NJC 8 Polymer Part 1 Student

National Junior College SH1 H1 Chemistry 1 Polymers (Part 1) – Introduction and Isomerism Learning Outcomes Students should be able to: (a) interpret, and use the nomenclature, general formulae and structural formulae (including displayed formulae) of the following classes of compounds: (i) hydrocarbons (alkanes, alkenes and benzene) (ii) halogenoalkanes (iii) alcohols (including primary, secondary and tertiary) (iv) aldehydes and ketones (v) carboxylic acids (vi) esters (vii) amines (viii) amides (b) interpret, and use the following terminology associated with organic reactions: (i) functional group (ii) addition, substitution, elimination (iii) condensation, hydrolysis (iv) oxidation and reduction [in equations for organic redox reactions, the symbols [O] and [H] are acceptable] (c) describe constitutional (structural) isomerism (d) 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] (e) deduce the possible isomers for an organic molecule of known molecular formula (f) (i) describe the shapes of the ethane, ethene and benzene molecules (ii) explain the shapes of, and bond angles, in the ethane, ethene and benzene molecules in relation to  and  carbon-carbon bonds (iii) predict the shapes of, and bond angles in, molecules analogous to those specified in (f)(ii)

National Junior College SH1 H1 Chemistry 2 1 INTRODUCTION TO ORGANIC COMPOUNDS Success Criteria: • I can classify organic compounds into aliphatic, aromatic, acyclic and cyclic compounds. • I can explain and recognise what saturated and unsaturated organic compounds are. 1.1 Classifications of Organic Compounds Saturated and unsaturated organic compounds An organic compound which contains only single bonds (C –C and C –H bonds in hydrocarbons) is said to be saturated. C CH H H H H H An organic compound which contains 1 or more double / triple bonds (C=C, C=O and C≡N bonds) is said to be unsaturated. C CH H H H

National Junior College SH1 H1 Chemistry 3 1.2 Structural Formulae of Organic Compounds Success Criteria: • I can interpret and draw different types of structural formulae (eg condensed, displayed, skeletal and stereochemical). Lactic acid has a molecular formula of C 3H6O3 and an empirical formula of CH2O. A molecular formula does not show how the various atoms in the organic compound are actually connected to one another. Hence, structural formulae are used to represent organic compounds. Below are the different structural formulae of lactic acid, CH3CH(OH)CO2H. Type of Structural Formulae Representation Characteristics Condensed CH3CH(OH)CO2H ● shows the order of arrangement of atoms ● bonds are not displayed Displayed / Full structural ● shows all atoms and bonds in the molecule Skeletal ● Carbon atoms in a straight chain are drawn in a zigzag manner ● each end of a line represents a carbon if other symbol of an atom is not written ● C–H bonds at each C are not shown. ● each C forms 4 bonds. Any “missing” bond not drawn out in a skeletal structure would be a C–H bond. Stereochemical (for optical isomers where a C has four different groups attached) CH3 H CO2H OH or CH3 H CO2H OH ● shows 3-D spatial arrangement of bonds, atoms and / or groups of atoms in a molecule ● a dashed line ( ) represents a bond into the plane of the paper ● a wedged line ( ) represents a bond out of the plane of the paper Video on Drawing Skeletal Formula. https://tinyurl.com/ skeletalformula

National Junior College SH1 H1 Chemistry 4 More examples of skeletal structures. Condensed formula CH3CH(Br)CH2CH2OH CH2=CHCH=CH2 Skeletal formula Br OH Checkpoint 1 Complete the following table. Type of formula Compound Compound Condensed HOCH2CH2OH CH3CH=CH2 Displayed / full structural Skeletal 1.3 Representation of carbon rings in formulae Cyclic rings of atoms are often represented by their skeletal formula. Name Cyclohexane Benzene Molecular Formula C6H12 C6H6 Structural Formula Skeletal Formula

National Junior College SH1 H1 Chemistry 5 1.4 Functional groups Success Criteria: • I can identify, name and draw the functional groups A functional group is made up of an atom (e.g. Cl) or a group of atoms (e.g. –OH, –CN) responsible for the characteristic chemical properties of an organic compound.

National Junior College SH1 H1 Chemistry 6 1.5 Nomenclature of Organic Compounds Success Criteria: • I can name the organic compound using IUPAC system and construct the structural formula of a compound from its IUPAC name. Naming of organic compounds is based on a systematic method developed by the International Union of Pure and Applied Chemists (IUPAC). Every IUPAC name consists of a parent (or stem), a suffix and as many prefixes as necessary. Prefix(es) Parent Suffix C OHC O CH3 Br H 2-bromopropanoic acid (a) Parent In the aliphatic unbranched chain system, the name of the parent takes its name according to the number of carbon atoms in the longest continuous chain. no. of carbon parent no. of carbon parent 1 meth- 6 hex- 2 eth- 7 hept- 3 prop- 8 oct- 4 but- 9 non- 5 pent- 10 dec- For saturated hydrocarbon, the name of the parent ends with -an-. For an unsaturated hydrocarbon with C=C bond, the name of the parent ends with -en-. In alicyclic system, the word cyclo is added to the front of the root corresponding to the same number of C atoms. cyclopentane cyclohexane Substituents Longest continuous carbon chain bearing the principal (most important) functional group Denotes principal functional group

National Junior College SH1 H1 Chemistry 7 (b) Suffix ● It indicates the principal functional group of the organic compound. ● Table 1 gives the list of the functional groups in decreasing order of priority as suffix. The functional group(s) other than principal functional groups are as prefix(es). Functional group Type of compound Suffix C OH O carboxylic acid -oic acid C O O C ester (alk)yl …-oate C N O amide -amide C H O (−CHO) aldehyde -al C C O C ketone -one C OH alcohol -ol NC amine -amine C C alkene -ene C C alkane -ane Table 1. Suffixes of various functional groups decreasing priority

National Junior College SH1 H1 Chemistry 8 (c) Prefix ● Once the principal functional group is identified, a ny other functional group in the compound is treated as a substituent on the parent chain, and is named by a prefix. ● A substituent group is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon. Substituent group Prefix Substituent group Prefix –F fluoro- Alkyl group CH3− CH3CH2− CH3CH2CH2− methyl- ethyl- propyl- –Cl chloro- –Br bromo- –I iodo- –OH hydroxy- Aryl group or C6H5– phenyl- –NH2 amino- Table 2. Common prefixes Arabic numerals (1,2,3) are used to indicate the positions of attachment of substituents, C=C bonds and certain principal functional groups. They are known as positional numbers. 3-methyl-3-phenylpentane For carbon chain with 3 carbon or more, we need to specify the position of the principal functional group. The position of the double b ond is denoted using the smaller carbon number. E.g. But-2-ene shows that the C=C is from C2 to C3 CH3CH2CH=CH2 But-1-en