Distillation columns Stedman

Methyl trichlorosilane [75-79-6] M 149.5, b 13,7 /101mm, 64.3 /710.8mm, 65.5 /745mm, 66.1 /atm, d 1.263, n 1.4110. If very pure distil before use. Purity checked by Si nmr, 6 in MeCN is 13.14 with respect to Me4Si. Possible contaminants are other silanes which can be removed by fractional distillation through a Stedman column of >72 theoretical plates with total reflux and 0.35% take-off (see p. 441). The apparatus is under N2 at a rate of 12 bubbles/min fed into the line using an Hg manometer to control the pressure. Sensitive to H2O. [J Am Chem Soc 73 4252 7957 J Org Chem 48 3667 7955.]... 

Stedman Packing Available in metal only, usually used in batch and continuous distillation in small diameter columns not exceeding 24-inches dia. High fractionation ability per unit height, best suited for laboratory work. Conical and triangular types available. Not much industrial data available. 

Methyl dichlorosilane [75-54-7] M 115.0, m -92.5°, b 41°/748mm, 40.9°/760mm, 40-45°/atm, d j l.105. Impurities are generally other chloromethyl silanes. Distilled through a conventional Stedman column of 20 theoretical plates or more. It should be protected from H2O by storing over P2O5. [fl 52 695 1919 JACS 68 9621946]. 

Likely impurities are other chlorinated methylsilanes, and tetrachlorosilane (b 57.6°/atm), some of which can form azeotropes. To avoid the latter very efficient fractional distillation is required. It has been fractionated through a 12 plate glass helices packed column with only the heart-cut material used. It has also been fractionated through a 90cm, 19mm diameter Stedman column. Also purified by redistilling from CaH2 before use. [/ACS 70, 4254, 4258 7948 JOC 23 50 7958],... 

Acetonitrile. CH3CN, b.p. 81.6° [1, 7, before a-Acetoxyacrylonitrile]. Aprotic. water-miscible Diels-Alder solvent (1, 239). Supplier of pure solvent. 1, 1110. For polara-graphic use. Moe1 notes that the main impurity is acrylonitrile, which differs from it in b.p. by only 4.2°, and recommends separation by distillation of the ternary and secondary azeotropes which the two liquids form with ethanol and with water. Ethanol (95%) is added to practical acetonitrile and the mixture is distilled through an H. Stedman column of 60-65 theoretical plates. The purified material is suitable also for U V spectroscopy. 

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