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LAB 7. ORGANIC COMPOUNDS: STRUCTURE & PROPERTIES PURPOSE: To discover physical and chemical properties of organic compounds. To identify organic functional groups from assembled molecular models. SAFETY CONCERNS: Always wear safety goggles. Hydrocarbons are flammable. Keep small model pieces away from young children who may swallow them. HYDROCARBONS: Hydrocarbons are compounds made primarily of carbon and hydrogen. An alkane is a hydrocarbon containing only single bonds. An alkene contains one or more carbon-carbon double bonds. Alkynes have one or more carbon-carbon triple bonds. Aromatic hydrocarbons contain a circular pattern of double and single bonds where the double bonded electrons can travel completely around the ring. Saturated hydrocarbons contain no double bond or triple bonds. Alkanes are saturated. Unsaturated hydrocarbons contain double or triple bonds. Alkenes, Alkynes, and Aromatic hydrocarbons are all unsaturated. Examples: Alkane Alkene Alkyne Aromatic (saturated) (unsaturated) (unsaturated) (unsaturated) Propane Propene Propyne Benzene H H H H H C C C H H H H H C C C H H H H H H H C C C H H H H C C C C C C H H H PHYSICAL PROPERTIES: Volatility: Because of the small difference in electronegativities between carbon (C=2.5) and hydrogen (H=2.1), hydrocarbons are characteristically nonpolar. Since hydrocarbons do not have partially negative or partially positive atoms there is minimal attraction between hydrocarbon molecules. Thus, hydrocarbons require less energy to evaporate or vaporize than do polar compounds. Small hydrocarbons require less energy to vaporize than large ones. They are highly volatile. Odor: The volatile nature of hydrocarbons causes them to vaporize and move through the air. These air-borne molecules reach our noses and we smell them. Many hydrocarbons have characteristic odors. CH110 Lab 7. Organic Compounds (W14) 73 Solubility: The nonpolar character of hydrocarbons allows them to have minimal attraction to other hydrocarbons but causes them to repel polar compounds such as water. Density: Nonpolar hydrocarbons have minimal attraction to each other so hold together loosely. They have low density. Polar compounds, on the other hand, attract each other and bind close. Water has a lot of hydrogen bonding and is particularly dense. CHEMICAL PROPERTIES: Combustion: Hydrocarbons easily combust in the presence of oxygen. They are commonly used for fuel. Wood, fuel oil, gasoline, diesel, and candle wax are all common flammable hydrocarbons fuels. CH4 + methane 2O2 CO2 oxygen carbon dioxide + 2H2O water Not all hydrocarbons will react with the same amount of oxygen so when burning in a normal atmosphere they may appear very different. Aromatic hydrocarbons, for example, burn very dirty in that they undergo incomplete combustion and produce a lot of soot. Small hydrocarbons and alcohols are more likely to completely combust and burn cleanly, with very little or no soot. MOLECULAR MODELS: Models are often used by chemists to visualize molecular structures. Structural differences between functional groups provide reasons for differences in chemical reactivity. In preparation for this laboratory exercise, review the sections in your text book pertaining to molecular structure of compounds such as alkanes, alkenes, alkynes, aromatics, alcohols, ethers, aldehydes, ketones, carboxylic acids, and esters . Be able to identify each of these functional groups and be able to write condensed and full structural formulas for them. Alcohols and ethers can be viewed as derivatives of water where one or both of water’s H atoms have been replaced by a carbon group (R). The –OH group of an alcohol is called a hydroxyl group. Water Alcohol General Structure H-O-H Specific Example H H R-O-H H C C O H H H Ethyl Alcohol Ethanol H H H Ether R-O-R H C C O C H H H H Ethyl Methyl Ether Methoxyethane 74 CH110 Lab 7. Organic Compounds (W14) Aldehydes and Ketones contain the carbonyl group. Aldehydes have one or two hydrogen atoms attached to the carbonyl carbon. Ketones have two carbon groups bonded to the carbonyl carbon. General Structure Carbonyl Specific Example O C Aldehyde O O H C H or O H O H C H H C C H R C H H Ethyl aldehyde Ethanal Formaldehyde Methanal Ketone H O H O H C C C H R C R H H Acetone Propanone Carboxylic Acids contain both the carbonyl group and the hydroxyl group; the hydroxyl group must be bonded to the carbonyl carbon. Together the carbonyl gropu and the hydroxyl group are called the carboxyl group. Esters are derivatives of carboxylic acids. The hydrogen atom of the carboxyl group has been replaced by a carbon group. General Structure Carboxyl Specific Example O C O H Carboxylic Acid O O H C O H O or H O H C O H R C O H H Formic Acid Methanoic Acid O Ester O H C O R O or R C O R H C C O H H H H C O C C H H H Ethyl Formate Ethyl Methanoate CH110 Lab 7. Organic Compounds (W14) Acetic Acid Ethanoic Acid H O H H C C O C H H H Methyl Acetate Methyl Ethanoate 75 NOTES: PROCEDURES: 1 The beakers must have identical surface areas so that each of the liquids has the same amount exposed for evaporation. ACTIONS: I. PHYSICAL PROPERTIES: A. Volatility: 1. Obtain three 50mL beakers of identical1 size. Label2 them #1, #2, #3. 2 2. Into beaker #1 put 5 mL of water. Into beaker #2 put 5 mL of ethanol. Into beaker #3 put 5 mL of hexane. 3. Carefully weigh each beaker from Part IA on the electronic balance 3 and record the masses on your report sheet. Some beakers have a white patch where labels can be written with pencil. Otherwise use a grease pencil to clearly distinguish your beakers. 3 4 4. Weigh each beaker again every 15 minutes and record the masses. 5. On the report sheet make a graph of the total mass lost by each substance every 15 minutes. Draw a straight line through the graph points to show the linear relationship for the evaporation of each liquid. Compare to determine relative volatility.5 6. In between beaker weight readings continue working on other parts of the lab. Use the same balance for each measurement to avoid errors. 4 Continue working other parts of the lab come back every minutes to weigh beakers in this part. on and 15 the 5 A volatile liquid evaporates very easily. B. Odor: 7. Waft the vapors6 of each of the 3 beakers and record your observations on the report sheet.7 C. Solubility in Water: 8. After your mass data over 60 minutes has been collected from Part IA. Pour some of the water from beaker #1 into beaker #2 with the ethanol. Swirl to mix. Pour the rest of the water into beaker #3 with the hexane.8 Swirl to mix. 9. Check beakers #2 and #3 for layers.8 Using the diagrams given record your observations about the solubility of each hydrocarbon in water. Explain the presence of any layers formed. Never smell a chemical directly but instead gently “waft” the vapors toward your nose. 7 We are using hexane to represent the odor of all hydrocarbons although not all hydrocarbons smell exactly the same. Compare the general properties of the odor of water, hydrocarbon, and alcohol. 8 D. Density: 10. Observe beaker #3 with the water and hexane mix. Determine which substance (water or hexane) has the greatest density. On the report sheet label the identity of each layer. 11. Dispose of the contents of beaker #3 in a designated hydrocarbon waste container. 76 6 CH110 Lab 7. Organic Compounds (W14) If you are not certain that an insoluble layer is forming or if the layers are to small then add a couple more mLs of water or hexane and see if a layer gets bigger. II. CHEMICAL PROPERTIES: A. Combustion (Instructor Demo): 1. Line up 3 clean and dry9 watch glasses about 6 inches apart in a fume hood. 2. Onto watch glass #1 put 10 drops ethanol. (C2H5OH) (an alcohol) Onto watch glass #2 put 10 drops of hexane. (C6H14) (an alkane) Onto watch glass #3 put 10 drops toluene. (C6H5CH3) (an aromatic)10 3. Ignite each liquid with a burning wood splint and compare the colors and types of flames produced by each hydrocarbon as they burn together. 11 4. Record your observations. 9 The glassware must very dry. If any water is present your results may not be accurate. 10 We are using toluene, (methyl benzene) as a representative of the family of aromatics. It is less toxic than benzene because it is not as flat (planar) so therefore does not intercollate as readily into our spiral DNA. 11 Observe if the hydrocarbons ignited rapidly or if they were slow to ignite. Observe if there is a “clean” flame or a “sooty” flame. III. MOLECULAR MODELS: Examine the numbered models provided. Each of the models represents an organic molecule that contains one or more oxygen containing functional groups. In the space provided on the Report Sheet, give the information requested for each model. 1. 12 A. Write the structural formula for this compound. B. Enclose the carbonyl group in a rectangle and label it “carbonyl group”. C. Write the name of the compound class.12 D. Is this compound easily oxidized, reduced, hydrolyzed, or esterified? 13 (circle those that apply) E. What is the IUPAC name of this compound?13 F. What is the common name of this compound? 13 Determine the functional group class such as alcohol, ether, aldehyde, ketone, carboxylic acid, or ester. 13 You may need to consult your text book for this information. 2. A. B. C. D. E. F. G. Write the structural formula for this compound. Circle and label the polar region of this compound. Box and label the non-polar region of this compound. Write the name of the compound class.12 Will this compound form hydrogen bonds? (Yes or No?) Is this compound soluble in water? (Yes, No, or partially?) Is this compound easily oxidized, reduced, hydrolyzed, or esterified? 13 (circle those that apply) 3. A. Write the structural formula for this compound. B. Write the name of the compound class.12 C. Name the two classes of compounds that would result from the hydrolysis of this compound. CH110 Lab 7. Organic Compounds (W14) 77 4. A. Write the structural formula for this compound. B. Write the name of the compound class.12 C. Is this compound easily oxidized, reduced, hydrolyzed, or esterified? 13 (circle those that apply) D. Is this compound soluble in water? (Yes, No, or partially?) E. What is the Common name of this compound?13 5. A. B. C. D. Write the structural formula for this compound. Write the name of the compound class.12 Circle the acidic hydrogen in this compound. Is this compound a strong acid, weak acid or a neutral compound? (circle one) E. Is this compound soluble in water? (Yes, No, or partially?) F. What is the IUPAC name of this compound?13 G. Write an equation showing how this compound ionizes in water.14 6. A. Write the structural formula for this compound. B. Write the name of the compound class.12 C. Is this compound easily oxidized, reduced, hydrolyzed, esterified, or reactive with alcohols? 13 (circle those that apply) D. Is this compound soluble in water? (Yes, No, or partially?) E. Give the IUPAC name for this compound. 78 CH110 Lab 7. Organic Compounds (W14) 14 Do not use generalizations but rather write an equation showing the ionization of the specific molecule in question. LAB 7. ORGANIC COMPOUNDS: NAME_____________ DATE______________ PRE LAB EXERCISES: 1. Draw the structural formula for each of these hydrocarbons: Ethanol Hexane Toluene Formaldehyde 2. Match the following terms with the structures they represent: A. 1.___ Alcohol 2.___ Alkane 3.___ Alkene F. H H C C H CH3 B. Alkyne 5.___ Aromatic 6.___ Aldehyde 7.___ Carboxylic Acid C. 9.___ Ester Ether 10.___ Ketone _____3. O CH3CH2C O CH2CH3 H. H H C C C H H D. O CH3CH2CCH3 J. H H 8.___ CH3CH2CH G. H H H OH H C C C C H H H H H 4.___ O O CH2 CH3 H CH3CH2C OH H H E. H H H H H C C C C H H H H H K. CH3CH2CH2OCH2CH3 The black soot is given off when certain hydrocarbons are burned because __ A. the fuel is undergoing complete combustion in the presence of oxygen. B. carbon dioxide and water mix to give a black powder. C. there is not enough oxygen present in the environment to combust that much fuel. D. more than one of these. CH110 Lab 7. Organic Compounds (W14) 79 80 CH110 Lab 7. Organic Compounds (W14) LAB 7. ORGANIC COMPOUNDS: NAME___________________ PARTNER_________DATE___ REPORT: I. PHYSICAL PROPERTIES: A. Volatility: a. Mass at Start b. Mass lost in zero min c. Mass at 15 minutes d. Total g’s lost from beginning e. Mass at 30 minutes f. Total g’s lost from beginning g. Mass at 45 minutes h. Total g’s lost from beginning i. Mass at 60 minutes j. Total g’s lost from beginning #1 + Water #2 + Ethanol #3 + Hexane Mass in grams Mass in grams Mass in grams Og Og Og (a-c) (a-c) (a-c) (a-e) (a-e) (a-e) (a-g) (a-g) (a-g) (a-i) (a-i) (a-i) Mass lost by Water (#1), Ethanol (#2), and Hexane (3#) Total Mass Lost From the Beginning (in grams) 0 15 (a-c) 30 (a-e) 45 (a-g) 60 (a-i) Time (in minutes) Volatility Results Summary: Rank the substances in order of decreasing volatility. Most volatile > > A. On the given structures of ethanol label any partially positive (+) or partially negative (-) atoms. B. Draw a dotted line (…..) to show Hydrogen bonding H H H C C O H H H Least volatile H H H O C C H H H forming between the 2 ethanol molecules given. Conclusion/Explanation/Analysis: Why did the three liquids behave as they did? Be specific. Water Ethanol Hexane CH110 Lab 7. Organic Compounds (W14) 81 Water Ethanol Hexane An Alcohol A Hydrocarbon B. Odor Explain the correlation between volatility and odor Ethanol Hexane An Alcohol A Hydrocarbon C. Solubility And D. Density Physical Properties Results Summary: _____1.As a general rule, hydrocarbons are _____ than water. A. more volatile B. less volatile C. there is no general rule _____2.As a general rule, hydrocarbons are _____ in water and _____in other hydrocarbons. A. soluble, soluble C. insoluble, soluble B. insoluble, insoluble D. soluble, insoluble _____3.As a general rule, most hydrocarbons are _____ than water. A. more dense B. less dense C. there is no general rule _____4.Ethanol is ___________________in water ______________. A. soluble, because the OH is polar. B. insoluble, because it is a mostly hydrocarbon. II. CHEMICAL REACTIVITY: Ethanol Hexane Toluene An Alcohol An Alkane An Aromatic A. Combustion Chemical Reactivity Results Summary: _____5.Which of the following generally give the most soot when burned? A. Alcohols B. Alkanes C. Aromatics _____6.The black soot that is given off when certain hydrocarbons are burned is due to ___ A. impurities that were present in the original sample. B. elemental carbon. C. a mixture of carbon monoxide and carbon dioxide.. D. none of these. 82 CH110 Lab 7. Organic Compounds (W14) III. MOLECULAR MODELS: NAME __________ Follow the procedures in the lab using the following pictures of molecular models. Red spheres represent oxygen atoms, black spheres represent carbon atoms and white ones represent hydrogen. Short grey pegs are carbon to carbon single bonds, short white pegs are carbon to hydrogen bonds and long grey pegs are carbon to oxygen double bonds. In the space provided on the Report Sheet, give the name of the compound class, draw the full structural formula of the molecule and answer questions asked about each model. No. 1 Side View Top View 1. A. Structure (Complete, not condensed) C. Class_________________________ D. Circle any of the following reactions that can easily be performed on this compound a) Oxidation d) Esterification b) Reduction c) Hydrolysis e) none of these E. IUPAC Name __________________ B. Functional group (Box it) F. Common Name _________________ ____________________________________________________________________ No. 2 Side view Top view 2. A. Structure D. Class _________________________ E. Hydrogen Bond? _______________ F. Water soluble? _________________ B. Polar region (circle) C. Nonpolar region (box) G. Circle any of the following reactions that can easily be performed on this compound a) Oxidation d) Esterification CH110 Lab 7. Organic Compounds (W14) b) Reduction e) none of these c) Hydrolysis 83 ____________________________________________________________________ No. 3 Side view Top view 3. B. Class _________________________ A. Structure C. Acid Hydrolysis products (classes): ____________________________________ No 4 Side view Top view 4. A. Structure B. Class _________________________ C. Water soluble? _________________ D. Common Name _________________ 84 CH110 Lab 7. Organic Compounds (W14) No 5 Side view Top view 5. A. Structure B. Class _________________________ C. Acidic Hydrogen (circle) D. Strong acid, Weak acid, Neutral? E. Water Soluble? __________________ F. IUPAC Name __________________ G. Equation for Ionization in water No. 6 6. A. Structure Side view Top view B. Class _________________________ C. Circle any of the following reactions that can easily be performed on this compound a) Oxidation c) Hydrolysis e) Rxn with Alcohols b) Reduction d) Esterification e) none of these D. Water Soluble? __________________ E. IUPAC Name __________________ CH110 Lab 7. Organic Compounds (W14) 85 LAB 7. ORGANIC COMPOUNDS: RELATED EXERCISES: NAME_____________ 1. Write balanced chemical equations to represent the following reactions: A. Combustion of Ethanol: (Use structures not formulas for ethanol) B. Combustion of Hexane: (Use structures not formulas for hexane) 2. Name the class of compound associated with each of the following: A. An Anesthetic _____________________________ B. Fragrances _____________________________ C. Distilled Spirits _____________________________ D. Vinegar _____________________________ 3. You are on a chemical scavenger hunt. As a minimum you need to find an ester, a carboxylic acid, and an alcohol. Go to the kitchen, bathroom, medicine cabinet, garage, grocery store etc. and find three different items that contain the functional groups on the label. List your findings below. Functional Group Product Chemical Name on the Label Ester Carboxylic Acid Alcohol 86 CH110 Lab 7. Organic Compounds (W14)