2 IX. AldehydesOxo group ( C=O) at the end of the carbon chainThe name, aldehyde, shows how we can prepare them : alcohol dehydrogenizationNomenclature: In the IUPAC system, the name of the alkane chain loses the terminal "e" and adds „al",Homologous series of the aldehydes:Methanal or formaldehydeEthanal or acetaldehydePropanal or propionaldehyde
3 IX. Aldehydes Preparation of aldehydes: Primary alcohol aldehyde oxidationPrimary alcohol aldehydeCarboxylic acid aldehydereductionOther reactions of aldehydes:Tollens’ test: Ag+ is reduced to silver metal, which in a clean glass reaction vessel forms a "silver mirror". This feature is used as a test for aldehydes, which are oxidized to carboxylic acids.R-CHO + 2AgOH R-COOH + 2Ag + H2O
4 IX. Aldehydes Other reactions of aldehydes: Tollens’ test: R-CHO + 2AgOH R-COOH + 2Ag + H2OTollens' reagent can be used to test whether the compound is a ketone or an aldehyde.When adding the aldehyde or ketone to Tollens' reagent, put test tube in a warm water bath.If the reactant under test is an aldehyde, Tollens' test results in a silver mirror.If there is no reaction then the organic substance is a ketone, as they can cannot be oxidized, due to the position of the O atom.
5 IX. Aldehydes Other reactions of aldehydes: Fehling test: R-CHO + 2 Cu(OH)2 R-COOH + Cu2O + 2 H2OIt is used as a test for the presence of reducing sugars such as glucose, fructose and maltose, or more generally for the presence of aldehydesCu2O is red and not soluble in water – red precipitate
6 IX. Aldehydes Physical properties: In the aldehydes there is no H atom which could make H-bonds.Between the aldehyde molecules there are dipole-dipole interactionsNon polar compoundsAldehydes are soluble in water but this solubility is limited :Only diluted solutions can be made from formaldehyde and acetaldehydeChemical properties:Chemically the most reactive functional group!!!! C=O
7 IX. Aldehydes1. Formaldehyde ( methanal)-Formaldehyde readily results from the incomplete combustion of carbon-containing materials.-It may be found in the smoke from forest fires, in automobile exhaust, and in tobacco smoke.-Although formaldehyde is a gas at room temperature, it is readily soluble in water.- It is most commonly sold as a 37% aqueous solution which is called formalin or formol.- An aqueous solution of formaldehyde can be used as a disinfectant as it kills most bacteria and fungi (including their spores).- It is also used as a preservative in vaccinations.- Formaldehyde preserves or fixes tissue or cells by irreversibly cross-linking primary amine groups in proteins with other nearby nitrogen atoms in protein or DNA through a -CH2- linkage.
8 IX. Aldehydes 2. Acetaldehyde ( ethanal): It is a flammable liquid with a fruity smell.occurs naturally in ripe fruit, coffee, and fresh bread and is produced by plants as part of their normal metabolism.is the chemical that causes "hangovers".- In the liver, the enzyme alcohol dehydrogenase converts ethanol into acetaldehyde, which is then further converted into harmless acetic acid by acetaldehyde dehydrogenase.
9 IX. Aldehydes- Acetaldehyde is more toxic than ethanol and is responsible for many symptoms of hangover- Most people of East Asian descent have a mutation in their alcohol dehydrogenase gene that makes this enzyme unusually effective at converting ethanol to acetaldehyde- and about half of such people also have a form of acetaldehyde dehydrogenase which is less effective at converting acetaldehyde to acetic acid. This combination causes them to suffer from the alcohol flush reaction, in which acetaldehyde accumulates after drinking, leading to severe and immediate hangover symptoms. These people are therefore less likely to become alcoholics.- The drug Antabuse also prevents the oxidation of acetaldehyde to acetic acid, with the same unpleasant effects for drinkers. It has been used in the treatment of alcoholism.
10 X. Ketones R-CO-R’Oxo group ( C=O) in the middle of the carbon chainNomenclature: In the IUPAC system, the name of the alkane chain loses the terminal "e" and adds „on",Homologous series of the ketones: (starts from C3)Propanon or acetonButanonpentanon
11 X. Ketones Preparation of ketones: Secondary alcohol keton oxidationPhysical properties of ketones:Non polar compounds but the ketones with small carbon number are soluble in water e.g. acetonBut with bigger carbon number they are immiscible in waterChemical properties:Chemically very reactive compounds
13 X. Ketones1. Aceton- Aceton is an irritant and inhalation may lead to hepatotoxic effects (causing liver damage).- it can cause permanent eye damageketosis: is a stage in metabolism occurring when the liver converts fat into fatty acids and ketone bodies (acetone, acetoacetic acid, and beta-hydroxybutyric acid) which can be used by the body for energy.Ketoacidosis: which is severe ketosis causing the pH of the blood to drop below 7.2.Ketoacidosis is a medical condition usually caused by diabetes and accompanied by dehydration, hyperglycemia, ketonuria and increased levels of glucagon.The high glucagon, low insulin serum levels signals the body to produce more glucose via gluconeogenesis, glycogenolysis and ketogenesis. High levels of glucose causes the failure of tubular reabsorption in the kidneys, causing water to leak into the tubules in a process called osmotic diuresis, causing dehydration and further exacerbating the acidosis.
14 XI. Carboxylic acidsNomenclature: In the IUPAC system, the name of the alkane chain ( including the carbon atom of the carboxylic group too) loses the terminal "e" and adds „oic", plus acidHomologous series of monocarboxylic acids(only one carboxylic group containing carboxylic acids):1. Methanoic acid = formic acid2. Ethanoic acid = acetic acid3. Propanoic acid = propionic acid4. Butanoic acid5. Pentanoic acid
15 XI. Carboxylic acidsLong chain monocarboxylic acids are called as fatty acids:e.g. palmitic acid ( hexadecanoic acid) see laterDicarboxylic acids :2 carboxylic groups containing Carboxylic acidse.g. oxalic acid HOOC-COOHmalonic acid HOOC-CH2-COOHmaleic acid HOOC-CH2-CH2-COOH
16 XI. Carboxylic acids CH3-CH2-CH2-CH2-COOH Nameing of carboxylic acids: δ γ β α1.CH3-CH2-CH2-CH2-COOHDistinguishing the carbon atoms in the chain: (IUPAC)Carbon 1: (first carbon) the carbon which is part of the carboxylic groupα is the first carbon atom after the carbon atom which is included in the Carboxylic group
18 XI. Carboxylic acids Physical properties One of the most polar compounds – strong enough for ionizationMost of them are weak acidsThey contain –OH group – they can form H- bondsCarboxylic acids are polar, and form hydrogen bonds with each other or with water – high melting and boiling pointLower carboxylic acids (1 to 4 carbons) are miscible with water,higher carboxylic acids are very much less soluble due to the increasing hydrophobic nature of the alkyl (carbon) chain.They rather soluble in less polar solvents such as ethers and alcohols.
19 XI. Carboxylic acids True solutions: small chain carboxylic acids e.g butanoic acidColloid solution : long chain carboxylic acids– they form micells : polar head, non-polar „tail”- the particle size (size of the micells) is nm
20 XI. Carboxylic acids Reactions: Chemical properties: They are weak acids with different KaReactions:Substitution in the carbon chain with halogenforming strong acid (trichloroacetic acid)2. Substitution in the carboxylic group R-COOHwith halogen forming acyl cloridewith amine group forming acyl amineAcylate or carboxylate : R-C=OAcyl group: R-C=OFormylateAcetylateO-FormylAcetyl…
21 XI. Carboxylic acids 3. Dehydratation: removing H2O Removing water from base or acid we get anhydrate║ ║O O-H2OR-COOH + HOOC-R’ R-C-O-C-R’ + H2OAcyl anhydratee.g. acetyl anhydrateInorganic anhydrate:║ ║O OH-O-H2OR-C-O-POH+ H2OR-COOH + H-O-P=OH-OOH
22 XI. Carboxylic acids 4. Oxidation: decarboxylation R-COOH R-H + CO2 5. Ester formation : alcohol + carboxylic acid (see at alcohols)In 2 steps : 1. nucleophylic addition2. water elimination
23 XI. Carboxylic acids 6. Reaction with amins (-NH2) Acid – base reaction = salt formsWater eliminationacyl amide – peptide bond formsc. Carboxylic acid + ammonia = acyl amine (H2O elimination)( substitution of the –OH group)
24 XI. Carboxylic acids 1. Formic acid ( methanoic acid) HCOOH From ant – ant acid The principal use of formic acid is as a preservative and antibacterial agent in livestock feed.When sprayed on fresh hay or other silage, it arrests certain decay processes and causes the feed to retain its nutritive value longer, and so it is widely used to preserve winter feed for cattle.In the poultry industry, it is sometimes added to feed to kill salmonella bacteria.
25 XI. Carboxylic acids 1. Acetic acid (ethanoic acid) CH3COOH -acetic acid, in the form of vinegar, has been made by bacteria of the genus Acetobacter.Given sufficient oxygen, these bacteria can produce vinegar from a variety of alcoholic foodstuffs. Commonly used feeds include apple cider, wine, and fermented grain, malt, rice, or potato mashes. The overall chemical reaction facilitated by these bacteria is:C2H5OH + O2 → CH3COOH + H2OThe acetyl (acyl) group, derived from acetic acid, is fundamental to the biochemistry.When bound to coenzyme A it is central to the metabolism of carbohydrates and fats.
26 XI. Carboxylic acids Short chain saturated monocarboxylic acids -Formic acid (methanoic acid) : HCOOH, found in insect stings-Acetic acid (ethanoic acid) : CH3COOH component of vinegar-Propionic acid (propanoic acid) : CH3CH2COOH food preservativeMedium chain saturated monocarboxylic acids-Valeric acid (pentanoic acid) : C4H9COOHShort chain unsaturated monocarboxylic acids-Acrylic acid (2-propenoic acid) : CH2=CHCOOH, used in polymer synthesis
27 XI. Carboxylic acids Fatty acids medium to long chain saturated and unsaturated monocarboxylic acidsMost commonly occurring saturated fatty acids are:Butyric acid (butanoic acid) : CH3CH2CH2COOH, found in rancid butterLauric acid (dodecanoic acid) : CH3(CH2)10COOH, found in coconut oilPalmitic acid (hexadecanoic acid): CH3(CH2)14COOHStearic acid (octadecanoic acid): CH3(CH2)16COOH