3015 Synthesis of iodocyclohexane from cyclohexane and iodoform

Transcription

1 5 Synthesis of iodocyclohexane from cyclohexane and iodoform + CHI NaOH I C 6 H (8.) CHI (9.7) (.) C 6 H I (.) Literature P. R. Schreiner, O. Lauenstein, E. D. Butova, and A. A. Fokin, Angew. Chem. 999,, ; Angew. Chem. Int. Ed. Engl. 999, 8, P. R. Schreiner, O. Lauenstein, E. D. Butova, P. A. Cunchenko, I. V. Kolomistin, A. Wittkopp, G. Feder, A. A. Fokin, Chem. Eur. J.,, 7, 997 Classification Reaction types and substance classes: iodination, radical reaction alkane, iodoalkane Work methods: working with light exclusion, stirring with magnetic stir bar, shaking out, extracting, filtering, evaporating with rotary evaporator, distilling under reduced pressure Instruction (batch scale 5 mmol) Equipment 5 ml round bottom flask, magnetic stirrer, magnetic stir bar, distillation apparatus, vacuum pump, rotary evaporator, oil bath Substances iodoform (triiodomethane) (mp C) sodium hydroxide 8 ml, g,.66 mol, 9.7 g (5. mmol) 8. g (76 mmol) 5 ml Reaction 8 ml ( g,.66 mol) cyclohexane, 8. g (76 mmol) finely powdered NaOH and 9.7 g (5. mmol) iodoform are filled into a 5 ml round bottom flask equipped with an efficient magnetic stir bar. The flask is locked with a glass stopper and is wrapped with tin foil in order

2 to protect the content from light effect. The mixture is stirred for 8 hours at topmost-possible stirring speed at room temperature. Work up The mixture is filtered and the solid residue five times extracted with ml cyclohexane each. From the organic phases the solvent is removed with a rotary evaporator under slightly reduced pressure ( hpa). A greasy liquid remains as crude product. Crude yield: 8.9 g The crude product is distilled at reduced pressure. Yield: 5.8 g; (7.6 mmol, 55%); bp 7 C ( hpa), clear, easily yellow, viscous liquid. Waste management Waste disposal Waste filter residue evaporated cyclohexane distillation residue Disposal solid waste, free from mercury organic solvents, halogen free dissolve in a small amount of acetone, then: organic solvents, containing halogen Comments Since the reaction mixture is heterogeneous, the reaction speed depends strongly on the stirring speed. Time 5 hours, with 8 hours of stirring Break Before the work up Degree of difficulty Easy Instruction (batch scale mmol) Equipment ml round bottom flask, magnetic stirrer, magnetic stir bar, microdistillation apparatus, vacuum pump, rotary evaporator, oil bath Substances iodoform (triiodomethane) (mp. C) sodium hydroxide 6 ml, (6.8 g, 556 mmol).9 g (. mmol) 5.65 g ( mmol) 5 ml

3 Reaction 8 ml (6.8 g, 556 mmol) cyclohexane, 5.65 g ( mmol) finely powdered NaOH and.9g (. mmol) iodoform are filled into a ml round bottom flask equipped with an efficient magnetic stir bar. The flask is locked with a glass stopper and is wrapped with tin foil in order to protect the content from light effect. The mixture is stirred for 8 hours with topmostpossible stirring speed at room temperature. Work up The mixture is filtered and the solid residue three times extracted with ml cyclohexane each. From the organic phases the solvent is removed with a rotary evaporator under slightly reduced pressure ( hpa). A greasy liquid remains as crude product. Crude yield:.9 g The crude product is distilled in a microdistillation apparatus at reduced pressure. Yield:. g (5.7 mmol, 57%, bp 7 C ( hpa), clear, easily yellow, viscous liquid. Waste management Waste disposal Waste filter residue abrotiertes cyclohexane distillation residue Disposal solid waste, free from mercury organic solvents, halogen free dissolve in a small amount of acetone, then: organic solvents, containing halogen Comments Since the reaction mixture is heterogeneous, the reaction speed depends strongly on the Rührgeschwindigkeit. Time 5 hours, with 8 hours of stirring Break Before the work up Degree of difficulty Easy

4 Analytics GC Sample preparation: One drop of the compound is dissolved in ml tert-butyl methyl ether, µl is injected. GC conditions: column: Macherey und Nagel, SE-5, 6-MN-75-9, 5 m, ID. mm, DF.5 µm inlet: Gerstel KAS, injector 5 C; split injection: :, injected volume µl carrier gas: nitrogen, pre-column pressure 6 kpa, flow rate. ml/min oven: 8 C ( min), 5 C/min, 5 C ( min) detector: FID, 75 C Percent concentration was calculated from peak areas. GC of the crude product GC of the pure product Retention time (min) Substance Peak area % Crude product Pure product 9. product (iodocyclohexane) unidentified (probably thermic 5 6 others unidentified decomposition products).5

5 H NMR spectrum of the crude product (5 MHz, CDCl ) H NMR spectrum of the pure product (5 MHz, CDCl ) δ (ppm) Multiplicity Number of H Assignment.. M CH M CH M CH. -.8 M CH. -.8 M CHI 7.6 solvent The signal at.87 ppm in the spectrum of the crude product originates from the diiodmethane. 5

6 C NMR spectrum of the crude product (5 MHz, CDCl ) C NMR spectrum of the pure product (5 MHz, CDCl ) δ (ppm) Assignment 5. C- 7. C-, C-5.9 C- 9.6 C-, C solvent 5 6 I The signal at ppm in the spectrum of the crude product originates from the diiodmethane. 6

7 IR spectrum of the crude product (film) IR spectrum of the pure product (film) (cm - ) Assignment 9, 875, 85, 89 C-H-valence, alkane 57 C-I-valence 7