Preparation of Cyclohexanol

1 CHY 224 REPORT FORM  PREPARATION OF CYCLOHEXANOL  NAME: ______________________________________________________________________ Partner: _____________________________________________________________________ Day: ______________ Time: ______________ Room: ______________ Please type the answers to the following questions. 1. Create a table to show the reactants, and products for the reaction that you performed. Please be sure to include the pertinent physical data (citing your sources). This table should include the observed boiling point ranges, literature boiling points, masses/volumes (and molar amounts) of each of the reactants, and products. (4 marks) 2. Define the term “azeotrope” and which azeotrope was formed in this experiment? (1 mark) 3. What is the solid that may form in the condenser on the second week of this synthesis? Why could it form? (1 mark) 4. Create a table showing the functional groups for cyclohexanol showing the expected region for each infrared peak. Include the actual peaks from your spectra that you are assigning to each functional group. Are there any cyclohexene peaks visible? Where would you expect to see IR evidence of cyclohexene in your final product? (4 marks) 5. Calculate the percent yield for the synthesis of cyclohexanol. Please be sure to show all of your calculations. (2 marks) 6. Show the calculation for the temperature correction of refractive index using your experimental data. Comment on the purity of your product based upon the refractive index measurement. (2 marks) 7. Write a formal discussion for this experiment. Be sure to include comments on the important experimental data, reasonable sources of error, and comment on the purity of your prepared cyclohexanol. Compare your actual yield versus the theoretical yield. (6 marks) Agilent Plot Name Unknown 2 Agilent Resolutions Pro A bs or ba nc e 100 90 80 70 60 50 40 Unknown 2 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 Wavenumber CYCLOHEXANOL EXPERIMENT #4 PREPARATION OF CYCLOHEXANOL LEARNING OBJECTIVES: ❖ To be able to develop a protocol for a reaction without step by step instructions ❖ Introduction to proposal creation. Increase written ability ❖ Produce, purify, and then test the purity of a marketable product Introduction It has often been said that necessity is the mother of invention. For this experiment you need 20 grams of cyclohexanol. When you go to the storeroom, the bottle is empty and when you try to order it, you find that it is on backorder. Your research needs cyclohexanol to progress, and you cannot wait. Therefore you need to make the required 20 grams. You have both cyclohexene and cyclohexanone available. You must choose which route that you are going to use to make the cyclohexanol. You will need to create a proposal showing the procedure that you will follow. The proposal must show justifications for the choices that you made with respect to the procedure for making the cyclohexanol. Please determine the cost of making the cyclohexanol. Be sure to include the cost of all reagents, and factor in your time. You can assume that we have the basic organic glassware, so these do not need to be part of the cost analysis. Be sure to include all pertinent physical data about your reactants and product. You will be working with your partner in the lab, but you need to produce your own proposal. Please discuss with your partner how you intend to make the cyclohexanol but please ensure that you do not commit academic misconduct by copying from each other. CYCLOHEXANOL EXPERIMENT #4 CYCLOHEXENE OPTION: HYDRATION OF AN ALKENE This is an acid catalysed addition. The acid that would be available would be sulphuric acid. Please be mindful that this is an exothermic reaction and that cyclohexene is volatile. Adding water would be a good source of hydroxyl groups. Overall Reaction Cyclohexene Cyclohexanol Initially, cyclohexene is insoluble in the water-acid solution and appears as a two-phase mixture. Cyclohexene will react with water and also with sulfuric acid to form two products: protonated cyclohexanol and cyclohexyl hydrogen sulfate. Both of these products are soluble in the water-acid solution, therefore, when the original two-phase mixture becomes homogeneous, the reaction is complete. In practice, the degree of homogeneity is difficult to distinguish because of darkening of the reaction mixture from cationic polymerization of cyclohexene. Cyclohexanol is isolated from the reaction mixture by dilution with water followed by steam distillation. When the water is added, a two-phase system results: an upper layer of cyclohexanol and a lower layer of aqueous acid. When this mixture is heated, the cyclohexyl hydrogen sulfate by-product is converted to protonated cyclohexanol that is in equilibrium with cyclohexanol. Steam distillation separates the organic compounds from the sulfuric acid solution. The distillate consists primarily of cyclohexanol and water plus a small amount of cyclohexene. Because cyclohexanol and water form an azeotrope that boils at 98°C, the bulk of the material distills at this temperature. An azeotrope is a mixture of two or three compounds which, when distilled, exhibit a fixed boiling point, like that of a pure compound. Salting out is a technique commonly used in extractions; its main purpose is to improve the yield of the product. Salting out is done by adding enough salt to the aqueous phase to make it a saturated solution. Salt helps to remove the organic compound from the aqueous phase by reducing the solubility of the organic compound in water, forcing a transfer of the organic compound out of the aqueous phase and into the organic phase. This step is followed by the separation of the organic phase from the aqueous phase. As a further precaution against mechanical loss (droplets clinging to the separatory funnel, etc.), diethyl ether is used to extract the cyclohexanol from the salt-water mixture. After separation, the organic layer is dried prior to distillation. Anhydrous magnesium sulfate is a suitable drying agent; however, anhydrous potassium carbonate is the agent of choice because it will neutralize any trace of acid that may have been carried through the work-up procedure. In the final distillation, a trace of acid would cause dehydration of the cyclohexanol. H2SO4 H2O OH CYCLOHEXANOL EXPERIMENT #4 Tips - 14 mL of sulphuric acid would be a suitable volume for catalysis. - Ice will be available to keep your reaction flask cool - You should vigorously shake the reaction mixture for at least 30 minutes to ensure the reaction proceeds towards the products. Vent periodically to prevent pressure build up. - Please ensure that boiling chips and vacuum grease are used when performing a distillation, and using ground glass - The amount of salt required to make a saturated solution can be calculated in advance. - It would be good to take note of any boiling points that were observed in both of the distillations - Parafilm will be available to store your sample after salting it out. This would be a good place to break after the first lab session. - Diethyl ether will be available on the second lab session for extractions. - Potassium carbonate will also be available on the second lab session to dry your sample and neutralize any excess acid. - After your final distillation, be sure to measure the quantity that you actually made (compare this to the amount theoretically possible). Do not boil to dryness. - Also be sure to test the purity of your sample (indicate in your proposal how you intend to do this). CYCLOHEXANOL EXPERIMENT #4 CYCLOHEXANONE OPTION: REDUCTION OF A KETONE Reducing cyclohexanone to cyclohexanol is a second option that you have. The reduction reaction can be accomplished several ways but there are many factors to take into consideration in choosing which is best suited for your purpose. Metal hydrides of the Group III elements were first discovered in 1943, and were found to be very useful reducing agents. Lithium aluminum hydride, LiAlH4, reduces many compounds containing carbonyl groups, such as aldehydes, ketones, carboxylic acids, esters and amides. Sodium borohydride, NaBH4, is less reactive and therefore can only reduce aldehydes and ketones to primary and secondary alcohols. Sodium borohydride is mainly used in organic synthesis, while lithium aluminum hydride is used in organic synthesis and other applications. Before these metal hydrides were known, carbonyl groups were reduced to alcohols by treatment with hydrogen (H2) and sodium metal. All the metal hydrides work by providing a hydride (H:-) that will act as a nucleophile to attack the electrophilic carbonyl carbon; however, no free hydride ions are generated in solution. Kinetic studies indicate that a solvent molecule bonds to the boron atom while hydride is being transferred to the carbonyl compound. Another solvent molecule (if the solvent is protic) provides the proton for the carbonyl oxygen that has the electrons from the broken π-bond. Therefore, while the overall reduction of carbonyl requires two hydrogens, only one of these comes from the reagent (that on carbon); the other hydrogen comes from the protic solvent. Sodium Borohydride and Lithium Aluminum Hydride Reduction Reaction Cyclohexanone Cyclohexanol In this equation 1 mole of sodium borohydride or lithium aluminum hydride can reduce