The Hydroxyl Group: Reactions of Alcohols and Phenols Alcohols and Phenols | CHEM 321, Study notes of Organic Chemistry

Download The Hydroxyl Group: Reactions of Alcohols and Phenols Alcohols and Phenols | CHEM 321 and more Study notes Organic Chemistry in PDF only on Docsity! 1 Solubility in Water 2 Reaction with Sodium The Hydroxyl Group: Reactions of Alcohols and Phenols Alcohols and phenols are organic analogs of water, HOH, in which one hydrogen is replaced by an aliphatic (R—OH) group in the alcohols and by an aromatic (Ar—OH) group in the phenols. The following tests and experi- ments illustrate some properties and reactions of alcohols and phenols. Alcohols and phenols, like water, form strong intermolecular hydrogen bonds: R R A \ \ A O— H----0O—H and O—H----O--H The lewer-molecular-weight alcohols can readily replace water molecules in the hydrogen-bonded network of water. aA R H \ \ \ O— H-~--O—H--~-0-H This hydrogen bonding accounts for he solubility of many alcohols in water. In this part of this experiment, you will test the solubility of several alcohols in water. Procedure In separate test mbes, place 0.5 mL of each of the following alcohcls: ethanol, 1-butanol, 2-methyl-2-propanol, i-hexanol, cyclohexanol, and ethylene glycol. Add 2 mL of water to each test tube, mix, and observe. Record your results for each alcohol on the report sheet.as very soluble, moderately soluble, slightly soluble, or insoluble. Just as with water, the hydrogen atom of the hydroxyl group in alcohols and phenols can be replaced by sodium. 2 HOH + 2Na‘ An <— 2a OH + Hat N 27” sedis bydrozide \ 2 ROH +2Nae ——>%e onatoR + Hot ae todium alkoxide The evolution of hydrogett can be taken‘as evidence for the presence of a hydroxy! group, or other acidic group, in the ‘molecule. Metal alkoxides (like metal hydroxides) are strong bases. : CAUTION : 3 The Lucas Test In this expeciment you will observe the relative reactivity of several alcohola toward * godium, Be extremely careful when handling sodium, Be sire that all your test tubes are clean and dry.* : Sodium: redets violently with water. Never dispose of sodium in the sink. When you havé\completed all your observations, add sufficient methanol to each tube to react completely with any wireacted sodium metal. Only when all the sodiurh, has reacted may y; a discard the contents of each tube in a waste bottle) provided by we instructor. Procedure In separate, dry test tubes, place 2 ml of each of the following alcchols: methanol, 1- -butanal\g- -betanol, and 2-methyl-2-propanol In a fifth test tube, place 2 mL of hexane Xs a comparison control. Using a tweezers (do net hb ‘dle* ‘sodium metal with your fingers), add one smau piece (a sphere 2 mm ir’ diametéxor a cube 2 mm on an edge) of sodium metal to each tube, and note, the result In Same cases, it may be necessary to heat . the mube over a steam bedi i initiate reactién. Record your results, To the methanol m5 /onty, after all the sGdjum has dissolved, add a few drops of phenolphiheléi in indicator solution (this indicator is colorless in acid, pink in bese). Recor your result. Waste Dispose” When you have finished the tests, ae ely add 1 mL of methanol to’ each tube to destroy the excess sodium. Wien nO more so- dium can be observed, pour the contents of the tubes into a waste bottle for organic solvents, provided by your instructor. Alcohols are classified as primary, secondary, or tertiary, depending on whether the hydroxyl-bearing carbon is bound to one, two, or three carbon atoms. When treated with a particular reagent, alcohols may differ in the rates at which they react, or indeed even in the type of product obtained, depending on the class to which they belong. Tests that distinguish among the three classes can be useful in determining the structure of an unknown alcohol. H H R n—b-ox n—b-on n—b—on x b A pemary secondary terdary The Lucas reagent is a solution of zinc chloride in concemtrated hydro- chloric acid. The Lucas test is based on the different rates at which primary, secondary, and tertiary zlcohcls are converted to chlorides with this reagent. ZaQh ROH +HQ ————} R~-C!l + H—-OH The lower alcohols ali dissolve in the reagent to form oxonium salts. "AU xcobols to be tetted should be previeudly dried over molecnlar siever, a The Hydroxyl Group: Solubility in Water Reaction with Sodium The Lucas Test MAME SECTION Report Compound Swructure Ethanol 1-Butanol 2-Methy!-2-propanol 1-Hexanol Cyclohexmol Ethylene glycol Compound Structure Methanol 1-Butanol 2-Butanol 2-Methyl-2-proparol Hexane control Addition of phenolphthzlein to the methanol solution: DATE Solubility in warer Observation Compound Structure 1-Butanol 2-Butanol Cyclohexanol 2-Methyl-2-prepanol Consol Tine for Reaction  Esters Ethanol: Isopentyl! alcohot Compound Structure Acidity of YHetsset Phenols Phenol p-Chlorophenol Compound Reaction of Phenol Phenols and Enols with Resorcinol Ferric Chloride 2,4-Pentanedione 2-Propanol Control Solubilizy Water NaOH Solution Stracture Questions 1. What general conclusions can you draw about the solubility of alcohols in ‘water on the basis of your results in Sec. 17 2. Which is less soluble in water, 1-pentanol or i-heptanoi? Explain. 3. Write an <quation for the reaction of methanol with sodium. 4, What experimental evidence did you observe for the products of the reac- tion of methanol with sodium? 5. What would you expect to happen if sodium methoxide were added to water? Write the equation. 6. Write am equation for the reaction of 2-butanol with the Lucas reagent 7. What would be the result of treating each of the follawing compounds with the Lucas reagent? Explain. a. 2-Methyl-1-propanol b. Cyclopentanol e 1-Methylcyclopentanal 9. Describe the odor of the product derived from mixing isopentyl alcohol and acetic acid (Sec. 5), and write the equation for its formation.