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 Purification of 1-Propanol

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PostSubject: Purification of 1-Propanol   Tue Aug 02, 2011 8:48 am

The main impurities in 1-Propanol (CAS NO. 71-23-Cool are usually water and 2-propen- l-ol, reflecting the commercial production by hydration of propene. Water can be removed by azeotropic distn either directly (azeotrope contains 28% water) or by using a ternary system, e.g. by adding benzene. Alternatively, for gross amounts of water, refluxing over CaO for several hours is suitable, followed by distn and a further drying. To obtain more nearly anhydrous alcohol, suitable drying agents are firstly NaOH, CaSO4 or K2CO3, then CaH2, aluminium amalgam, magnesium activated with iodine, or a small amount of sodium. Alternatively, the alcohol can be refluxed with n-propylsuccinate or phthalate in a method similar to the one described under EtOH. Allyl alcohol is removed by adding bromine (15mL/L) and then fractionally distilling from a small amount of K2CO3. Propionaldehyde, also formed in the bromination, is removed as the 2,4-dinitrophenylhydrazone. 1-Propanol can be dried down to 20ppm of water by passage through a column of pre-dried molecular sieves (type 3 or 4A, heated for 3h at 300 °C) in a current of nitrogen. Distn from sulfanilic or tartaric acids removes impurities. Albrecht obtained spectroscopically pure material by heating with charcoal to 50-60 °C, filtering and adding 2,4-dinitrophenylhydrazine and a few drops of conc H2SO4. After standing for several hours, the mixture was cooled to 0 °C, filtered and vac distd. Gold and Satchell heated 1-Propanol with 3-nitrophthalic anhydride at 76-110 °C for 15h, then recrystd the resulting ester from H2O, benzene/pet ether (b 100-120 °C)(3:1), and benzene. The ester was hydrolysed under reflux with aq 7.5M NaOH for 45min under nitrogen, followed by distn (also under nitrogen). The fraction (b 87-92 °C) was dried with K2CO3 and stirred under reduced pressure in the dark over 2,4-dinitrophenylhydrazine, then freshly distilled.

1-Propanol is also purified by adding 2g NaBH4 to 1.5L alcohol, gently bubbling with argon and refluxing for lday at 50 °C. Then added 2g of freshly cut sodium (washed with propanol) and refluxed for one day. Distd, taking the middle fraction.
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