELL ER (COPYRIGHTED) © TOPIC 11.4: ALCOHOLS DARRELL ER (COPYRIGHTED) ©

2 CHAPTER ANALYSIS THE ABOUT MASTERY EXAM WEIGHTAGE • Important topic • Take note of alcohol’s chemical reactions • Alcohols are commonly tested • Understand how fermentation works and the conditions needed • Heavy overall weightage • Entire Organic Chemistry portion accounts for 15- 20% of each year’s Chemistry paper DARRELL ER (COPYRIGHTED) ©

3 ALCOHOLS HOMOLOGOUS SERIES FUNCTIONAL GROUP GENERAL FORMULA KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

4 Alcohols Alcohols have the general formula CnH2n+1OH and can be identified by the hydroxyl -OH functional group. Functional group Alcohols have the hydroxyl -OH functional group. Isomers Isomerism can occur in alcohols that contain at least three carbon atoms. Isomers have the same molecular formula and similar chemical properties. However, isomers have different physical properties such as different melting and boiling points and densities. DARRELL ER (COPYRIGHTED) © Name Carbon atoms Molecular Formula Full Structural Formula Condensed structural formula Methanol 1 CH3OH CH3-OH Ethanol 2 C2H5OH CH3CH2-OH Propanol 3 C3H7OH CH3CH2CH2-OH Butanol 4 C4H9OH CH3 CH2CH2CH2- OH

5 ALCOHOLS PHYSICAL PROPERTIES PRODUCTION OF ALCOHOL CHEMICAL REACTIONS KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

6 PHYSICAL PROPERTIES DARRELL ER (COPYRIGHTED) © Physical property Reasoning Melting and boiling points As the number of carbon atoms in the alcohols increases, the melting and boiling points of alcohols increases as well. As the number of carbon atoms in an alcohol increases, the size of the molecules are bigger and have stronger intermolecular forces of attraction between each other. As such, more heat energy is needed to overcome the intermolecular forces of attraction between the alcohol molecules. Hence, larger alcohol containing more carbon atoms will have higher melting and boiling points. Volatility As the number of carbon atoms in the alcohol increases, the volatility of alcohol decreases. (similar to m.p. & b.p.) With a higher relative molecular mass, there would be stronger intermolecular forces of attraction between the alcohol molecules. As such, more energy is needed to overcome the intermolecular forces of attraction between the alcohol molecules. Hence, larger alcohol molecules are less likely to evaporate in room temperature. Density As the number of carbon atoms in the alcohols increases, the density of alcohols increases. Viscosity As the number of carbon atoms in the alcohols increases, the viscosity of alcohols decreases. (more difficult to flow) Alcohols with longer hydrocarbon chains flow less easily as they tend to get stuck together. Flammability As the number of carbon atoms in the alcohols increases, the flammability of a