Fractionating-column packing, glass helices

Separation of the hexachlorodisiloxane (b.p. 137°) from unreacted silicon tetrachloride is accomplished by distillation. A 40-cm. fractionating column packed with glass helixes and provided with a heating jacket is suitable. The distillation is started cautiously since much dissolved chlorine is expelled initially. Care. Use a fume hood ) Silicon tetrachloride (b.p. 57°) will pass up the column with little or no heat applied to the jacket. When the bulk of the tetrachloride has passed over, the heat to the flask and the column jacket is increased carefully so that distillation continues steadily. The product passing over at 135 to 138° is collected and redistilled if desired. The recovered silicon tetrachloride may be recirculated. 

To a large bottle are added 116.5 gm (1.0 mole) of 3-chloro-l-hexyne, 20.0 gm (0.20 mole) of cuprous chloride, 16.0 gm (0.30 mole) of ammonium chloride, 10 ml of concentrated hydrochloric acid, 50 ml of water, and 0.6 gm of copper bronze. The bottle is sealed and shaken at room temperature for 14 days. The organic layer is separated, dried over potassium carbonate, and fractionally distilled through a glass-helix-packed column to afford 61.0 gm (52%) of nearly pure l-chloro-l,2-hexadiene, b.p. 54°-57°C (50 mm), p5 1.4567-1.4680, 9.3 gm (8%) of 3-chloro-l-hexyne, and some polymeric material. Shorter periods of reaction give lower yields. The product is purified as described for bromopropadiene. 

To a large bottle are added 470.0 gm (5.6 moles) of 2-methyl-3-butyne-2-ol, 1000 ml of 48 % technical grade hydrobromic acid, 200.0 gm (2.04 moles) of ammonium bromide, and 70.0 gm (0.71 mole) of cuprous chloride. The bottle is sealed, shaken at room temperature for 4J hr, opened, and the organic layer is separated. The organic layer is washed twice with sodium bicarbonate solution, once with a saturated sodium bisulfite solution, dried over calcium chloride, and fractionally distilled through a glass-helix-packed column to afford 500 gm (61 %) of almost pure product (ir 1956 cm-1 allene), b.p. 34°C (18 mm), d5 1.5163. The ir showed that the product contained a trace of l-bromo-3-methyl-1,3-butadiene (1580 and 1620 cm-1). 

This consists mostly of acetic acid, acetic anhydride, and some tetrahydrofurfuryl acetate. By fractional distillation through a 15-in. glass-helix-packed column, in. in diameter, about 700 g. of acetic acid boUing at 117-125° and about 1075 g. of acetic anhydride boiling at 137-142° can be recovered. 

Shake suberone with aqueous KMn04 to remove material absorbing around 230-240nm, then dry it with Linde type 13X molecular sieves and fractionally distil it through a glass helix packed column. [Blicke et al. 7 Am Chem Soc 74 2924 1952, Dauben et al. Org Synth CoU Vol IV 221, 229 1963, Beilstein 7 H 13, 7 19,7 n 14,7 in 46,7 IV 39.]... 

The crude sulfur(IV) fluoride that collects in the receiver is distilled into the pot of a dry low-temperature glass fractionating column, for example, one having a rectifying section 12 mm. in diameter and 280 mm. in length packed with -in.-i.d. glass helixes and cooled with solid carbon dioxide... 

NOTE The original procedure [35] calls for the use of a Widmer column for the fractional distillation step. Since this piece of equipment is no longer generally available and discredited by some experts in laboratory fractional distillations, we suggest the use of a single-turn, glass-helix packed distillation column or its equivalent with a total-reflux, partial-take-off distillation head. 

The dried amine is then fractionally distilled through a glass-helix-packed distillation column. The fraction boiling at 76.5°C (742 mm) is collected. Yield 191.7 gm (47% of theory), 1.4008. 

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