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Organic identification
This document provides information on qualitative organic analysis including: - Testing for elements like carbon, hydrogen, halogens, nitrogen, and sulfur using sodium fusion. - Using physical properties and solubility tests to obtain structural information. - Performing classification tests to identify functional groups like alkanes, alkenes, alcohols, aldehydes, ketones, carboxylic acids, esters, amines, ethers, phenols, nitriles, and nitro compounds. - Preparing characteristic derivatives to further identify organic compounds such as phenylurethanes for alcohols and arylsulfonamides for amines.
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Organic identification
- 1. PRACTICAL ORGANIC IDENTIFICATION By Lec.MzginMohammed Ayoob Mzgin.Ayoob@su.edu.krd
- 2. CONTENTS • Qualitative andQuantitative • Physical properties. • Solubility tests. • Elemental analysis. • Classification tests. • Preparation of derivatives
- 3. • Qualitative analysisof an organic compound is to determine what elements are present in the compound Qualitative Analysis of an Organic Compound
- 4. Carbon and Hydrogen •Tests for carbon and hydrogen in an organic compound are usually unnecessary an organic compound must contain carbon and hydrogen
- 5. Halogens, Nitrogen andSulphur • Halogens, nitrogen and sulphur in organic compounds can be detected by performing the sodium fusion test
- 6. CONTENTS • Qualitative andQuantitative • Physical properties. • Solubility tests. • Elemental analysis. • Classification tests. • Preparation of derivatives
- 7. • The physicalproperties of a compound include its colour, odour, density, solubility, melting point and boiling point • The physical properties of a compound depend on its molecular structure Structural Information from Physical Properties
- 8. Structural Information fromPhysical Properties • e.g. Hydrocarbons have low densities, often about 0.8 g cm–3 Compounds with functional groups have higher densities
- 9. CONTENTS • Qualitative andQuantitative • Physical properties. • Solubility tests. • Elemental analysis. • Classification tests. • Preparation of derivatives
- 10.
- 11. Organic compound Water Soluble Insoluble SolubleInsoluble Ether Next slide
- 12. Organic compound Water Insoluble Soluble NaOH Soluble HCl Insoluble NaHCO3 Insoluble Soluble A polarmolecule and molecules with larger parts Despite polar Group being present Insoluble
- 13.
- 14. 1- Compuonds ContainC,H, And Possibily Oxygene Acidic Compunds 1- Carboxylic Acids 2- Carboxylic Anhydrdes 3- Phenols Neutral Compounds 1- Aldehydes And Ketones (And Quinones) 2- Esters (Lactones) 3-carbohydrates 4-alcohols 5- Ether And Hydrocarbones
- 15. 2- Compuonds ContainC,H, N, And Possibily Oxygene Basic Compunds 1-primary Aliphatic Amines 2-secondary And Tertiary Aliphatic Amines (Including Heterocyclics). 3- Aromatic Side-chain Primary Amines. 4- Primary And Secondary Aromati Amines. 5- And Tertiary Aromatic Amines (Including Aromatic Heterocyclics). 6- Hydrazines And Semicarbzide. 7- Imine (Schiff,s Bases) Neutral nand Amphoteric Compounds 1- Amide (primary) 2- N-substitutd amide (primary and secondary). 3-Ammonium salts of carboxylic Acids 4- Aminophenols. 5- Amino Acids 6- Nitriles and isonitrile 7- Azo compounds 8- nitroso compounds Acidic Compunds 1-imides 2-some Amino Acids
- 16. 3- Compuonds ContainC,H, Halogene And Possibily Oxygene • Acyl Halide Alkyl Halide and Aromatic side-chain HalidesAmin • Aryl Halides 4- Compuonds Contain C,H, N, Halogene And Possibily Oxygene Amine Hydrohalides Acyl Halides of carboxylic acid N-halogeno Compounds Halogen-substitutd Nitro Hydrocarbons And Ethers
- 17. CONTENTS • Qualitative andQuantitative • Physical properties. • Solubility tests. • Elemental analysis. • Classification tests. • Preparation of derivatives
- 18. Halogens, Nitrogen andSulphur • The compound under test is fused with a small piece of sodium metal in a small combustion tube heated strongly • The products of the test are extracted with water and then analyzed
- 19. Halogens, Nitrogen andSulphur • During sodium fusion, halogens in the organic compound is converted to sodium halides nitrogen in the organic compound is converted to sodium cyanide sulphur in the organic compound is converted to sodium sulphide
- 20. Element Observation Halogens, as chlorideion (Cl-) A white precipitate is formed. It is soluble in excess NH3(aq). bromide ion (Br-) A pale yellow precipitate is formed. It is sparingly soluble in excess NH3(aq). iodide ion (I-) A creamy yellow precipitate is formed. It is insoluble in excess NH3(aq). Results for halogens, nitrogen and sulphur in the sodium fusion test
- 21. Results for halogens,nitrogen and sulphur in the sodium fusion test Element Material used Observation Nitrogen,as cyanide ion (CN-) A mixture of iron(II) sulphate and iron(III) sulphate solutions A blue-green colour is observed. Sulphur, as sulphide ion (S2-) Sodium pentacyanonitrosyl ferrate(II) solution A black precipitate is formed C,N,S,X X= Cl, Br,I NaCN Na2S NaX
- 22. CONTENTS • Qualitative andQuantitative • Physical properties. • Solubility tests. • Elemental analysis. • Classification tests. • Preparation of derivatives
- 23. Structural Information fromChemical Properties • The next stage is to find out the functional group(s) present to deduce the actual arrangement of atoms in the molecule
- 24. Organic compound Test Observation Saturated hydrocarbons •Burn the saturated hydrocarbon ina non- luminous Bunsen flame •A blue or clear yellow flame is observed Chemical tests for different groups of organic compounds
- 25. Organic compound Test Observation Unsaturated hydrocarbons (C =C, C C) • Burn the unsaturated hydrocarbon in a non- luminous Bunsen flame • A smoky flame is observed • Add bromine in 1,1,1- trichloroethane at room temperature and in the absence of light • Bromine decolourizes rapidly • Add 1% (dilute) acidified potassium manganate(VII) solution • Potassium manganate(VII) solution decolourizes rapidly Chemical tests for different groups of organic compounds
- 26. Organic compound Test Observation Haloalkanes (1°, 2°or 3°) • Boil with ethanolic potassium hydroxide solution, then acidify with excess dilute nitric(V) acid and add silver nitrate(V) solution • For chloroalkanes, a white precipitate is formed • For bromoalkanes, a pale yellow precipitate is formed • For iodoalkanes, a creamy yellow precipitate is formed Chemical tests for different groups of organic compounds
- 27. Organic compound Test Observation Halobenzenes •Boil with ethanolic potassium hydroxide solution, then acidify with excess dilute nitric(V) acid and add silver nitrate(V) solution • No precipitate is formed Chemical tests for different groups of organic compounds
- 28. Chemical tests fordifferent groups of organic compounds Organic compound Test Observation Alcohols ( OH) • Add a small piece of sodium metal • A colourless gas is evolved • Esterification: Add ethanoyl chloride • The temperature of the reaction mixture rises • A colourless gas is evolved
- 29. Chemical tests fordifferent groups of organic compounds Organic compound Test Observation Alcohols ( OH) • Add acidified potassium dichromate(VI) solution • For 1° and 2° alcohols, the clear orange solution becomes opaque and turns green almost immediately • For 3° alcohols, there are no observable changes
- 30. Chemical tests fordifferent groups of organic compounds Organic compound Test Observation Alcohols ( OH) • Iodoform test for: Add iodine in sodium hydroxide solution • A yellow precipitate is formed
- 31. Chemical tests fordifferent groups of organic compounds Organic compound Test Observation Alcohols ( OH) • Lucas test: add a solution of zinc chloride in concentrated hydrochloric acid • For 1° alcohols, the aqueous phase remains clear • For 2° alcohols, the clear solution becomes cloudy within 5 minutes • For 3° alcohols, the aqueous phase appears cloudy immediately
- 32. Chemical tests fordifferent groups of organic compounds Organic compound Test Observation Ethers ( O ) • No specific test for ethers but they are soluble in concentrated sulphuric(VI) acid
- 33. Organic compound Test Observation Aldehydes ( ) •Add aqueous sodium hydrogensulphate(IV) • Crystalline salts are formed • Add 2,4- dinitrophenylhydrazine • A yellow, orange or red precipitate is formed • Silver mirror test: add Tollens’ reagent (a solution of aqueous silver nitrate in aqueous ammonia) • A silver mirror is deposited on the inner wall of the test tube Chemical tests for different groups of organic compounds
- 34. Organic compound Test Observation Ketones ( ) •Add aqueous sodium hydrogensulphate(IV) • Crystalline salts are formed (for unhindered ketones only) • Add 2,4- dinitrophenylhydrazine • A yellow, orange or red precipitate is formed • Iodoform test for: Add iodine in sodium hydroxide solution • A yellow precipitate is formed Chemical tests for different groups of organic compounds
- 35. Organic compound Test Observation Carboxylic acids ( ) •Esterification: warm the carboxylic acid with an alcohol in the presence of concentrated sulphuric(VI) acid, followed by adding sodium carbonate solution • A sweet and fruity smell is detected • Add sodium hydrogencarbonate • The colourless gas produced turns lime water milky Chemical tests for different groups of organic compounds
- 36. Organic compound Test Observation Esters ( ) •No specific test for esters but they can be distinguished by its characteristic smell • A sweet and fruity smell is detected Chemical tests for different groups of organic compounds
- 37. Organic compound Test Observation Acyl halides () • Boil with ethanolic potassium hydroxide solution, then acidify with excess dilute nitric(V) acid and add silver nitrate(V) solution • For acyl chlorides, a white precipitate is formed • For acyl bromides, a pale yellow precipitate is formed • For acyl iodides, a creamy yellow precipitate is formed Chemical tests for different groups of organic compounds
- 38. Organic compound Test Observation Amides ( ) •Boil with sodium hydroxide solution • The colourless gas produced turns moist red litmus paper or pH paper blue Chemical tests for different groups of organic compounds
- 39. Organic compound Test Observation Amines (NH2) • 1oaliphatic amines: dissolve the amine in dilute hydrochloric acid at 0 – 5 oC, then add cold sodium nitrate(III) solution slowly • Steady evolution of N2(g) is observed • 1o aromatic amines: add naphthalen-2-ol in dilute sodium hydroxide solution • An orange or red precipitate is formed Chemical tests for different groups of organic compounds
- 40. Organic compound Test Observation Aromatic compounds ( ) •Burn the aromatic compound in a non- luminous Bunsen flame • A smoky yellow flame with black soot is produced • Add fuming sulphuric(VI) acid • The aromatic compound dissolves • The temperature of the reaction mixture rises Chemical tests for different groups of organic compounds
- 41. CONTENTS • Qualitative andQuantitative • Physical properties. • Solubility tests. • Elemental analysis. • Classification tests. • Preparation of derivatives
- 42. THE PREPARATION OFDERIVATIVES CARBOXYLIC ACIDS, ACID ANHYDRIDES, ACID HALIDES
- 43. CARBOXYLIC ACID S-Benzylthiuronium halideundergoes reaction with the salt of the carboxylic acid to yield the corresponding S-benzylthiuronium salt
- 44. P-NITROBENZYL OR THE4-BROMOPHENACYL ESTERS ARE PREFERRED. THESE ARE PREPARED BY TREATING THE SALTS OF THE ACIDS WITH EITHER 4-NITROBENZYL CHLORIDE OR 4 BROMIDE
- 45. ALCOHOLS The most generalderivatives of primary and secondary alcohols are the phenylurethanes and I-naphthylurethanes
- 46.
- 47. ALDEHYDES AND KETONES 2,4-dinitrophenylhydrazones,phenylhydrazones, and 4-nitrophenylhydrazones
- 48. AMIDES Indirect :- Themost general method for chemically characterizing primary amides consists in hydrolyzing them with alkali to the salt of the carboxylic acid and ammonia. Direct derivative (Xanthydrol) not common
- 49.
- 50. AMINES Arylsulfonamides are usedas derivatives for amines
- 51. A SECONDARY AMINEREACTS WITH 4- TOLUENESULFONYL CHLORIDE TO GIVE THE RYLSULFONAMIDE, WHICH IS USUALLY INSOLUBLE. Picric acid undergoes reaction with tertiary amines to yield the picrates.
- 52.
- 53.
- 54. 4-NITROBENZOATES , OR3,5DINITROBENZOATES
- 55.
- 56. QUESTION STYLES Deduce thestructure for the unknown compound(C4H6O4) according to the following observation 1-Burn with blue flame 2- No color with KMnO4 3- Give a positive test with KI/KIO3 4- Has weak peaks at 2826cm-1 and 2955cm-1 How you can distinguish each of pair compound (classically and instrumentally) 1- aldehyde and ketone. What are the roles for each of the following reagents or tests? Prepare the derivative for each of the following compounds
- 57. CONTENTS • Qualitative andQuantitative • Physical properties. • Solubility tests. • Elemental analysis. • Classification tests. • Preparation of derivatives
- 58. Compound A: insolublein water; insoluble in sulfuric acid; sodium fusion, followed by silver nitrate treatment, gave a white precipitate. Compound B: insoluble in water; quickly decolorized bromine; did not react with acetyl chloride; did not form a precipitate with 2,4-dinitrophenylhydrazine; did not form a precipitate when treated with excess iodine in aqueous sodium hydroxide solution. Compound C: insoluble in water; soluble in sulfuric acid; sodium fusion, followed by silver nitrate treatment, gave no precipitate. Compound D: soluble in water; gave a rapid reaction with acetyl chloride; did not form a precipitate with 2,4- dinitrophenylhydrazine; formed a yellow precipitate with a noxious odor when treated with excess iodine in aqueous sodium hydroxide solution. Choices: 2-propanol, cyclohexane, chlorocyclohexane, cyclohexene, diethyl ether.
- 59. Complete the followingreactions O + H3C NH2 O OH ? 2- O O O + CH3CH2NH2 ? ?+ 3- HCl NaNO2 + OH? ? NaOH 4- NH2 PhCOCl + RNH2 ? 1-
- 60. What are thenecessary information to determine the structure of an organic compound? Answer Molecular formula from analytical data, functional group present from physical and chemical properties, structural information from infra-red spectroscopy and NMR spectrometry Back
- 61. (a) Why isdetection of carbon and hydrogen in organic compounds not necessary? (b) What elements can be detected by sodium fusion test? Answer(a) All organic compounds contain carbon and hydrogen. (b) Halogens, nitrogen and sulphur Back
- 62. Let the massof the compound be 100 g. Then, mass of carbon in the compound = 40.0 g mass of hydrogen in the compound = 6.7 g mass of oxygen in the compound = 53.3 g ∴ The empirical formula of the organic compound is CH2O. Carbon Hydrogen Oxygen Mass (g) 40.0 6.7 53.3 Number of moles (mol) Relative number of moles Simplest mole ratio 1 2 1 33.3 12.0 40.0 7.6 1.0 6.7 33.3 16.0 53.3 1 3.33 3.33 2 3.33 6.7 1 3.33 3.33 An organic compound was found to contain 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Calculate the empirical formula of the compound. Answer
- 63. An organic compoundZ has the following composition by mass: (a) Calculate the empirical formula of compound Z. (b) If the relative molecular mass of compound Z is 60.0, determine the molecular formula of compound Z. Answer Element Carbon Hydrogen Oxygen Percentage by mass (%) 60.00 13.33 26.67
- 64. (a) Let themass of the compound be 100 g. Then, mass of carbon in the compound = 60.00 g mass of hydrogen in the compound = 13.33 g mass of oxygen in the compound = 26.67 g ∴ The empirical formula of the organic compound is C3H8O. Carbon Hydrogen Oxygen Mass (g) 60.00 13.33 26.67 Number of moles (mol) Relative number of moles Simplest mole ratio 3 8 1 5 12.0 60.00 33.13 1.0 13.33 67.1 16.0 26.67 8 1.67 13.33 1 1.67 1.67 3 1.67 5
- 65. (b) The molecularformula of the compound is (C3H8O)n. Relative molecular mass of (C3H8O)n = 60.0 n × (12.0 × 3 + 1.0 × 8 + 16.0) = 60.0 n = 1 ∴ The molecular formula of compound Z is C3H8O.
- 66. Relative molecular massof CO2 = 12.0 + 16.0 × 2 = 44.0 Mass of carbon in 0.22 g of CO2 = 0.22 g × = 0.06 g Relative molecular mass of H2O = 1.0 × 2 + 16.0 = 18.0 Mass of hydrogen in 0.09 g of H2O = 0.09 g × = 0.01 g Mass of oxygen in the compound = (0.15 – 0.06 – 0.01) g = 0.08 g 44.0 12.0 18.0 2.0 An organic compound was found to contain carbon, hydrogen and oxygen only. On complete combustion, 0.15 g of this compound gave 0.22 g of carbon dioxide and 0.09 g of water. If the relative molecular mass of this compound is 60.0, determine the molecular formula of this compound. Answer
- 67. ∴ The empiricalformula of the organic compound is CH2O. Carbon Hydrogen Oxygen Mass (g) 0.06 0.01 0.08 Number of moles (mol) Relative number of moles Simplest mole ratio 1 2 1 005.0 12.0 0.06 01.0 1.0 0.01 005.0 16.0 0.08 2 0.005 0.01 1 0.005 0.005 1 0.005 0.005
- 68. Let the molecularformula of the compound be (CH2O)n. Relative molecular mass of (CH2O)n = 60.0 n × (12.0 + 1.0 × 2 + 16.0) = 60.0 n = 2 ∴ The molecular formula of the compound is C2H4O2. Back
- 69. Why does thesolubility of amines in water decrease in the order: 1o amines > 2o amines > 3o amines? Answer The solubility of primary and secondary amines is higher than that of tertiary amines because tertiary amines cannot form hydrogen bonds between water molecules. On the other hand, the solubility of primary amines is higher than that of secondary amines because primary amines form a greater number of hydrogen bonds with water molecules than secondary amines.
- 70. The empirical formulaof an organic compound is CH2O and its relative molecular mass is 60.0. It reacts with sodium hydrogencarbonate to give a colourless gas which turns lime water milky. (a) Calculate the molecular formula of the compound. (b) (b) Deduce the structural formula of the compound. (c) (c) Give the IUPAC name for the compound. Answer (a) Let the molecular formula of the compound be (CH2O)n. Relative molecular mass of (CH2O)n= 60.0 n (12.0 + 1.0 2 + 16.0) = 60.0 n = 2 ∴ The molecular formula of the compound is C2H4O2.
- 71. (b) The compoundreacts with sodium hydrogencarbonate to give a colourless gas which turns lime water milky. This indicates that the compound contains a carboxyl group ( COOH). Eliminating the COOH group from the molecular formula of C2H4O2, the atoms left are one carbon and three hydrogen atoms. This obviously shows that a methyl group ( CH3) is present. Therefore, the structural formula of the compound is: (c) The IUPAC name for the compound is ethanoic acid.
- 72.