Organic Chemistry Practical Exam - Past Paper PDF

# Introduction and laboratory safety guidelines ## 1- Introduction * How to do different chemical reactions. * How to keep lab safety. * How to identify different raw materials for drug synthesis. * How to do synthesis for few drug & organic materials on lab scale. ## 2-laboratory Safety Guidelin...

# Introduction and laboratory safety guidelines ## 1- Introduction * How to do different chemical reactions. * How to keep lab safety. * How to identify different raw materials for drug synthesis. * How to do synthesis for few drug & organic materials on lab scale. ## 2-laboratory Safety Guidelines ### What you must have before entering the lab? 1. **Choose appropriate attire.** * Wear a cotton robe with least tendency for fire. * Wear closed-toe shoes. * Tie your hair if you are working with fire. 2. **Wear eye glasses at all times during the lab!** * Your eyes are sensitive, and even a small bit of a chemical in your eye could permanently blind you. 3. **Wear gloves as they will prevent spillages from damaging your skin.** * Use gloves that are appropriate to the chemicals you are working with. * Thin latex gloves will not protect you if you are working with highly corrosive materials. * If you spill anything onto any glove, put the chemical away as safely and quickly as possible and take off your gloves. Wash or dispose of them correctly. 4. **Wear a suitable mask if you are proceeding an experiment those producing dangerous gases.** 5. **Know where safety equipment is.** * Know the locations of fire extinguishers. ## Precautions during proceeding the lab 1. **Wear eye glasses at all times during the lab.** 2. **Take Data During the pre-Lab** * Put data directly in your lab book rather than transcribing from another source. * Read the experiment in advance. 3. **Follow the procedure carefully.** * Read the procedure of each carefully before stating it. * Do not deviate from the procedure unless your teacher says you may. 4. **Don't Eat or Drink in Lab.** * It's dangerous. You may have harmful chemicals on your hands which could be transferred to food and ingested. 5. **Don't Play Mad Scientist.** * Don't carelessly mix chemicals! * Pay attention to the order in which chemicals are to be added to each other and do not deviate from the instructions. 6. **Don't use the phone during the lab: You will interrupt your colleagues.** 7. **Don't smoke that may lead to a serious problem.** ## On dealing with chemicals 1. **Don't touch the chemical directly.** * Even chemicals that mix to produce safe products should be handled carefully. * The reaction of hydrochloric acid and sodium hydroxide could break your glassware or pour the reactants onto you if you aren't careful. 2. **Add acids to water instead of the other way around.** * Adding water to an acid will cause heat to build up and cause an explosion. * Use disposable pipettes instead of pipetting by mouth. ## Types of tools you may deal with - Test tube - Beakers - Holder - Brush - Rack # Physical properties of unknown organic compounds ## 1- Condition - **Solid** - **Crystals** - micro e.g oxalic acid - macro e.g resorcinol, a and ẞ naphthol - **Powder** - macro e.g sod. acetate - micro e.g. sod. acetate - **Liquid** - **Mobile** e.g. ethanol - **Oily** e.g. benzaldehyde, aniline - **Viscous** e.g. glycerol > **Note:** For liquids, it must be noted however it is true liquid (doesn't contain water) (e.g. benzyl alcohol) or a solution (contain water) (e.g. formalin) by applying CuSO4 test. ### Copper sulfate test * Place few drops of unknown liquid + few crystals of anhydrous copper sulphate in a watch glass. * The color of copper sulphate will not be changed with true liquids while with solutions it turns blue. (Do blank using water) ## 2- Color * As seen ## 3- Odor * **Characteristic:** e.g.acetone * **Fishy:** e.g. aniline * **Bad apple:** e.g. acetaldehyde * **Odorless:** e.g. glycerol ## 4- Solubility ### Method * Place 0.1-0.2g of the solid or 0.2 ml of the liquid in a test tube, add 5 ml water (solvent) & shake. * If the compound dissolves completely record it as soluble. * For solids: soluble, insoluble * For liquids: miscible, immiscible. ### Solubility is tried as the following sequence: 1. **In cold water:** * If the material is soluble/miscible in water, then it is tested by litmus paper to detect however it is neutral, acidic or basic material. * For liquids immiscible in water, it is mentioned whether it is heavier or lighter than water. * Liquids are heavier than water: e.g. benzaldehyde, aniline, methyl salicylate and chloroform * Liquids are lighter than water: e.g. benzene, toluene and ethyl acetate 2. **In 10% NaOH:** * If the unknown substance is insoluble in water try its solubility in 10% NaOH. * If the material is soluble/miscible in 10% NaOH and re-precipitated by conc. HCl, then it is acidic material(e.g. salicylic acid). 3. **In dilute HCl:** * If the substance is insoluble in water & 10% NaOH, try its solubility in dil. HCl. * If the material is soluble/miscible in dil. HCl and re-precipitated by 30% NaOH, then it is a basic material. (e.g. aniline) * If the material is insoluble/immiscible in dilute HCl i.e. insoluble/immiscible in all reagents, then it is neutral. ## Important Note: * For any acidic material, NaCO3 test is done to detect how strong or weak acid it is. ### Na2CO3 test: * If the substance is liquid: 0.5 gm Na2CO3 powder is added to 2 ml of the liquid. * If the substance is solid: 0.5 gm of the solid material is added to 3ml saturated solution of Na2CO3 - **Effervescence of CO2:** So, strong acid - **No effervescence:** So, weak acid > E.g. salicylic acid > E.g. phenol # Chemical properties of unknown organic compounds ## I-Action of ferric chloride (FeCl3): * A color or a precipitate is produced from the reaction of FeCl3 with different classes of organic compounds: 1. **Phenols** * Phenol (solution in water) → violet color * Salicylic acid (suspension in water) → violet color * B-naphthol (solution in alcohol) → green color 2. **Amines** * Aniline (solution in dil. HCl) → olive green color. 3. **Carboxylic acids (on neutral solution of the acid)** * Formic acid and acetic acid → blood red color * Lactic, citric, oxalic and tartaric acids→ lemon yellow color (must do blank*) * Benzoic acid → buff precipitate ### How to prepare a neutral solution of an acid? * Take 0.5 g of acid + slight excess ammonia solution (litmus paper red→ blue) and boil gently till no amm. odor (litmus paper red→red) then cool and add few drops of FeCl3. #### Important Note: * The solution should be neutral for this reaction to be successful. * Excess of acid usually inhibits the production of color and excess of alkali gives a reddish brown precipitate of ferric hydroxide. ### How to make blank* test? * **Test solution:** 2 ml of a neutral solution of an acid + FeCl3 drops * **Blank solution:** 2 ml water + FeCl3drops(the same drops as solution test) > Compare the color produced in both. ## II-Action of 30%NaOH: * A color, odor or a precipitate is produced from the reaction of 30% NaOH with different classes of organic compounds: 1. **Aliphatic aldehydes (except formaldehyde)** give yellow to orange resin * E.g. acetaldehyde. 2. **Ammonium salts** * Ammonium oxalate → ammonia gas on cold and on hot. 3. **Amides** * Urea, acetamide....→ammonia gason hot. 4. **Sugars** * Glucose, lactose, fructose.....→carmel like odor and yellow solution turn to brown on hot. 5. **Esters (hydrolysis to alcohol and Na salt of acid) ** * Methyl salicylate → white precipitate of Na salicylate on cold 6. **Acetanilide:** heating with 30%NaOH(hydrolysis to aniline and sodium acetate) give fishy odor and oily droplets of aniline # scheme for Identification of unknown organic compounds ## Unknowns - **Liquids (4)** * Aniline * Acetic acid * Glycerol * Toluene - **Solids (6)** * Na-salisylate * B-naphthol * Benzoic acid * Na-benzoate * Glucose * Acetanilide ## (I) Liquids * 1ml of an unknown compound (Aniline, Glycerol. Toluene or Acetic Acid) is mixed with 5 ml of H2O, shaking the mixture without too much force, * The mixture can be separated into three categories based on their relative densities: * Lighter than H2O: The unknown compound is Toluene. * Heavier than H2O: The unknown compound is Aniline * Miscible with H2O: The unknown compound is Glycerol or Acetic Acid. - **For the Aniline category:** * Perform a FeCl3 test: An olive green color changes to blue when heated. - **For the Glycerol or Acetic Acid category:** * Perform a Na2CO3 test: Acetic Acid will show effervescence and Glycerol will show no effervescence. * Perform a FeCl3 test: Acetic acid will turn blood red in color. ## (II) Solids * 0.5gm of an unknown compound (Na-benzoate, Na-salicylate, B-Naphthol, Benzoic acid, Glucose or Acetanilide) is mixed with 5 ml of H2O, shaking well. * The mixture can be separated into two categories based on whether they are soluble in water or not: - **Soluble in water category :** * The unknown compound is Na-salisylate, Na-benzoate or Glucose. * Perform a FeCl3 test: Na-salisylate turns violet, Na-benzoate turns buff and Glucose will have no color change or turns yellow. - **Insoluble in water category:** * The unknown compound is B-Naphthol, Benzoic acid or Acetanilide * Perform a 30% NaOH and heat the mixture. * If the mixture will turn into a carmelized solution, it's Glucose. * If the mixture shows a fishy and oily droplets, it's Acetanilide. ## For solids insoluble in water ( B-naphthol, Benzoic acid, Acetanilide ) * 0.5gm of an unknown compound (B-naphthol, Benzoic acid, Acetanilide) is mixed with 5 ml of 10%NaOH, shaking well. * The mixture can be separated into two categories based on whether they are soluble in NaOH or not: - **Soluble in NaOH category:** * The unknown compound is Benzoic acid or B-naphthol. * Perform a FeCl3 test: Benzoic acid will show a buff precipitate while B-Naphthol will show a green color. - **Insoluble in NaOH category:** * The unknown compound is Acetanilide. * Heat the mixture (C.T) with 30% NaOH: B-naphthol will produce a fishy odor and oily droplets.