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Organic chemistry C3 Topic 5 Making ethanol • Most ethanol is made from carbohydrates (glucose) by fermentation glucose ethanol + carbon dioxide C6H12O6 2C2H5OH + 2CO2 • The fermentation mixture is kept warm and under anaerobic conditions (no oxygen) • Yeast provides an enzyme for this reaction, breaking down glucose into ethanol and carbon dioxide Fermentation Advantages • Uses biofuels that are renewable (sugar cane and sugar beet) Disadvantages • Produces ethanol at only 15% concentration % ethanol • Different percentages of ethanol are present in different drinks Effects of alcohol • The ethanol in alcoholic drinks acts as a drug that can affect both the brain and the body • Small amounts: - less self-conscious/more confident - more talkative • - Large amounts: Slower reaction times Violent/aggressive behaviour Loss of balance/coordination Vomiting/fainting Dehydration (leading to a hangover) Increased risk of accidents Lowered inhibitions Effects of alcohol • Vitamin B deficiency causing skin damage, diarrhoea and depression • Decreased iron levels leading to anaemia • Liver damage (will no longer make toxins safe) • Destruction of brain cells • Increased risk of cancer (mouth, larynx, oesophagus, liver, stomach, colon, rectum and breast) • Increased risk of heart disease and high blood pressure • Inflammation and irritation of the intestinal and stomach lining leading to ulcers and damage to the pancreas • In men: inability to get an erection, reduced sperm count, shrinking testes and penis • In women: miscarriage and low birth weight or birth defect in babies Separating ethanol- fractional distillation • At levels of 15%, ethanol kills the yeast cells that made it, stopping fermentation • Ethanol boils at lower temperatures than water, so the fraction of the liquid that boils first will contain a higher percentage of ethanol (more concentrated) • This vapour is condensed to produce stronger drinks (spirits) Fractional distillation of ethanol Fractional distillation Advantages • Produces ethanol that is 95% pure Preparing ethanol using fractional distillation in the laboratory Making ethanol from crude oil • Ethanol can also be made by reacting ethene with steam in the presence of a catalyst • This is hydration catalyst ethene + steam → ethanol C2H4 + H2O → C2H5OH • Ethene is produced by the cracking of crude oil fractions Hydration of ethene Advantages • Product is nearly 100% pure, with little or no waste Disadvantages • Uses crude oil, which is a non-renewable resource Making ethene from ethanol • Heating ethanol to a high temperature in the presence of a suitable catalyst produces ethene and steam • This is dehydration catalyst ethanol → ethene + steam C2H5OH → C2H4 + H2O Homologous series • A series of compounds which: - have the same general formula - show a gradual variation in physical properties as exemplified by their boiling points - have similar chemical properties General formula- CnH2n+2 Alkane Formula Methane CH4 Ethane C2H6 Propane C3H8 Butane C4H10 Alkanes Chemical structure Ball-and-stick model General formula- CnH2n Alkene Formula Ethene C2H4 Propene C3H6 Alkenes Chemical structure Ball-and-stick model Alcohols • End in – ol • Contain the hydroxyl group (OH) • General formula: CnH2n+1OH Carboxylic acids • Contain a carboxyl group (-COOH) • General formula CnH2nO2 Methanoic acid- HCOOH Ethanoic acid- C2H5COOH • What would a molecule of propanoic acid look like? Oxidation of ethanol • Ethanol can be oxidised to form ethanoic acid • This reaction occurs in open bottles of wine and in the production of ethanoic acid in vinegar + ethanol oxygen + ethanoic acid water Ethanoic acid- vinegar • Vinegar is used as: - a flavouring - a preservative • Turns litmus paper and universal indicator red Ethanoic acid- vinegar Reactions of ethanoic acid acid ethanoic acid + + + acid ethanoic acid + 2CH3COOH(aq) + + + + carbonate water potassium ethanoate CH3COO-K+(aq) oxide → salt Ca2+O2-(aq) + → + → metal magnesium 2CH3COOH(aq) + salt KOH(aq) calcium oxide acid acid → potassium hydroxide CH3COOH(aq) ethanoic acid alkali → → → salt H2O(l) calcium ethanoate + water (CH3COO-)2Ca2+(aq) + H2O(l) + hydrogen salt + hydrogen magnesium ethanoate + water water → (CH3COO-)2Mg2+(aq) Mg(s) → → + + + carbon dioxide + H2(g) + water ethanoic acid + sodium carbonate → sodium ethanoate + carbon dioxide + water 2CH3COOH(aq) + Na2CO3(aq) → 2CH3COO-Na+(aq) + CO2(g) + H2O(l) Reactions of ethanoic acid acid + ethanol ethanoic acid + ethanol → ethyl ethanoate + water C2H5OH(l) → CH3COOC2H5(l) + H2O(l) CH3COOH(l) C2H4O2 + → ester + water Esters • Organic compounds that contain carbon, hydrogen and oxygen • Produced from the reaction between an organic acid and an alcohol • Used as flavourings and perfumes as they are pleasant smelling Polyesters • Used as fibres to make fabric and as plastics for making bottles • Can be recycled to form fleece that is used to make clothing Ester group Oils and fats • Esters • Oils are liquid at room temperature • Fats are solid at room temperature Making soap • Oils and fats can be broken down by boiling with concentrated alkali solution to produce soaps, which are sodium or potassium salts of long chain carboxylic acids concentrated alkali + oil/fat → soap + glycerol How does soap work? • The head is hydrophilic (water-loving: dissolves in water) • The tail (long chain of carbon atoms) is hydrophobic (water-hating: dissolves in dirt/grease) O- is an anion (hydrophilic) How does soap work? • The hydrophobic tails stick to the dirt/grease and starts to lift it off the fabric • The hydrophilic heads point towards the water and allow the dirt/grease to mix Turning oils into fats • Vegetable oils are unsaturated (contain double bonds) • Animal fats such as butter/lard are saturated (contain single bonds only) • Liquid oils can be turned into solid fats by catalytic hydrogenation. This is done by bubbling hydrogen through vegetable oils and removes the C=C unsaturation • Catalytic hydrogenation is used to manufacture margarine