Presentation on theme: "Acids, Esters and Fats Alkanoic Acids (Carboxylic Acids),"— Presentation transcript:
1 Acids, Esters and Fats Alkanoic Acids (Carboxylic Acids), Esters, Fats, Oils and soaps
2 Index Alkanoic Acids CnH2n+1COOH Ethanoic acid Esters Fats and oils Fatty acids and soap
3 Alkanoic Acids CnH2n+1COOH PropertiesBecause of the ability of lower molecular alkanoic acids to form hydrogen bonds, they are soluble in water. They have high b.p.’s for the same reason. They also have a sharp smell. Human sweat contains a mixture of these compounds.RCOH-+Alkanoic acids are weak acids, so can react with some metals andalkalis.2 CH3COOH + Mg (CH3COO)2Mg + H2CH3COOH + NaOH CH3COONa + H2OMagnesium ethanoateSodium ethanoateCH3COOH + K2CO 2 CH3COOK + H2O + CO2
4 Carboxylic acid (alkanoic acid) HCH3O - HONamingCarboxylicacidsCarboxylic acid (alkanoic acid)1. Decide on the type of compound (ie. consider functional group)2. Select the longest chain5 C’s pentanoic acid3. Name the compound with the branched chains in ascending order.3-methylpentanoic acid
5 Ethanoic Acid, CH3COOH Manufacture C2H5OH + O CH3COOH + H2O oxidationC2H5OH O CH3COOH H2OEthanol can produced by fermentation, further oxidationproduces ethanoic acid. Vinegar is 4-5% ethanoic acid.Ethanoic acid can be artificially produced byFrom ethene (by hydration)From naphtha (by oxidation)
6 ESTERS Esterification Alcohol + Carboxylic Acid Ester + Water Esters have sweet smells and are more volatile than carboxylic acidsThey are responsible for sweet fruit smells. 280 aromas make up astrawberry smell!!3-methylbutyl ethanoate in bananas.2-aminobenzoate is found in grapes.We imitate these smells by manufacturing flavourings.Esters are also used in perfumes.Esters can also be used in glues.Polyesters are used to make plasticisers.Methyl ester is a biodiesel.
7 Naming Esters R-OH + R-COOH R-COOR + Water ethyl propanoate R-yl R-oateFirst, the 1st word comes from thealcohol. The name ends in –yl.Second,find the C=O in the carboxylategroup, this gives the 2nd word with theending –oate. This comes from the acid.C2H5COCH3 CH2 COO CH3 CH2ethyl propanoate
8 Ester formation Condensation Reaction + + CH3OH CH3COOH + Ester linkHO++RHORCOHCH3OHCH3COOH +CH3COOCH H20methyl ethanoateThe reaction is brought about by heating a mixture of carboxylic acidand alcohol with a little concentrated sulphuric acid, which acts as acatalyst, as well as absorbing the water produced.
9 Hydrolysing Esters Alcohol + Carboxylic Acid Ester + Water CondensationAlcohol Carboxylic Acid Ester + WaterHydrolysisAlcohol Carboxylic Acid Ester + WaterThe ester is split up by the chemical action of water, hydrolysis.RCOH+Bonds brokenEster + Water+RCOHBonds formedCarboxylic Acid + Alcohol
10 Fats and oils50% of yourbrain is fat.All living things need fats(solids) and oils(liquids). They tend to beinsoluble in water.Fats and oils are a range of substances all based on glycerol,propane-1,2,3-triol.Natural fats and oils are a mixture of triglyceride compounds.Each OH group can combine chemically with one carboxylic acidmolecule, the resulting molecules are fats and oils.They are described as triglycerides.The hydrocarbon chain in each can be from 4 to 24 C’s long.The C’s can be single bonded (saturated) or double bonded(unsaturated).The latter causes the hydrocarbon chains to kink and so makingit harder for the molecules to pack as close together,making their m.p.’s lower. (weakens the intermolecular forces)Glycerolpropane-1,2,3-triol
11 Omega 3 fattyacids make up alarge % of yourbrain’s fatFats and oilsThe degree of saturation in a fat or oil can be determined by theIodine number. (bromine can also be used).The iodine reacts with the C=C bonds, so the greater the numberthe greater the number of double bonds.As you can see the solid fats – butter, beef fat & lard have low iodine nos as they are more saturated than the unsaturated oils.FatAv Iodine NoButter40Beef Fat45Lard50Olive Oil80Peanut Oil100Soya Bean Oil180Margarine is made from vegetable oils, butterfrom animal fats. One reason why margarinespreads better!
12 Fats in the diet Fats provide more energy per gram than carbohydrates. Fat molecules are insoluble, and tend to group together and forma large droplet. This is how fat is stored in the adipose tissue.We store our extra energy as fat.The type of fat we eat is important, animal fats contain important fatsoluble vitamins. Oils are thought to be healthier than solid fats asthey are less likely to be deposited inside our arteries.However, there is an ongoing debate about which fats are better for us.Polyunsaturated fats are considered to be less potentially harmful to theheart.
13 Structures of fats and oils Hydrolysis of a fat or oil produces glycerol (alcohol) and 3 carboxylicacids. The carboxylic acids are usually called fatty acids. Most fats andoils are, in fact, esters of propane-1,2,3-triol, sometimes called, triesters.R 1, 2, 3 are along carbon chains,which can be the same or differentHydrolysisFatty Acids + GlycerolTriesters.GlycerolpartFatty acid part
14 Fatty Acids Us Hydrogenation C17H35COOH CH3(CH2)16COOH Stearic Acid (Suet, animal fat) SaturatedC17H33COOHCH3(CH2)7CH=CH(CH2)7COOHOleic Acid (olive oil) UnsaturatedOctadec-9-enoic acidHydrogenationUsThe addition of hydrogen to an unsaturatedoil to ‘harden’ the oil.The hydrogen is added across the double bond.Used with margarine, otherwise it would be aliquid when taken out of the fridgeOleic acid47%Palmitic acid24%Linoleic acid10%Stearic acid8%
15 Soaps + 3 Na + Soaps are salts of fatty acids. Alkaline hydrolysis is used to make sodium salts of fatty acids.+ 3Na ++ 3NaOHSodium stearate(soap)GlycerolGlyceryl tristearateCOO-Na +HydrophobictailHydrophilicend