Sealed tube reaction

Various inorganic, organic, and organometaUic compounds are known to cataly2e this polymerization (4,8,9). Among these, BCl is a very effective catalyst, although proprietary catalysts that signiftcandy lower polymerization temperature from the usual, sealed-tube reaction at 250°C are involved in the industrial manufacture of the polymer. A polycondensation process has also been developed for the synthesis of (4) (10—12). This involves elimination of phosphoryl chloride from a monomer prepared from (NH 2 04 and PCl. ... 

Electronegative groups do not invariably prevent nuclear bromination, but reaction conditions must be much more severe, and the orientation of substitution may be affected by the substituent. Thus 6-nitroquinoline was brominated in sulfuric acid at 100°C to give the 8-bromo product (71) in 51% yield 8-methyl-5-nitroquinoline gave a 69% yield of the 7-bromo derivative (72) under similar conditions, whereas 7-chloroquinoline was transformed into the 5-bromo product (93%) (88CHE892) (Scheme 35). In a sealed tube reaction with bromine, 8-nitroquinoline gave a mixture... 

The reaction between anihnes and malonic esters generates two equiv of ethanol, which could affect the equilibriiun between the starting material and the product (Fig. 5). Therefore, in a sealed tube reaction, it is necessary to keep the volume and reactant concentrations low in order to shift the equi-hbrium towards product formation. Thus, large-scale experiments are not practical using this procedure (Fig. 5). 

The compound [Cl2SiFe(CO)4]2 is obtained from Fe(CO)j and HSiClj, in a sealed tube reaction (148). It is presumably a member of the family of Group IVB-iron metallocycles of structural type (XI) (40, 246). Two Ni... 

Tubes for sealed tube reactions, such as the Carius determination of halogens and sulphur, can be made from Pyrex, Monax or soda glass. The mechanical strength of the glasses is about the same, but a soda Carius tube is much more likely to crack as a result of thermal strain than a Pyrex or Monax one. The Carius tubes are usually made from tubing of approximately 20-25 mm diameter and 3 mm wall thickness—Pyrex extra heavy tubing of external diameter 22 mm has a wall thickness of 2-5-4 mm and can be used up to 600°C. 

In order to better understand the reaction of CIRh(PPh3)3 and PMMA model compound studies were begun. The model of choice is dimethylglutarate, DMG, since this provides a similar structure and a suitable boiling point for sealed tube reactions. 

An improved method of preparing alkyl azides has been reported wherein Carbitols are used as solvents for the interaction of an alkyl halide and commercial sodium azide [10]. The use of activated sodium azide [34] is not necessary. Sealed-tube reactions for alkyl azides are hazardous a violent explosion has been reported in an attempt to seal such a tube [35]. No reactions reported in this chapter involve sealed tubes. Table II describes the conditions and azides prepared using the Carbitol solvents. 

Caution. The synthesis of N,N-bis(2-mercaptoethyl)2-methylthioethylarmne involves a sealed-tube reaction that should be conducted behind an explosion shield. 

Fig. 5.1. Simple vacuum line. A iineof this sort might be used to transfer volatile samples to infrared gas cells, NMR tubes, etc. It might also be used for loading tubes for sealed-tube reactions and for vacuum sublimations.

Sealed tube reaction vessels, 42-43, 202-206 Sealing evacuated tubing, 257-258 Seals glass ... 

B. Sealed Tube Preparations. Sealed tube reactions and purifications afford good exclusion of the atmosphere and permit operations at moderate pressures. The latter capability makes it possible to work with highly volatile solvents, such as liquid ammonia, at room temperature. Since the sealed tube is often loaded on a high-vacuum line, the details on these techniques are given in Chapter 9. 

The sealed tube reaction of Bi203 with BiF3 at 670°C produces BiOF together with three phases having the composition BiIF3 2x Single crystals of BiOF have been studied by infrared spectroscopy (113). 

These reactions appear to involve a rapid stripping process, reminiscent of that occurring in a mass spectrometer (Section IV,D). Hydrogen and CO are lost before the system is able to reach equilibrium the products are therefore different from those formed in sealed-tube reactions and favored thermodynamically. Provided that it is possible to synthesize sufficiently volatile precursors with the desired metal sili-... 

Molybdenum oxide trichloride has been prepared by heating molybdenum(VI) oxide or molybdenum dioxide dichloride with molybdenum(V) chloride. Molybdenum(VI) oxide tetrachloride is a by-product of the latter reaction.1 It was also prepared by the sealed-tube reaction of liquid sulfur dioxide with molybdenum (Y) chloride2 and by the thermal decomposition of molybdenum oxide tetrachloride in a stream of nitrogen. In the following procedure, it is prepared by reducing molybdenum oxide tetrachloride with refluxing chlorobenzene.4... 

Apart from bis(benzene)chromium and other bis(arene) metal compounds, a huge number of mono(arene) transition metal complexes were also prepared in the golden 1950s . In 1957, Fischer and Ofele reported the synthesis of (C6H6)Cr(CO)3, the first representative of the family of arene metal carbonyls [64], The original preparative procedure (a sealed-tube reaction of Cr(CO)6 and Cr(C6H6)2 at 220°C) was soon replaced by a more convenient synthesis, based... 

The hexaamine complex can only be prepared in sealed tube reactions (equation 34), unless the incorporation of the sixth ammine ligand is catalyzed by ethanol. In contrast, the pentaammine complexes are very accessible, and their anation and aquation reactions (Scheme 11) have been exhaustively... 

Yet another major advance in arene-metal chemistry was made in 1957 by Fischer and Ofele 95) y who found that a sealed tube reaction involving chromium hexacarbonyl, bis(benzene)chromium, and benzene produced the half-sandwich compound benzene-chromium tricarbonyl (XXVII). 

There is a variety of reported routes to the halotrimethylgermanes. These procedures have caused considerable difficulty in that they are often irreproducible, require long reaction times, involve sealed-tube reactions that are difficult to perform on a large scale, or produce only fair yields of products. The following procedure, a modification of one used by Mironov and Kravchenko, circumvents these problems. 

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