Specific Methods of Synthesis

In the preparation of l,l-diphenyl-X -phosphorin, Markl used the following sequence  

118 could be obtained only as a yellow powder (Xmax = 409 nm, in CH3OH), oxidizing in the presence of air to compounds which range in color from red to violet the oxidation products were not identified. Acids cause reconversion to the phosphonium salt 119. The perchlorate (7i9(X = CIO4)) crystallizes from acetonitrile with one mole of solvent (m. p. 175-6 °C) and has IR-absorption bands at 1626, 1572 and 1550 cm . The parent compounds of this series, 1,1-dihydro-X -phosphorin or l,l-dimethyl-X -phosphorin 118, H or CH3 in place of CgHs, respectively) are not known. 

l-diphenyl-X -phosphorins 720a-c are colored, easily autoxidizable, noncrystalline compounds which were prepared by multistep synthesis, the last step being conversion of the corresponding 1.1-diphenyl-2.3-benzophosphonium perchlorates 727 a—c by aqueous alkali. 

These X -phosphorins 720 a-c also fail to react with carbonyl compounds. However, they are attacked by electrophiles (H or alkyl cations) at the C—2 position. In this manner new 1,1-diphenyl-2,3-benzo-X-phosphorins which are sustituted at positions C—2 (and C-4) can be prepared. Diazonium ions attack at C—4 to form azocompounds if an excess is used, C—2 is also substituted Hydrolysis with hot water affords 747. The reaction with ortho-formic acid ester forms a cyanine dye having a bridge at the C—4 positions 142 The experimen- 

Lieb and Merz have described the carbanionic addition of lithium or magnesium organometallic compounds to the P atom of 2.4.6-triphenyl-X -phos-phorins, which form deep red s ts 143. These can be alkylated either at the P atom to form X -phosphorins 144 or at C—2 to yield 1,2-dihydro-X -phosphorins 145. Acylation with benzoylchloride affords the 1,4-dihydro-X -phosphorin derivatives 146. Addition of acids or water leads to the synthetically important intermediates 147 which can be reconverted to the X -phosphorin-salts 143 by 2 N NaOH. 

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The aim of the present book is to offer a comprehensive, up-to-date survey of the numerous facets of the subject. As it falls in the Applied Physics series, the book focuses especially on basic chemical and physical concepts. We have, as much as possible, stressed clarity over completeness, even avoiding some obscuring aspects that, although important, might be too specialized and discourage the reader. In that case, of course, the references help the reader who needs more detailed information to find it easily. On the other hand, all the experimental aspects, original techniques, and specific methods of synthesis, measurement, control, and analysis have been developed thoroughly. 

All the addition polymers we have considered so far (Table 1.1) contain only one type of repeating unit or mer in the chain. Polymers can also be synthesized by the aforesaid processes with more than one type of mer in the chain. Such polymers are called copolymers. They are produced by polymerizing a mixture of monomers (copolymerization) [12] or by special methods. Copolymers can be of different types, depending on the monomers used and the specific method of synthesis. The copolymer with a relatively random distribution of the different mers in its structure is referred to as a random copolymer. Representing, say, two different mers by A and B, a random copolymer can be depicted as... 

In the first chapter, devoted to thiazole itself, specific emphasis has been given to the structure and mechanistic aspects of the reactivity of the molecule most of the theoretical methods and physical techniques available to date have been applied in the study of thiazole and its derivatives, and the results are discussed in detail The chapter devoted to methods of synthesis is especially detailed and traces the way for the preparation of any monocyclic thiazole derivative. Three chapters concern the non-tautomeric functional derivatives, and two are devoted to amino-, hydroxy- and mercaptothiazoles these chapters constitute the core of the book. All discussion of chemical properties is complemented by tables in which all the known derivatives are inventoried and characterized by their usual physical properties. This information should be of particular value to organic chemists in identifying natural or Synthetic thiazoles. Two brief chapters concern mesoionic thiazoles and selenazoles. Finally, an important chapter is devoted to cyanine dyes derived from thiazolium salts, completing some classical reviews on the subject and discussing recent developments in the studies of the reaction mechanisms involved in their synthesis. 

For the statistical copolymer the distribution may follow different statistical laws, for example, Bemoullian (zero-order Markov), first- or second-order Markov, depending on the specific reactants and the method of synthesis. This is discussed further in Secs. 6-2 and 6-5. Many statistical copolymers are produced via Bemoullian processes wherein the various groups are randomly distributed along the copolymer chain such copolymers are random copolymers. The terminology used in this book is that recommended by IUPAC [Ring et al., 1985]. However, most literature references use the term random copolymer independent of the type of statistical distribution (which seldom is known). 

The specific surface area of a solid is the surface area of a unit mass of material, usually expressed as m g . There is an inverse relationship between surface area and particle size. Massive crystals of hematite from an ore deposit (e. g. specularite) may have a surface area 1 m g". As particle size/crystallinity is governed largely by the chemical environment experienced during crystal growth, the surface area of a synthetic iron oxide depends upon the method of synthesis and that of a natural one, upon the environment in which the oxide formed. 

In summary, it is predictable that collections of synthetic chemicals and of NPs will not be identical because their methods of synthesis are fundamentally different. However, the differences might be of little predictive value when seeking chemicals with specific properties or functions. 

Volume II describes 17 additional functional groups and presents a critical review of their available methods of synthesis with preparative examples of each. Attention is especially paid to presenting specific laboratory directions for the many name reactions used in describing the synthesis of these functional groups. 

The acid has been formed by the reduction of 2-carboxyphenylacetaldehyde, itself available from indene by ozonolysis (57JA3165). This is one of the most convenient methods of synthesis of isochroman-l-one, which is obtained in a 70% overall yield from indene (Scheme 236), and has been used in the synthesis of isochromanones with specific deuterium labels <8ljcs(Pl)l685). 

The importance of these three classes of unsaturated compounds is that they contain many naturally occurring examples having specific biological activity. For this reason their general methods of synthesis are of interest. Furthermore, their particular functional features are to be found embedded in the structures of more complex acyclic, alicyclic and polycyclic molecules. Thus the incorporation of the simpler structures as building blocks in multistage syntheses of, for example, antibiotics has been one of the synthetic challenges of recent decades. 

Specific properties of polysilanes have been linked to the method of synthesis.35 For example, in the case of anionic polymerization of poly[l-(6-methoxy-hexyl)-l,2,3-trimethyldisilanylene] a new type of chromism was induced in the polysilane film by the difference in the surface properties of substrates and was termed a surface-mediated chromism. The polysilane exhibited thermochromism with an absorption maximum at 306 nm at 23°C, but <15°C a band at 328 nm began to appear. A monolayer of the polysilane was transferred onto both a clean hydrophilic quartz plate and a hydrophobic one treated with hexamethyldisilazane by the vertical dipping method. With the hydrophobic plate, a broad UV absorption at 306 nm is obtained, whereas the absorption on a hydrophilic plate shifts to 322 nm. The conformation of the polysilane is preserved by hydrogen bonding between the silica surface and the ether section of the substituent on the hydrophilic plate. The polysilane is attached to the hydrophobic surface only by van der Waals forces, and this weaker interaction would not sustain the thermodynamically unstable conformational state that is attained on the water surface. 

Specific procedures for the synthesis of M0CI4, MoCl, and M0CI2 are described in the sections that follow. Other methods of synthesis are also summarized in these sections. Procedures for the synthesis of M0CI5 have been given in Inorganic Syntheses 7, 167 (1963) and 9, 135 (1967). The industrial method is the direct chlorination of metal and is recommended in some laboratories.12-18 A convenient laboratory technique is the liquid-phase reaction system that uses refluxing thionyl chloride and molybdenum (VI) oxide.14... 

This chapter reviews the body of literature (to August 2000) that deals specifically with kinetic studies of the reactions of silenes and disilenes and the mechanistic information that has been derived from them. The spectroscopic properties, structures, methods of synthesis and qualitative aspects of the reactivity of silenes and disilenes have been covered comprehensively in the preceding two volumes in this series and elsewhere, and so will not be treated extensively here. 

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