H H H O. Pre-Lab Exercises Lab 6: Organic Chemistry. Lab 6: Organic Chemistry Chemistry Define the following: a.

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1 Lab 6: Organic hemistry hemistry Define the following: a. ydrocarbon Pre-Lab Exercises Lab 6: Organic hemistry Name Date Section b. Saturated hydrocarbon c. Unsaturated hydrocarbon 2. The formula of the ester methyl butyrate is 3 2 2OO 3. It s shape is below: O O The formula for ethyl butyrate is 3 2 2OO 2 3, and this is one of the esters we ll be mixing. Draw it s shape (int: it s very similar to the ester above!): 3. Draw the structure of ethanol, one of the alcohols we ll be testing. Page 1 of 5

2 Lab 6: Organic hemistry hemistry 100 hemistry 100 Lab 6: Organic hemistry DISUSSION Organic chemistry is defined as the study of carbon-containing molecules. In this lab we will look at several types of carbon molecules: saturated and unsaturated hydrocarbons, alcohols and esters. Except for their reaction with oxygen (combustion), saturated hydrocarbons are not very reactive. Paraffin wax, for example, is a mixture of saturated hydrocarbons that is sometimes used to seal home-canned jams and other foods. The wax can be in contact with acidic foods and oxygen for long periods (at room temperature) without undergoing a reaction. Unsaturated hydrocarbons, on the other hand, are much more reactive than saturated hydrocarbons because of the presence of double and triple bonds. This part of the experiment illustrates the difference in reactivity of two hydrocarbons toward some strong oxidizing agents. The alcohol functional group can also be oxidized by oxidizing agents, forming an aldehyde or a carboxylic acid. The reaction of ethanol with potassium dichromate is the basis of the Breathalyzer test used to detect alcohol in the exhaled breath of someone suspected of driving while intoxicated. Esters can be made from acids and alcohols in the presence of sulfuric acid, which helps remove the water formed in the reaction. Many esters have distinct tastes and odors, and are components of both natural and artificial flavors. Some esters are soluble, while some will separate out as an insoluble layer. Pay attention to this and note it in your observations. Some words of warning: many of the chemicals used in this experiment are corrosive and toxic. Avoid contact of the chemicals with skin, eyes, and clothing. Some of the chemicals will be located in the fume hood. Keep them there to avoid exposure to their vapors. Also, many of the chemicals are flammable. Make sure there are no flames in the lab during this experiment. Saturated and Unsaturated ydrocarbons PROEDURES 1. Into each of two small test tubes, place about 1 ml of hexane, a saturated hydrocarbon. (A 1 ml sample in a small test tube will be about 1 cm high.) 2. Into each of two other test tubes, place about 1 ml of cyclohexene, an unsaturated hydrocarbon. 3. To a sample of hexane and a sample of cyclohexene, add five drops of bromine water (Br 2 dissolved in water). Bromine is a strong oxidizing agent used to disinfect water and to bleach silk and other fibers. Two layers will form in the test tubes. Agitate the contents of the test tubes, and watch for evidence of a reaction, such as a color change, the formation of a solid, etc. You may need to wait a minute or two to decide if a reaction occurred. Bromine will dissolve in hydrocarbons, so if they turn a color similar to the color of the bromine water, do not take that as evidence of a reaction. Record your observations on the report sheet. 4. To the other sample of each hydrocarbon, add five drops of a solution of potassium permanganate (0.1 M KMnO 4, used in many bleaching and disinfecting processes). Again there will be two layers. Agitate the contents of the test tubes, and watch for evidence of a reaction (such as a color change or formation of a solid). Record your observations. 5. Empty the contents of the four test tubes in the Organic Waste container provided. DO NOT pour them down the drain. Wash the test tubes with soapy water and rinse them well before proceeding. Page 2 of 5

3 Lab 6: Organic hemistry hemistry 100 Oxidation of Alcohol 1. Into two small test tubes, place 1 ml samples of ethanol. 2. Into two other test tubes, place 1 ml samples of isopropyl alcohol (rubbing alcohol). 3. Add five drops of potassium permanganate solution to one sample of each alcohol, and five drops potassium dichromate solution (and a few drops of 3 M sulfuric acid) to the other sample of each alcohol. Agitate the contents of the test tubes, and watch for evidence of reaction. One or more of the reactions may be slow, so be patient. Record your observations. 4. The contents of these test tubes should be disposed of in the eavy Metal waste container. Rinse each test tube well with water. Esters 1. Add about 125 ml of water to a 250 ml beaker, and heat the water on a hot plate to o. It is very important to get your water stable within this temperature range before placing your ester test tubes in it! 2. While the water is heating, number six small, dry test tubes. Add chemicals to the test tubes as indicated below. The name of the ester that will be made in each tube is given in parentheses. a. Tube 1: 10 drops ethanol + 10 drops glacial acetic acid (Ethyl acetate) b. Tube 2: 10 drops methanol g salicylic acid (Methyl salicylate) c. Tube 3: 20 drops isoamyl alcohol + 10 drops glacial acetic acid (Isoamyl acetate) d. Tube 4: 20 drops octyl alcohol + 8 drops glacial acetic acid (Octyl acetate) e. Tube 5: 9 drops benzyl alcohol + 10 drops butyric acid (Benzyl butyrate) f. Tube 6: 6 drops ethanol + 10 drops butyric acid (Ethyl butyrate) 3. To each test tube, add 5 drops of concentrated (18 M) sulfuric acid. AUTION - This acid is very corrosive. 4. Observe your test tubes while making the esters. Note any changes in color, consistency, smell, solubility, etc. 5. andle the bottle very carefully and make sure to avoid any spills. Agitate the contents of each test tube, then place them in the hot water bath for 10 minutes. If any of the contents begin to boil, remove them from the water bath. Record your observations. 6. After 10 minutes, place the test tubes in a test tube rack and allow them to cool to room temperature. 7. Working one at a time, hold the test tube near (but not directly under!) your nose. Use your hand to fan the odor toward your nose. Describe the odor on your report. You can compare the odor to familiar smells (e.g. peach mixed with banana and orange Tang ), or give a more general description (tangy, sharp, sweet, sour, etc.). The more detailed you are in your description, the easier it will be to identify the unknown ester. 8. Repeat the smelling process with each of your 6 esters. If you want to, you can clear the palate by smelling some coffee crystals in between esters. This will help keep them from all smelling the same. 9. Obtain an unknown ester, which is one of the six esters you have made, record its number, and carefully smell it like you did your other 6 esters. Remember, smell the ester by fanning toward your face and DO NOT place the vial directly under your nose. Identify the unknown ester by its odor and name it. 10. Dispose of the contents of the six test tubes in the waste containers provided. Wash them with soapy water and leave the bench area and all glassware clean and ready for the next lab section. Page 3 of 5

4 Lab 6: Organic hemistry hemistry 100 Lab Station heck Out # REPORT Name Lab Partner Date Section Saturated and Unsaturated ydrocarbons Bromine Water exane yclohexene Permanganate exane yclohexene Oxidation of Alcohol Permanganate Ethanol Isopropyl Alcohol Dichromate Ethanol Isopropyl Alcohol Page 4 of 5

5 Lab 6: Organic hemistry hemistry 100 Esters Description of Odor Ethyl Acetate Methyl Salicylate Isoamyl acetate Octyl acetate Benzyl Butyrate Ethyl Butyrate Unknown Ester # Identity of unknown ester: Post-Lab Analysis 1. Draw the structure of hexane. 2. Explain your observations of what happened when you mixed hexane and bromine water. Page 5 of 5