Preparation and Formation

From Lead Compounds and Grignard Compounds. The most common laboratory method for synthesis of tetraethyllead is the reaction of a lead(ll) halide, usually PbCl2, with a Grignard reagent in dry ether according to the general equation  

Half of the lead in the starting reagent separates as finely divided elemental lead. 

Upon reaction of C2H5MgCl and Pb(OOCCH3)2 in THF in the presence of C2H5CI, first for 15 min at 5 °C, then for 30 min at ambient temperature, a yield of 87% Pb(C2Hs)4 is obtained [543]. 

For the ethylation of elemental lead with Grignard compounds in the presence of ethyl halide, see the subsection From Lead and Ethyl Halides or Ethyl Esters . 

From preliminary experiments it was speculated that the isotopes of lead might be separated, owing to different behavior during the reaction of PbCl2 with CaHgMgl [20], however, this was disproved in subsequent work [45, 46]. 

Many formation reactions and the principal methods for the preparation of PH3 both on laboratory and industrial scales are known for a long time and are already described or mentioned in Phosphor C, 1965, pp. 7/16. 

Samarium monoselenide can be prepared from Sm2Se3 at 1700°C in a vacuum, Guittard, Benacerraf [12]. Thermal decomposition of the sesquiselenides M2Se3, M = La to Nd and Gd, or the diselenides at 1800°C and 10 Torr results in a mixture of MSe and M3Se4 [12], Obolonchik, Mikhlina [13]. Small amounts of MSe, M = La and Ce, in a mixture with other selenides are obtained from M2Se3 and a calculated amount of metal M at 1700°C in 1 h [12]. The dull black YbSe sample prepared from Yb2Se3 in an H2 stream at 1250°C for 8 h contained some oxide, Senff, Klemm [14]. 

Although no D-glucosone was obtained by the action of formaldehyde on D-glucose phenylosazone,19 Briill28 successfully decomposed the osazone with an excess of pyruvic acid. An improved procedure has been described, and the decomposition of D-glucose phenylosazone with glyoxal has been reported.18 

Partially methylated derivatives of D-glucosone have been prepared by decomposition of the corresponding partially methylated phenylosazones with p-nitrobenzaldehyde osones have been obtained from 5-0-methyl-D-glucose phenylosazone and from 3,4,5-tri-O-methyl-D-glucose phenylosazone in this way.22 Although 6-0-methyl-D-glucose phenylosazone is not altered by heating with benzaldehyde or piperonal in aqueous ethanolic 

It has recently been reported21 that a mixed osazone of 3,4-di-O-methyl-D-glucose can be converted, by treatment with p-nitrobenzaldehyde, into an osone which reacts with phenylhydrazine to give 3,4-di-O-methyl-D-glucose phenylosazone. Von Lebedev29 claimed to have obtained D-glu-cosone 6-phosphate, isolated as an amorphous lead salt, by the action of hydrochloric acid on the phenylosazone prepared from D-fructose 6-phosphate. 

From Grignard Compounds. Pb(CH3)4 is readily prepared by the reaction of PbClg with Grignard reagents In ether according to the general equation 

dry PbCl2 (1.8 mol) is added slowly to a solution of excess CH3MgCl (4 mol) in absolute diethyl ether under constant shaking. The reaction mixture is refluxed for 2 [6] to 5 h [5] on a water bath, cooled in ice and decomposed with water, but not acidified. After extracting 

No isotopic effect was observed in the reaction of CHgMgl and Pbl2 [25, 27]. Pb(CH3)4, prepared from CHgMgl, may contain traces of iodine these are removed by treating with freshly prepared AggO for several days [10, 43] purification by distillation is described in [5, 10, 44]. For a discussion of the mechanism of the reaction of Grignard reagents and lead(ll) compounds, see [19] and the appropriate literature in Section 1.1.1.2. 

For the reaction with methyl cobalamin (methyl vitamin B12), see From Lead(ll) and Lead(IV) Compounds and CH3I or Other Methylating Agents , p. 71. 

From Alloys and Methyl Halides. One of the commercial procedures now in use for the manufacture of Pb(CH3)4 is based on the reaction of lead-sodium alloy with methyl halide. Actually, the first paper on Pb(CH3)4 already mentioned the preparation from CH3I and a lead-sodium (5 1) alloy [62, 63]. 

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Formation and Preparation.—1. From its Elements.—(a) Above 200° C. hydrogen and sulphur interact with appreciable velocity, forming hydrogen sulphide.3 Relow 350° C. the combination proceeds slowly until one or other of the reagents is entirely consumed, but above this temperature, although the reaction is naturally more rapid, the final product is an equilibrium mixture, the change being representable thus ... 

Formation and Preparation.—Chlorine and sulphur dioxide will only unite under some accelerating influence. It was by the interaction of these gases in sunlight that sulphuryl chloride was first obtained by Regnault in 183S. 

Formation and Preparation.—(1) Sulphur trioxide is formed to a small extent together with sulphur dioxide when sulphur 1 or compounds of sulphur 2 are burned in oxygen or air (see p. 103). In an oxygen bomb, in the presence of a compound which on combustion yields water vapour and oxides of nitrogen, for example ammonium nitrate, the combustion goes completely to sulphur trioxide (see p. 45 ).3... 

Formation and Preparation.—(1) Hydrogen and selenium combine on heating H.+Se H.Se. 

Formation and Preparation.—(1) Powerful oxidising agents are able to convert tellurium into the sexavalent condition, the product obtained in the presence of water being telluric acid, whereas in the presence of an alkali a tellurate is obtained. 

The formation and preparation of phosphine.—The modes of preparation are sometimes divided into (i) those which furnish the spontaneously inflammable gas, i.e. the gas inflames when it comes in contact with air at ordinary temp, and press, and (ii) those which furnish the non-spontaneously inflammable gas which takes fire only at an elevated temp, or under a reduced press. Since these divergent qualities are determined by the presence or absence of traces of hydrogen hemi-phosphide, (PH2)2, and since this impurity may or may not be removed from the gas by suitable treatment, there are no essential differences in the modes of preparation of the spontaneously accendible and non-accendible forms of the gas. T. Graham 4 made a special study of the conversion of the spontaneously inflammable gas into the non-accendible form. He said ... 

Figure 35. Silver-mediated C X bond formation and preparation of diiodobenzene derivative.

The discussion of this somewhat heterogeneous collection of free and substituted dicarbonyl carbohydrates will be divided into (a) dialdehyde compounds, (b) keto-aldehyde compoimds having free or substituted carbonyl groups, and (c) the diketo compounds. Each Section (except the last one, containing only a few members) will be divided into (a) an introduction consisting of a general discussion concerning formation and preparation, (b) a description of individual compounds, and (c) a discussion of properties and reactions. A short discussion on oxidized polysaccharides is included before the Tables of dicarbonyl carbohydrates and their derivatives. 

The methods of its formation and preparation are given under leucine. 

Professors Nissim Garti and Axel Benichou review formation and preparation of intricate multiple emulsions, of both the water-in-oil-in-water and oil-in-water-in-oil types. Emulsions of this type occur especially when mixtures of both hydrophobic and hydrophilic stabilizers are used. These mixtures can be either commercial or naturally occurring. This chapter is an important complement to the traditional view of simple emulsions with only one dispersed phase. 

In a consultation between them, it was decided to keep the previous format, and prepare an updated compilation D G Howery volunteered to help, and provided a great deal of material for the compilation. An early draft has been circulated among the members of Commission V 6, and has been approved in principle This draft has now been completed with further data, and brought up to date to the end of 1971 ... 

Comparative Data for M2Se3 29.1.2.3.1 Formation and Preparation General... 

Formation and Preparation Preparation of Bulk Polycrystalline Samples... 

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