NJC 17A Alcohol (Student)_2026

National Junior College SH2 H2 Chemistry 1 7 HYDROXY COMPOUNDS

National Junior College SH2 H2 Chemistry 2 7A: Alcohols 7A.1 INTRODUCTION • Alcohols are organic compounds containing hydroxyl functional group (−OH). • General chemical formula of an aliphatic alcohol is CnH2n+1OH. • Aliphatic alcohols are also often represented as “R-OH” where R = alkyl groups. 7A.2 CLASSIFICATION AND NOMENCLATURE OF ALIPHATIC ALCOHOLS 7A.2.1 Classification There are 3 classes of aliphatic alcohols - differ in the no. of alkyl groups on the C atom to which –OH is attached. Type of Alcohol No. of alkyl groups on C atom to which –OH is attached to Primary (1°) 1 Secondary (2°) 2 Tertiary (3°) 3 Checkpoint 1 Classify each of the following aliphatic alcohols as a primary, secondary or tertiary alcohol. ___________________ __________________ ___________________ ___________________ ___________________ ___________________ R C OH H H R C OH R'' R' R C OH H R'

National Junior College SH2 H2 Chemistry 3 7A.2.2 Nomenclature • Alcohols are named by replacing the terminal ‘ -e’ of the corresponding alkane by ‘-ol’. • The parent chain must be the longest chain containing the –OH group. • The carbon with the –OH attached is given the lowest number possible. • Substituents are numbered according to their position on the parent chain, and listed in alphabetical order. • If more than one –OH group is present, the terms, di and tri are used, together with their respective numbers. Checkpoint 2 Fill in the correct structural formula of the alcohol. (a) (b) (c) Propane-1,3-diol 2-methylpropan-2-ol 2-ethylcyclohexanol Negative effects of excessive alcohol consumption (FYI) In Singapore, binge drinking (defined as having four or more alcoholic drinks in one session for women, and five or more for men) is most common among 18- to 29-year-olds: 18.7% of men and 12.2% of women. In 2010, the Singapore Mental Health Study found that about 3.5% of our citizens suffered from alcohol abuse at some point in their lives and 0.5% from alcohol addiction (or alcoholism).1 Alcohol is eliminated from the body by various metabolic mechanisms. In general, alcohol metabolism is achieved by both oxidative and non-oxidative pathways. A person’s brain develops until the age of about 24. During this time, alcohol abuse can result in learning difficulties and social problems. Alcohol is also a known cause of cancers of the mouth, throat (pharynx), voice box (larynx), oesophagus, liver, co lon and rectum, and breast. 3 Alcohol may increase the risk of cancer of the pancreas too. For each of these cancers, the risk increases with the amount of alcohol consumed. The exact way alcohol affects cancer risk isn’t completely understood. In fact, there might be several different ways it can raise risk, and this might depend on the type of cancer. 1 He