JPJC 2026 Intro to Organic Chemistry and Isomerism Lecture Notes

2026 JPJC JC1 H2 Chemistry (9476) 1 Topic 8: Introduction to Organic Chemistry and Isomerism Jurong Pioneer Junior College 2026 JC1 H2 Chemistry (9476) Organic Chemistry Topic 8: Introduction to Organic Chemistry and Isomerism Assessment Objectives (for Introduction to Organic Chemistry) Candidates should be able to: (a) interpret, and use the nomenclature, general formulae and displayed formulae of the following classes of compound: (i) hydrocarbons (alkanes, alkenes and arenes) (ii) halogen derivatives (halogenoalkanes and halogenoarenes) (iii) hydroxyl compounds (alcohols and phenols) (iv) carbonyl compounds (aldehydes and ketones) (v) carboxylic acids and derivatives (acyl chlorides and esters) (vi) nitrogen compounds (amines, amides, amino acids and nitriles) (b) interpret, and use the following terminology associated with organic reactions: (i) functional group *(ii) degree of substitution: primary, secondary, tertiary, quaternary (iii) homolytic and heterolytic fission (iv) carbocation (v) free radical (vi) electrophile (Lewis acid), nucleophile (Lewis base) (vii) addition, substitution, elimination, condensation, hydrolysis (viii) oxidation and reduction (in equations for organic redox reactions, the symbols [O] and [H] are acceptable) *(c) Interpret, and use the following terminology associated with organic reactivities: (i) delocalisation (ii) electronic effect (electron–donating and electron–withdrawing effect) (iii) steric effect (steric hindrance) (d) describe sp 3 hybridisation, as in ethane molecule, sp 2 hybridisation, as in ethene and benzene molecules, and sp hybridisation, as in ethyne molecule (e) explain the shapes of, and bond angles in, the ethane, ethene, benzene, and ethyne molecules in relation to  and  carbon–carbon bonds (f) predict the shapes of & bond angles in, molecules analogous to those specified in (e) (g) apply (b) & (c) to the understanding of mechanisms in terms of organic structure & bonding (h) recognise that the mechanisms of polar reactions involve the flow of electrons from electron-rich to electron-poor sites Assessment Objectives (for Isomerism) (i) describe constitutional (structural) isomerism (j) describe cis-trans isomerism in alkenes, and explain its origin in terms of restricted rotation due to the presence of –bonds (use of E, Z nomenclature is not required) (k) explain what is meant by a chiral centre (l) deduce whether a given molecule is chiral based on the presence or absence of chiral centres and/or a plane of symmetry (m) recognise that an optically active sample rotates plane-polarised light and contains chiral molecules. (n) recognise that enantiomers have identical physical properties except in the direction in which they rotate plane–polarised light (usage of the term diastereomers is not required) (o) recognise that enantiomers have identical chemical properties except in their interactions with another chiral molecule (p) recognise that different stereoisomers exhibit different biological properties, for example in drug action (q) deduce the possible isomers for an organic molecule of known molecular formula (r) identify chiral centres and/or cis-trans isomerism in a molecule of given structural formula * These learning outcomes (LOs) will be covered in later topics.

2026 JPJC JC1 H2 Chemistry (9476) 2 Topic 8: Introduction to Organic Chemistry and Isomerism Section Content LOs Page 1 History and Importance of Organic Chemistry − 3−4 2 Formulae of Organic Compounds (a) 5−6 3 Functional Groups and Homologous Series (a), (b)(i) 7−9 4 Naming of Organic Compounds (IUPAC) (a), (b)(i) 9 4.1 Stem 10 4.2 Stem–suffix 10 4.3 Suffix 10 4.4 Prefix 10 4.5 Converting name to structure 10−11 4.6 Converting structure to name 11−12 5 Isomerism 5.1 Overview of isomerism (i) 13 5.2 Cis–trans isomerism (j), (q), (r) 14-15 5.3 Enantiomerism (k)−(o), (q), (r) 16−18 5.4 Importance of stereoisomerism in biological system (p) 19 6 Reactions of Organic Compounds (g), (h) 6.1 Types of Reagents (b) 20 6.2 Types of Reactions (b) 21−22 6.3 Breaking Covalent Bonds (b) 22−23 6.4 Understanding Reaction Mechanism (g), (h) 24 7 Hybridisation of Orbitals 7.1 Occurrence of hybridisation (d) 25 7.2 Type of hybridisation (d), (e), (f) 26−29 7.3 Effect of hybridisation on covalent bonds (d) 30 8 Annex A : Hybridisation in Other Atoms 31 – 32 Recommended References: 1. Understanding Chemistry – Basic Organic Chemistry URL : http://www.chemguide.co.uk/mechmenu.html#top 2. Understanding Chemistry for Advanced Level (3rd Edn) by T. Lister & J. Renshaw 3. Fundamentals of Organic Chemistry (4th Edition) by J. McMurry 4. Organic Chemistry (4th Edition) by T.M. Leung & C.C. Lee 5. Organic Chemistry I, Translating the Basic Concepts (2nd Edn) by David R. Klein 6. A Level Chemistry (4th Edn) by E. N. Ramsden 7. Chemistry for Advanced Level by P. Canns, P. Hughes 8. Chemistry in Context (5th Edn) by G. Hill, J. Holman

2026 JPJC JC1 H2 Chemistry (9476) 3 Topic 8: Introduction to Organic Chemistry and Isomerism 1 HISTORY AND IMPORTANCE OF ORGANIC CHEMISTRY 1.1 WHAT IS ORGANIC CHEMISTRY Organic chemistry is the study of the structure, properties, composition, reactions and preparation of carbon−containing compounds (excluding carbonates & oxides of carbon). Carbon, with an electronic configuration of 1s2 2s2 2p2, has 4 valence electrons and is able to form single, double and triple strong covalent bonds with other atoms such as H, O, N, S and halogens. Carbon is also unique among the elements in its ability to self −link into chains or rings (i.e. known as catenation) of almost infinite size, giving rise to the millions of organic compounds known. 1.2 HISTORY OF ORGANIC CHEMISTRY

2026 JPJC JC1 H2 Chemistry (9476) 4 Topic 8: Introduction to Organic Chemistry and Isomerism 1.3 IMPORTANCE OF ORGANIC CHEMISTRY Organic chemistry deals with the chemistry of life and natural carbon compounds as well as the huge number of synthetic carbon compounds. At the end of the last century, the number of these carbon compounds amounted to 15 million with an estimated annual increase of about 600,000 compounds. We are living in a world which is largely shaped by organic compounds, e.g.: • the commodities we use (wood, plastics, wool, leather); • the sources of primary energy (petroleum, natural gas, coal); • the remedies for illnesses (medicine, herbs). But organic compounds can also put our lives at risk, e.g.: • the insecticide DDT (dichlorodiphenyltrichloroethane) accumulates in the food chain and causes ecological damage; • the chlorofluorocarbons (CFCs) used as propellants in spray cans, which damage the protective ozone layer of the atmosphere. The knowledge and control of organic chemistry is constantly improving, so that it can be applied usefully to men and nature.

2026 JPJC JC1 H2 Chemistry (9476) 5 Topic 8: Introduction to Organic Chemistry and Isomerism 2 FORMULAE OF ORGANIC COMPOUNDS To do well in organic chemistry, you must first learn to interpret the drawings/ representations ( i.e. formulae) that organic chemists use. When you see a representation of a molecule, it is absolutely critical that you can read all of the information contained in that drawing. Only with this skill, can you master reactions and concepts easily. For stereochemical formula, represents a bond pointing out of the plane of the paper, represents a bond pointing into the plane of the paper and represents a bond lying on the plane of the paper. (See Section 5.3.2)

2026 JPJC JC1 H2 Chemistry (9476) 6 Topic 8: Introduction to Organic Chemistry and Isomerism 2.1 DRAWING SKELETAL FORMULA