ALDEHYDES AND KETONES

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Brittney Hicks
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1 ALDEHYDES AND KETONES Itroductio The group C=O is kow as carboyl group. This group is foud i aldehydes, ketoes, carboxylic acids, esters ad acid derivatives. I this group carbo atom makes sp hybridizatio. Therefore there are oe pi ad three sigma bods i carboyl group. Oxyge is more electroegative tha carbo i the carboyl group. 1. Aldehydes Compouds i which oe hydroge atom ad oe carbo atom are boded to the carbo atom i the carboyl group are called aldehydes. R may be alkyl or aryl group. C H O is geeral formula of aliphatic aldehydes. The simplest member is formaldehyde, HCOH. is represetatio of aldehydes. Example 1 If 0. mol of a aldehyde weighs 11.6 g, what is the molecular formula of the aldehyde? Geeral formula of aldehydes is C H O 11.6g 0.mol MM 58 g / mol MM the, C H O. Nomeclature of Aldehydes Logest chai of carbo atoms cotaiig the aldehyde group is selected. Number 1 is the carboyl carbo. Chage e edig i alkae ames with al. The positio of substituets o the chai may be idicated by the letters, α, β, γ, δ i aldehydes. Example 3 Draw the structures of followig aldehydes. a. -chloropetaal b.,3-dihydroxylpropaal c., -dibromohexaal d. 3-cyclopropyl--methyl-petaal 3. Physical Properties of Aldehydes They are polar molecules. They do ot have hydroge bods betwee their molecules; therefore they have lower boilig poits tha correspodig alcohols but higher boilig poits tha ethers. Formaldehyde is a gas at room temperature. The C to C 11 are liquids. Higher tha C 11 are solids at room temperature. Lower members are soluble i water. As the molar mass icreases solubility decreases. 4. Chemical Properties of Aldehydes 4.1 Oxidatio Reactios K Cr O 7, KMO 4 or K CrO 4 ca be used i the presece of acids. Tolles Test (Silver Mirror Test) Tolles reaget is used to detect presece of aldehyde or to distiguish betwee aldehydes ad ketoes. Methaal Ethaal -methyl propaal Formaldehyde Acetaldehyde Example Name the followig compouds a. b. c. d. Fehlig stest Fehli s reaget is used to detect presece of aldehyde or to distiguish betwee aromatic ad aliphatic aldehydes, because it does ot react with aromatic aldehydes. a. -ethyl-3-methyl petaal c. 3-hydroxyl butaal b. 3-bromo--itro butaal d. 3-pheyl propaal Reactio with KMO 4

2 Aldehydes are oxidized with KMO 4 to carboxylic acids. 4. Additio Reactios I the additio reactios pi bod i the carboyl group, C=O, is broke. Additio of Hydroge Aldehydes are reduced to alcohols i the presece of Ni ad Pt catalyst uder certai coditios. 4.3 Combustio Reactios Example 4 What is the molecular formula of a aldehyde which produces 8 g alcohol whe 5.6 L of H at STP are added? Additio of Water Additio of Alcohol 5.6 H 0.5mol m H x g.4 m 8g 0.5g 7.5g aldehyde 7.5g MMaldehyde 30 g / mol 0.5mol CHO 30g The, the formula is HCHO Example g Cu O precipitates from the reactio of 14.4 g of aldehyde with Fehlig s reaget. What is the molecular weight ad formula of the aldehyde? Additio of HCN Additio of Grigard Reaget 8.6 Cu 0. O mol mol aldehyde produces 1 mol Cu O x mol 0. mol x=0.mol aldehyde is used. 14.4g Aldehyde= =0. mol MM=7 g/mol MM C H O= C H O butaal 4 8 Example 6 How may grams of acetaldehyde ca be prepared by startig from 0 g of 80% calcium carbide? Additio of NaHSO mcac pure 0x 16g CaC 0.5mol mol CaC produces 1 mol C H the, 1 mol acetaldehyde is produced. 0.5 mol CaC produces 0.5 mol acetaldehyde. m CH4O 0.5x44 11 g produced

3 5. Preparatio of Aldehydes 5.1 Oxidatio of Primary Alcohols Ethyl pheyl ketoe Isopropyl methyl ketoe For the complex ketoes IUPAC ames are used. Logest chai of carbo atoms cotaiig the ketoe group is selected. Number 1 to the carbo atom startig earer to the carboyl carbo. Chage e edig i alkae ames with oe. 5. Dehydrogeatio of Primary Alcohols 3-methyl butaoe 3-bromo petaoe 6. Some Importat Aldehydes 6.1. Formaldehyde Colorless gas with puget odor, soluble i water. Simplest aldehyde, discovered by the Russia Chemist A. Butlerov i Widely used i the maufacture of buildig materials ad household products. It hardes proteis ad prevets them decayig. % 40 solutio of formaldehyde is called formali, used to store biological products. It is produced from methaol by dehydrogeatio with a catalyst of Cu ad silver, ad it is called Hoffma Method. 6.. Acetaldehyde Colorless, volatile ad poisoous liquid, soluble i water. Used to obtai may orgaic compouds, such as acetic acid, ethyl alcohol, sythetic rubber. It has carcioge effect. 7. Ketoes The compouds i which the two alkyl or aryl groups attached to the carboyl carbo are called ketoes. is represetatio of ketoes. R may be alkyl or aryl group. C H O is geeral formula of ketoes. Ketoes might be either symmetrical or usymmetrical with respect to alkyl groups. 8. Nomeclature of Ketoes For the simple ketoes ames of alkyl or aryl groups followed by the word ketoe are used. Example 7 Name the followig aldehydes 4-chloro--petaoe 1-pheyl-3-petaoe -ethyl cyclohexaoe 4-petee--oe Example 8 Write the structural formulae of the followig compouds. a. -petaoe b. 5-bromo-3-methyl--hexaoe c. Methyl pheyl ketoe d. Isopropyl methyl ketoe e. 3-methyl cyclopetaoe 9. Physical Properties of Ketoes Low molecular mass ketoes are liquids. More tha C 11 atoms are solids. Soluble i water by formig hydroge bods. Liquid ketoes are used as solvets i the preparatio of pait chemicals. Solubility decreases with icreasig size of the molecule. They are polar molecules but there is o hydroge bodig betwee the molecules. 10. Chemical Properties of Ketoes 10.1 Additio Reactios Additio of Hydroge Dimethyl ketoe acetoe Methyl propyl ketoe Additio of Water

4 Additio of Alcohol 11. Preparatio of Ketoes 11.1 Oxidatio of Secodary Alcohols Additio of HCN 11. Dehydrogeatio of Secodary Alcohols Additio of Grigard Reaget Additio of NaHSO Heatig Calcium Salts of Carboxylic Acids 10. Combustio Reactios Example 9 A 5 g mixture of acetoe ad dimethyl ether ca add 5. g of sodium bisulfate(nahso 3 ). What is the percetage by mass of ether i the mixture? Oly acetoe ca add NaHSO 3. 5.x58 mass of acetoe i the mixture is x=.9g 104 mass of ether = =.1 g.1 %ether by mass = x100 4% 5 Example 10 Which alcohol is formed by the reductio of 11.6 g of a ketoe with 4.48 L of hydroge gas at STP? 11.4 Additio of Water to Alkyes 1. Acetoe Smallest ketoe Colorless, volatile liquid with pleasat odor. It is soluble i water, alcohol ad ether. It is a perfect orgaic solvet used for varishes, lacquers, resis, plastics, paits, oils ad their derivatives. It burs with a blue dull flame. It is very difficult to oxidize. Preparatio of Acetoe Distillatio of wood. Heatig of calcium acetate Oxidatio of isopropyl alcohol. From acetic acid 11.6 g MM of Ketoe = 58 g / mol 0.mol C H O = = 58 = 3 C H O 3 6 The alcohol produced by the reductio of acetoe is

5 Example 11 Whe a mixture of acetoe ad propaal is burt, 4.48 L of carbo dioxide are produced at STP What is the mass of water produced at the same time? Example 1 A 11.7 g mixture of acetoe ad acetaldehyde ca be reduced by 5.6 L of H gas at STP. What is the mass of aldehyde i the mixture?

4.7 Organic Chemistry

4.7 Organic Chemistry 4.7 rgaic hemistry rude oil rude oil is a fiite resource foud i rocks. rude oil is the remais of a aciet biomass cosistig maily of plakto that was buried i mud. Alkaes Most of the hydrocarbos i crude oil