Todd column

Crotyl bromide [29576-14-5] M 135.0, b 103-105 /740mm, n s 1.4792. Dried with MgS04, CaC03 mixture. Fractionally distd through an all-glass Todd column. [Todd column. A column (which may be a Dufton type, fitted with a Monel metal rod and spiral, or a Hempel type, fitted with glass helices) which is surrounded by an open heating jacket so that the temperature can be adjusted to be close to the distillation temperature (Todd Ind Eng Chem (Anal Ed) 17 175 1945)]. 

Dinitrofluorobenzene (Sanger s reagent) [70-34-8] M 186.1, m 25-27 , b 133 /2mm, 140-141 /5mm, d 1.483. Crystd from ether or EtOH. Vacuum distd through a Todd Column (see p. 174). If it is to be purified by distn in vacuo, the distn unit must be allowed to cool before air is allowed into the apparatus otherwise the residue carbonises spontaneously and an EXPLOSION may occur. The material is a skin irritant and may cause serious dermatitis. 

Steam distd from a soln containing 1-2 equivalents of 20% H2SO4 until about 10% of the base had been carried over with the non-basic impurities, then the acid soln was made alkaline, and the base separated, dried with NaOH and fractionally distd twice. Dried with Na and fractionally distd through a Todd column packed with glass helices (see p. 174). 

Crotyl bromide [29576-14-5] M 135.0, b 103-105°/740mm, CaCO3 mixture. Fractionally distd through an all-glass Todd column. 

It forms a picrate m 149° (from EtOH-pet ether) from which the free base can be recovered using a basic ion exchange resin and can then be distd through a Todd column using an automatic still head which only collects products boiling below 51°/atm. Polymeric materials if present will boil above this temperature. The hydrochloride has m 85-86°. The pKa in 40% EtOH is 5.33. [Roberts and Chambers JACS 73 5030 1951, Jones JOC 9 484 7944 Emmons J A CS 79 6522 1957. ... 

Pyrrolidine [123-75-1] M 71.1, b 87.5-88.5°, d 0.860, n 1.443. Dried with BaO or sodium, then fractionally distd, under nitrogen, through a Todd column packed with glass helices. 

Tin tetramethyl [594-27-4J M 178.8, m 16.5", b 78.3"/740mm. It is purified by fractionation using a Todd column of 35-40 plates at atmospheric pressure. The purity of the fractions can be followed by IR [JACS 77 6486 7955]. It readily dissolves stopcock silicone greases which give bands in the 8-10)1 region. [JACS 76 1169 1954],... 

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