sium dihydrogen phosphate fixing solution to illustrate its applicability as an ammonia fixing agent, while the other distillations employed a 1000p.p.m. boric acid fixing solution. The per cent relative standard deviation decreases as the concentration of ammonia increases and indicates satisfactory reproducibility.
Thc kinetics of the desulfonation of benzenesulfonic and the isomeric toluenesulfonic acids have been studied at 120-155" in 65-85 wt-%, sulfuric acid with the aid of an inert gas (nitrogen) stripping technique. All reactions were found to be of the first order with respect to the initial sulfonic acid. At high temperatures and/or high sulfuric acid concentrations substantial isomerisation of the toluenesulfonic acids took place, especially at low nitrogen flow rates.The rate-constants of the desulfonation step proper -i.e. the rate-constants corrected for resulfonation -increase with increasing acid concentration and temperature. The dependence of the rate of desulfonation on acidity is compatible with the sulfonation mechanism recently proposed by K o r f and Cerfr,nfain 4n, if the sulfonate anion is supposed to be the active substrate species in the desulfonation reaction.Partial rate-factors for protodesulfonation of the toluenesulfonic acids and the trrr-butylbenzenesulfonic acids have been calculated. For a given alkyl substituentf;, : f,, > f,,&. The protodesulfonation obeys the Selectivity Relationship. It is, therefore, suggested that the protodesulfonation of arenesulfonic acids in aqueous sulfuric acid proceeds viu a Wheland-type intermediate.
The development of a pilot plant process to prepare the
spirocyclic piperidine (2) from the tetrahydropyridine (4) via
a radical cyclisation reaction is described. The pilot plant
process involves the use of a catalytic amount of tributyltin
hydride (0.14 equiv) generated in situ by the reaction of
tributyltin chloride with sodium borohydride (1.1 equiv) in
2-propanol/ethanol containing azo-bis(isobutyronitrile) (AIBN).
Initial laboratory conditions are described as well as the changes
made on transfer to the pilot plant. Measurement of the levels
of residual amounts of tin in the batches of (2) produced are
reported.
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