Centrifugal reactor

Plasma Incineration Systems Pyroplasma System Pyrolytic Centrifugal Reactor Pyrolysis... 

A centrifugal reactor suited for handling of low crosslinked gels has been constructed by Birr (27). 

Russell, A. J. and Komives, C., May the centrifugal force be with you A novel centrifugal reactor system is used with reversed micelle-enzyme catalysts to biodegrade organophosphates, CHEMTECH, 26-32, 1994. 

These aspects clearly indicate that deprotections on polymer phase never should be considered standardized reactions which can be simply progranuned in a uniform manner [117]. From the author s point of view we can only meet this problem by continuous recording of each deprotection reaction, to monitor its completion and to gather additional information on the solvation behavior of the growing peptide on polymer. As shown in the paragraph after next, this is realized in the use of a,a-dimethyl-3,5-di-methoxybenzyloxycarbonyl (Ddz) protected amino acids on polymer phase with the aid of a centrifugal reactor, which will be explained in Sect. 4.1.3. 

By the aid of a modified peptide synthesizer solutions of two moles of Boc- or Ddz-amino acid salts (sodium- or triethylammonium form) in tetrahydrofuran or dichloro-methane at —40 °C are mixed for 5 minutes with one mole of phosgene in the same solvent at —40 °C, controlled by the punched tape program of the synthesizer (Fig. 44). The solution of the symmetric anhydride is added at —40 C to the gel polymer, which is contained in the centrifugal reactor (see p. 75) and is allowed to warm up to the cooling water temperature level (9—13 C) of the reactor during the peptide synthesis period of 30 minutes. Since the mode of action of the centrifugal reactor renders it possible to perfuse an external IR flow cell with the reaction solution, we are in a position to monitor directly the quality of the symmetric anhydride and its consumption, watching the characteristic absorptions on 1,830 and 1,760 cm [71]. In several cases the symmetric anhydrides were isolated in crystalline or solid form for characterization (Table 6). 

To date there have been hardly any experiences concerning the efficiency of ammo-nolytic detachment of peptides Unked to the support by phenacyl groupings. For analytical purposes, in our laboratory we detected, by the aid of our photometric synthesis control system, the release of hpophilic peptide amides within 24 hours of ammonolysis. The reagent we are utilizing is 10% (w) ammonia in dioxane/methanol 9 1 (v v), with renewal of the mixture delivered to the centrifugal reactor every 2 hours. It should be recalled, however, that in most of the cases when peptide amides are to be built up, the target sequences are synthesized on a benzhydrylamine support [171], which by HF-cleavage directly releases the entirely deprotected amide (see p. 64). 

Fig. 60. The mode of operation of the centrifugal reactor. (A) Filling (B) Start of rotation (C) Internal and external circulation of reaction liquids caused by centrifugal forces (D) Draining by spinning off (c) Flow cell d Drain line...

In addition to the intense internal current of liquid continuously penetrating the polymer support inside the spinning rotor, an external flow can be diverted since the mode of action in the vessel is comparable to a rotary pump. In this way external flow cells can be circulated with reaction solutions from the centrifugal reactor without any additional pump. Hereby, the alterations of concentrations in the circulating solutions caused by consumption of reagents or liberation of molecules cleaved from the gel support can be measured directly by flow photometry (UV, IR, conductivity, etc.) and recorded continuously. On opening an outlet valve on the bottom, the reactor is emptied rapidly and completely by spinning off. 

Fig. 61. The photometric synthesis control system in cooperation with the centrifugal reactor to monitor the Merrifleld process...

The utilization of the photometric synthesis control [95] was already mentioned in Sect. 3.1.3, 3.2.4, and 3.3.6 (Fig. 61). The system consists of a two-channel flow photometer with reference cell technique operating on two wavelengths. It is connected to a continuous line recorder with fifteen times automatic scale expansion at constant sensitivity and a graphic integration supplement. The photometer reference flow cell of a wide inner diameter has an optical path of 5 mm. It is inserted between the metering system of the synthesizer and the centrifugal reactor and allows a flow rate of 5 to 10 liters/hour. 

In contrast the sample flow cell, which is connected to the centrifugal reactor for perfusion with reaction liquids, has a narrow inner diameter and an optical path of 1 mm. This difference to the reference cell was additionally introduced to manage in part the wide range of varying concentrations to be measured in the flow-through system by optical subtraction of solvent influences with the reference technique. 

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