NOVISI KOMLA OKLU INDEX #: 5030010 CHEMISTRY 1 TITLE: ORGANIC FUNCTIONAL GROUP IDENTIFICATION LAB DEMONSTRATOR: MR. OPOKU GYAMFI 8TH APRIL, 2011 Aims and Objectives: 1. To know the steps involved in the identification of organic functional groups. 2. To determine the functional groups in some unknown compounds. 3. To be able to study the chemical properties of commonly encountered functional groups. INTRODUCTION A functional group is a group of atoms that have same molecular formula but different chemical properties. Examples are alkanoic acid, alkanol, alkanone, esters etc. The solubility behaviour of an unknown compound will serve to classify it into one of the three main divisions, namely, acidic, basic and neutral. This information, with the aid of elemental analysis forms the basis for the subsequent systematic search to identify the functional group(s) present. When an organic compound contains more than one functional group, the classification is generally based upon the one which is most easily detected and manipulate. Thus benzoic acid, p-methoxybenzoic acid and p-nitro benzoic acid will be classified as acids both by the solubility test and the class reaction. The distinction between true acids and weakly acidic pseudo acids are made by observing the nature of the reaction with sodium hydrogen carbonate. An organic compound that dissolves in dilute hydrochloric acids usually contains nitrogen. Examples of these nitrogen compounds are primary, secondary and tertiary amines. Neutral oxygen derivatives of the hydrocarbons are soluble only in concentrated sulphuric acid, as are alkenes. APPARATUS 1. Test tubes 2. Litmus paper 3. Retort stand CHEMICALS 1. 2. 3. 4. 5. 6. Distilled water 5% NaOH 5% NaHCO3 5% HCL Conc.H2SO4 Unknown sample A,B,C PROCEDURE The unknown substances were dissolved in water. Blue and red litmus papers were placed in the solution to test whether the compound is acidic, basic or neutral. Portions of the unknown substances were placed in test tubes and the following solutions were added to them respectively-5% NaOH, 5% NaHCO3, 5% HCL and conc. H2SO4. SOLUBLE IN a) Water + Litmus Paper A B C b) 5% NaOH A B C c) 5% NaHCO3 A B C d) 5% HCl A B C e) Conc. H2SO4 A B C OBSERVATION NATURE Soluble, changed blue litmus paper to red Soluble, no colour change on litmus paper Insoluble, changed blue litmus paper to red Acidic Neutral Acidic Soluble Soluble Insoluble Acidic Acidic Not Acidic Effervescence, Soluble Soluble Insoluble Strongly acidic Strongly acidic Not strongly acidic Soluble Soluble Insoluble Nitrogenous base Nitrogenous base Not nitrogenous base Soluble Soluble Dark green solution, Soluble Contains Oxygen in a form Contains Oxygen in a form Doesn’t contain oxygen in any form DISCUSSION From the table of results, it is seen that sample A, when added to water turned blue litmus paper red. This could mean that sample A is acidic. Also sample B turned blue litmus paper red when dissolved in water which could make sample B acidic. When water was added to the sample G, the sample was soluble. When the red and blue litmus paper was put into the solution to check its pH, it was realized that there was no change in the colour of either the red or blue litmus paper. This means that the solution was neutral. When 5% NaOH was added to the samples A, B and C, A and B dissolved. This could mean that the samples A and B are acidic. Also when conc. Sulphuric acid was added to the samples I, G and H, they all dissolved. This could mean that the samples A, B and C contain compounds that are neutral and may contain oxygen. When 5% HCL was added to the samples A and B, they were soluble this could mean that samples A and B contains nitrogenous bases compounds. When 5% NaHCO3 was added to the samples A, B and C, there was effervescence with A which means a gas was evolved, probably carbon dioxide and it dissolved. B dissolved with no effervescence. This could mean that A and B are strongly acidic. CONCLUSION From the above experiment, it can be concluded that the sample A is strongly acidic and may contain a compound which contains oxygen. Also, sample B may contain acidic, neutral and nitrogenous compounds. Sample C may contain compounds that are acidic. The aim of the experiment, thus to identify the functional group was accomplished. PRECAUTIONS 1. 2. 3. 4. All test tubes were rinsed to avoid contamination. Right volumes of the reagents were used. Hands were washed after completing the experiments. The solution was shaken well before its solubility determined. REFERENCES Organic Chemistry by Seghan N Ege Fundamentals of organic chemistry by G.B Butler and K.D Berlin Vogel’s Practical Organic Chemistry. PRE-LAB 1 1. Saturated solution: It is a solution in which no more solute can dissolve in a given solvent at a given temperature. Unsaturated solution: Is a solution more solute can dissolve in the given solvent at a given temperature. Thus, the solvent is in excess. Supersaturated solution: Is a solution 2. Drying agents: Calcium Sulphate (CaSO4) Potassium Carbonate Magnesium Sulphate Calcium Chloride Sodium Sulphate 3. Organic Compound Melting Point (oC) Oxalic acid 166 Salicylic acid 158 Cinnamic acid 133 Benzoic acid 122 Acetanilide 113 Citric acid 100 Vanillin 80 Palmitic 63 Benzophenone 49 Decreasing Melting The melting point of a substance depends on the intermolecular forces existing between the molecules of the compound. Hydrogen bonds are stronger than Van der Waal’s forces. From the table, hydrogen bond decreases down from oxalic acid to benzophenone. Hence, the decreasing orders of the melting point. 4. (a) When ethanol is added to the mixture, all the compound will dissolve except alum. To obtain the alum, the solution is filtered, and the alum is collected as the residue. (b)The mixture is first dissolved in ether and filtered to obtain sugar and alum from the solution. Ethanol is then added to the residue dissolve the sugar leaving the alum undissolved. The ethanol solution is distilled to separate the ethanol from the solution. The sugar left is recrystallised, washed and dried to obtain the sugar.
