Synthesis of 1- Bromobutane An SN2 Reaction
Theory: One of the methods of preparing alkyl halides is via the nucleophilic substitution reactions of alcohols. Alcohols are inexpensive materials and easy to maintain. However, they are a poor leaving group the OH group is a problem in nucleophilic substitution, this problem is fixed by converting the alcohol into H2O. Objective: The objective of this lab is to observe the synthesis of 1-bromobutane in an SN2 reaction, to see how a primary alky halide reacts with an alcohol. Reagents:
Reagents | Physical properties |
Sodium bromide | Molecular formula: NaBrMolar mass: 102.894 g/molAppearance: White powderDensity: 3.21 g/cm3 (anhydrous)2.18 g/cm3 (dihydrate)Melting point747 °C (anhydrous)36 °C (dihydrate)Boiling point1396 °CSolubility in water: 90.5 g/100 mL (20 °C) 121.0 g/100 mL (100 °C)Solubility in methanol16.7 g/100mL| 1-butanol| Molecular formula:C4H10OMolar mass:74.12 g mol−1Appearance: Colourless liquidDensity: 0.81 g cm-3Melting point: −90 °C, 183 K, -130 °FBoiling point: 118 °C, 391 K, 244 °FSolubility in water73 g L-1 at 25°C| NaOH| Molecular formula: NaOHMolar mass: 39.9971 g mol-1Appearance: White, waxy, opaque crystalsOdor odorlessDensity: 2.13 g/cm3Melting point: 318 °C, 591 K, 604 °FBoiling point: 1388 °C, 1661 K, 2530 °FSolubility in water111 g/100 mL (at 20 °C)Solubility in methanol23.8 g/100 mLSolubility in ethanol<<13.9 g/100 mL| Saturated NaCl| Molecular formula: NaClMolar mass: 58.44 g mol−1Appearance: Colorless crystalsOdor OdorlessDensity: 2.165 g cm−3Melting point: 801 °C, 1074 K, 1474 °FBoiling point: 1413 °C, 1686 K, 2575 °FSolubility in water: 359 g L−1Solubility in ammonia: 21.5 g L−1Solubility in methanol: 14.9 g L−1| Anhydrous Na2SO4| Molecular formula: Na2SO4Molar mass: 142.04 g/mol (anhydrous)322.20 g/mol (decahydrate)Appearance: white crystalline solidHygroscopic Odor: odorlessDensity: 2.664 g/cm3 (anhydrous)1.464 g/cm3 (decahydrate)Melting point: 884 °C (anhydrous)32.38 °C (decahydrate)Boiling point: 1429 °C (anhydrous)Solubility in wateranhydrous:4.76 g/100 mL (0 °C)42.7 g/100 mL (100 °C)heptahydrate:19.5 g/100 mL (0 °C)44 g/100 mL (20 °C)Solubility insoluble in ethanolsoluble in glycerol and hydrogen iodide|
Procedure: First 10.3 grams of sodium bromide was placed into 100-mL of a round-bottomed flask and about 10 mL of water and 7.5g of 1-butonaol was added. The contents were mixed in a flask thoroughly by swirling, and then cooling the flask in an ice water bath. The flask was then removed from the ice water bath and several boiling chips were added. A reflux condenser was then attached to gently warm the flask until all the salts dissolved, and then heated under gentle reflux, a noticeable reaction occurred of 2 layers and the flask was continued heated for 45 minutes. The flask was then equipped for simple distillation, and the mixture was distilled rapidly until all the distillate was collected, the distillation was continued until the distillate was clear. The distillate was transferred to a seperatory funnel and about 10 mL of water was added. The funnel was shook gently while venting. The layers were then separated and the organic layer was observed. The organic layer was then washed with 2 M of aqueous NaOH solution and then with about 10 mL of saturated NaCl solution. The cloudy 1-bromobutane layer was then transferred to a 25-mL Erlenmeyer flask and dried over anhydrous. The flask was swirled occasionally for 10-15 minutes until the crude 1-bromobutane is clear. The crude 1-bromobutane was then transferred without the drying agent to a clean dry 25-mL round bottomed flask. Three boiling chips were then added and the flask was equipped for simple distillation, and carefully distilled. The weight and boiling point was then obtained of the product and recorded.
Boling point 1-bromobutane | 97oC|
Starting weight 1-butonaol | 7.5g|