Organic Chemistry

18.1 - Fuels and Crude oils Main Sources of electricity, also known as hydrocarbons. Formed by decomposition of plants and animals that lived millions of years ago. Hence it is finite resource 18.2 - Separation of crude oil 18.3 - Competing Uses of Different crude oil fractions

18.3.1 - Are biofuels more environmentally sustainable 19.1 - Hydrocarbon Definition: An organic compound which contain ONLY carbon and hydrogen Carbon has 4 valence electrons and can bond with many other elements. Hence it can form many types of compounds. For example:

19.1.1 - Homologous Series Definition: A family of organic compounds with the same general formula and similar chemical properties due to the presence of same functional group Properties: 1. Same general formula, 2. Mr differs by 14 from one member to another due to an extra CH 2 present Increase in carbon atoms = 3. mp and bp ↑ 4. Viscosity ↑ 5. Density ↑ 6. Solubility ↓ 7. Similar chemical properties due to the presence of same functional group 19.1.2 - Naming of organic compounds Number of carbon atoms Prefix 1 meth- 2 eth- 3 prop- 4 but- 5 pent- 6 hex- 7 hept- 8 oct- 9 non- 10 dec- Type of compound Suffix Alkane -ane Alkene -ene Alkyne -yne Alcohol -ol Carboxylic acid -oic acid

19.1.3 - Substituent group Definition: An atom or group of atoms that replaces a hydrogen atom on the main carbon chain. Substituent Formula Prefix used in naming Fluorine –F fluoro- Chlorine –Cl chloro- Bromine –Br bromo- Iodine –I iodo- Methyl –CH ₃ methyl- Ethyl –C ₂ H ₅ ethyl- 19.1.4- Alkyl groups Definition: Formed when you remove one hydrogen atom from an alkane. Alkane Alkyl group Formula Methane Methyl –CH ₃ Ethane Ethyl –C ₂ H ₅ Propane Propyl –C ₃ H ₇ Butane Butyl –C ₄ H ₉ Pentane Pentyl –C ₅ H ₁₁ Hexane Hexyl –C ₆ H ₁₃ 19.1.5 - Same substituent group appears more than once Number of same substituents Prefix 2 di- 3 tri- 4 tetra- 5 penta-

19.2 - Alkanes Definition: Saturated hydrocarbons containing only single covalent bonds between carbon atoms. ( Therefore contain maximum possible number of hydrogen atoms per carbon) General formula: C n H 2n+2 End with -ane 19.2.1 - Physical properties 1. Low mp, bp as they have simple molecular structure, so the weak intermolecular forces of attraction between the molecules need only a small amount of energy to overcome 2. As number of carbon atoms increase, mp bp,density increase, ( Molecular size increase) 3. More viscous ( Molecular size increase) 4. As number of carbon atoms increase, less flammable and produce more soot ( More carbon atoms) 5. Insoluble in water but soluble in organic solvents 19.2.2 - Chemical Reactions 1. Combustion In excess oxygen: Undergoes complete combustion: Alkane + oxygen → carbon dioxide + water In insufficient oxygen: Undergoes incomplete combustion: Alkane + insufficient oxygen → carbon monoxide + carbon + water 2. Substitution with halogens Alkane+halogen ->haloalkane+hydrogen halide ( Requires UV light) 3. Cracking Definition: Breaking down large hydrocarbon molecules into smaller, more useful hydrocarbon molecules. Require: Al 2 O 3 or SiO 2 as catalyst, 500-700 ℃ , 1atm Purpose: Produce fuel, hydrogen

19.2.3 - Isomers Definition: Compounds that have the same molecular formula but different structural formula Exp: C 4 H 10 may be butane or methylpropene 19.3 - Alkenes Definition: Unsaturated hydrocarbons containing at least one (C=C) General formula: C n H 2n End with -ene 19.3.1 - Properties 1. Low mp, bp as they have simple molecular structure, so the weak intermolecular forces of attraction between the molecules need only a small amount of energy to overcome 2. As number of carbon atoms increase, mp bp,density increase, ( Molecular size increase) 3. Insoluble in water but soluble in organic solvents 19.3.2 - Chemical Reactions 1. Combustion In excess oxygen: Undergoes complete combustion: Alkene + oxygen → carbon dioxide + water In insufficient oxygen: Undergoes incomplete combustion: Alkene + insufficient oxygen → carbon monoxide + carbon + water Compared to alkanes, higher chance of incomplete combustion and also more carbon being produced 2. Addition reaction with hydrogen ( Hydrogenation) Alkene + hydrogen → Alkane Requires Ni as catalyst, 200 ℃ , 1atm Purpose: Manufacturing of Magarine 3. Addition of steam/bromine ( Hydration/Bromination ) Alkene + steam → alcohol Conditions: Steam, H ₃ PO ₄ as catalyst, 300°C, 60–70 atm Alkene + bromine → dibromoalkane Solution turn from red-brown to colourless

4. Addition Polymerisation Definition: Many alkene monomers join together to form a long-chain polymer, without producing any other product. Requires: High pressure, high temperature, catalyst C=C bond become a C-C bond and repeats 20.1 - Alcohols Definition: Contain a hydroxyl functional group (–OH) attached to a carbon atom. Is not a hydrocarbon Formula: C n H 2n+1 OH End with -ol 20.1.1 - Properties 1. Colourless 2. Higher mp bp compared to hydrocarbon that has the same number of carbon atoms 3. Very soluble for the first few ( Due to -OH group present) 4. Mp Bp increase down the group, but solubility decreases ( Due to molecular size) 20.1.2 - Formation of Alcohols 1. Hydration ( explained in Alkene) 2. Fermentation of Glucose Glucose → ethanol + CO ₂ Requires: 40°C( No more than 40°C else enzymes would denature), Absence of oxygen Reaction is slow but renewable, Dilute solution of ethanol (15%), Requires fractional distillation for higher purity

20.1.3 - Reactions 1. Combustion Complete combustion: Alcohol + oxygen → carbon dioxide + water Burns more cleanly and completely, lesser carbon monoxide/dioxide/soot Can be easily stored as it is liquid, renewable due to fermentation of sugar from sugar cane 2. Oxidation of alcohols Alcohols can be oxidised by oxygen to form carboxylic acid Alcohol + 2[O] → Carboxylic acid + H ₂ O Test for KMnO4 -> Purple to colourless ( due to oxidation ) 3. Esterification Alcohol + Carboxylic acid ⇌ Ester + Water Require: High temperature, Concentrated sulfuric acid as catalyst 20.2 - Carboxylic acid Definition: Organic compounds containing the carboxyl functional group, –COOH. Is not a hydrocarbon Formula: C n H 2n+1 COOH End with -oic acid 20.2.1 - Properties 1. Colourless liquid ( First 4 members). Some can be coloured and in solid ( Citrus acid) 2. Form a homogeneous mixture when added with water 3. Aqueous carboxylic acid have weak pH 4-6 4. Low mp bp. Increases as it goes down the group

20.2.2 - Reactions 1. React with bases to form a carboxylate salt and water Carboxylic acid + Base → Carboxylate salt + Water 2. React with carbonates to form a carboxylate salt, carbon dioxide and water Carboxylic