Organic chemistry practical course Autumn semester 2008 Synthesis of tert-butyl chloride 26.10.2008 Synthesis of tert-butyl chloride Natalja Früh, 07-922-404, D-CHAB, fruehn@student.ethz.ch Assistant: Alexey Federov 1 Organic chemistry practical course Autumn semester 2008 Synthesis of tert-butyl chloride 26.10.2008 1. Theory 1.1. Reaction 1.2. Mechanism RDS The mechanism for the synthesis of tert-butyl chloride is a nucleophilic substitution of type SN1 of tert-butanol with hydrochloric acid (HCl). A nucleophilic substitution of type SN2 doesn’t occur, because the center is sterically hindered. A side reaction that could occur would be an elimination of type E1 with product isobutene. This side reaction is preferred by high temperature. The second step is the rate-determining step (RDS), in which a carbocation is formed, when the C goes from sp3-hybridization to sp2-hybridization. 2 Organic chemistry practical course Autumn semester 2008 Synthesis of tert-butyl chloride 26.10.2008 2. Procedure 2.1. Experimental setup 2.1.1. Extraction separation funnel organic phase aqueous phase 100 100 mL 75 50 3 Organic chemistry practical course Autumn semester 2008 Synthesis of tert-butyl chloride 26.10.2008 2.1.2. Distillation contact thermometer 30o vigreux column 100 m L in out cooling water 250 m L LaboBib 300 50 © AN AN AUS AUS 1500 100 0 U/min 250 500 o C 200 150 1000 750 4 Organic chemistry practical course Autumn semester 2008 2.2. Synthesis of tert-butyl chloride 26.10.2008 Procedure 20.68g of tert-butanol and 65ml of HCl (37%) are put into a 500ml seperatory funnel and mixed together. After vigorous shaking for about 5 minutes, there are two phases, an organic one and an aqueous one. The aqueous phase is due to the higher density on the bottom and can be discharged. The organic layer (upper) is washed three times with 20ml saturated NaHCO3 to neutralize the remaining HCl and once with 25ml saturated NaCl to fetch the remaining H2O out. Each time the funnel is shaken for short time, the device is opened while the funnel is upside down to let the accumulated gas escape. The organic phase is put into a 100ml round-neck-flask and a spattle of CaCl2 is added to dry. The substance is purified by distillation under atmospheric pressure, as the boiling point of the product is around 51°C. The measured vapor temperature is between 47°C to 50°C as expected. Important for the distillation is, that the first and the last few drops are collected in a small flask because these drops could be impure and contaminate the product. After the distillation the product is kept in a round-neck-flask closed by a stopper due to the low boiling point. 2.3. Results 2.3.1. Yield Substance Amount [mol] Equivalent/yield tert-butanol HCl (37% / ~ 12M) tert-butyl chloride discarded drops (distillation) 20.68 g 65 ml 15.46 g 0.75 g 0.279 mol 0.8 mol 0.167 mol ~ 0.01 mol 1 eq 3 eq 60% (yield) ~ 3 % (yield) 2.3.2. Refractive index A refractive index of n20D = 1.383 is measured, the literature value of tert-butyl chloride is n20D =1.3856. 5 Organic chemistry practical course Autumn semester 2008 Synthesis of tert-butyl chloride 26.10.2008 2.3.3. Infrared spectrum Literature Measured spectrum Bands [cm-1] 2990 - 2950 1470 1456 1370 1150 809 Interpretation C-H stretching vibration C-H deforming vibration C-C vibration C-Cl stretching vibration 6 Organic chemistry practical course Autumn semester 2008 Synthesis of tert-butyl chloride 26.10.2008 7 Organic chemistry practical course Autumn semester 2008 Synthesis of tert-butyl chloride 26.10.2008 3. Physical and Chemical Properties of Substances tert-butanol C4H10O CAS: 75-65-0 Molecular Weight Density Refractive Index Risk phrases R11 R20 Safety phrases S9 S16 74.122 g/mol d254 0.78 g/cm3 n20D 1.3823 Melting Point Boiling Point 25.5° C 82.8 ° C Highly flammable Harmful by inhalation Keep container in a well-ventilated place Keep away from sources of ignition – no smoking CH Toxicity class 4 MAK 100ml/m3; 300mg/m3 hydrogen chloride (37%) HCl CAS: 7647-01-0/37 Molecular Weight Density Risk phrases R34 R37 Safety phrases S26 HCl S36/37/38 S45 36.461 g/mol d25 1.19 g/ml Melting Point Boiling Point -25° C 85° C Causes burns Irritating to the respiratory system In case of contact with eyes, rinse immediately with plenty of water and seek medical advice Wear suitable protective clothing, gloves and eye/face protection In case of accident or if you feel unwell, seek medical advice immediately (show label where possible) CH Toxicity class 2 MAK 5ml/m3; 7mg/ml3 Sodium hydrogen carbonate NaHCO3 CAS: 144-5-8 Molecular Weight Density Refractive Index 84.007 g/mol d25 2.159 g/cm3 n20D 1.500 Melting Point decomposes around 50° C Safety phrases S24/25 Avoid contact with skin and eyes CH Toxicity class 5 8 Organic chemistry practical course Autumn semester 2008 Sodium chloride NaCl CAS: 7647-14-5 Synthesis of tert-butyl chloride 26.10.2008 Molecular Weight Density 58.442 g/mol d25 2.16 g/cm3 Melting Point Boiling Point Safety phrases S24/25 Avoid contact with skin and eyes 801° C 1413° C NaCl CH Toxicity class non-toxic Calcium chloride CaCl2 CAS: 10043-52-4 CaCl2 tert-butyl chloride C4H9Cl CAS: 507-20-0 Molecular Weight Density Risk phrases R36 Safety phrases S15 S25 Molecular Weight Density Refractive Index Risk phrases R11 Safety phrases S7/99 S16 S29 S33 110.983 g/mol d25 2.15 g/cm3 Melting Point Boiling Point 772° C >1600° C Irritating to eyes Keep away from heat Avoid contact with eyes 92.568 g/mol d15 0.85 g/cm3 n20D 1.3856 Melting Point Boiling Point -25° C 52° C Highly flammable Keep container tightly closed and in a wellventilated place Keep away from sources of ignition – no smoking Do not empty in drains Take precautionary measures against static discharges CH Toxicity class 4 4. Sources Combined Chemical Dictionary, Taylor & Francis Group, 2008 http://ccd.chemnetbase.com/dictionary-search.do?method=view&id=2145609&si= Verein Biologie Studierender, 2008 http://www.vebis.ch AIST, National Institute of Advanced Industrial Science and Technology (Japan), 2008 http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi 9