Primary intermediates

Primary intermediates Primary nucleation Primary ozomdes Primary plasticizer Primary recycling Primary structure Primary tastes Primatene Mist Primaxin Prime+... 

Oxidation H ir Colorant. Color-forming reactions are accompHshed by primary intermediates, secondary intermediates, and oxidants. Primary intermediates include the so-called para dyes, -phenylenediamine, -toluenediamine, -aminodiphenylamine, and p- am in oph en o1, which form a quinone monoimine or diimine upon oxidation. The secondary intermediates, also known as couplers or modifiers, couple with the quinone imines to produce dyes. Secondary intermediates include y -diamines, y -aminophenols, polyhydroxyphenols, and naphthols. Some of the more important oxidation dye colors are given in Figure 1. An extensive listing is available (24,28). 

Fig. 1. Quinine knines from primary intermediates couple with secondary intermediates to form viscous colors.

Attempts to broaden the range of materials available as dye precursors have been made (34,35). Oxidative dyes based on pyridine derivatives produce less sensitization than those based on benzene derivatives (36) however, they lack tinctorial power, lightfastness, and availabihty. Derivatives of tetra am in opyrim i din e are claimed to act as primary intermediates to give intense shades with good fastness and excellent toxicological properties (37). 

Efficiency of Intermediate Formation. The variation of the efficiency of a primary intermediate with conversion of the feed hydrocarbon can be calculated (22). Ratios of the propagation rate constants ( 2 / i) reactor type (batch or plug-flow vs back-mixed) are important parameters. 

Eig. 2. Efficiency to a primary intermediate as % of maximum (zero conversion) efficiency x axis is feed conversion. Parameters are oxidation rate-constant ratios ( 2 / i) for primary intermediate vs feed and reactor type A, plug-flow or batch B, back-mixed. 

The maximum yield of a primary intermediate, as well as the efficiency (and conversion) at maximum yield, can also be calculated (22). Maximum yield plots are shown in Eigure 3. 

Intermediates Glassification. Intermediates may be conveniently divided into primary intermediates (primaries) and dye intermediates. 

Primary Intermediates. Primary intermediates are characteri2ed by one or more of the following descriptions, which associate them with raw materials rather than with intermediates. 

A primary intermediate has estabUshed usage in basic industries such as mbber, polymers, or agrochemicals in addition to dyes. 

Primary intermediates were originally manufactured within the dyes industry. All the significant primaries, about 30 different products, are derived from ben2ene, toluene, or naphthalene. Actual production figures for primaries are not readily available, and in any event the amounts used within the dyes industry are variable. The primaries are Hsted here with a reference to the Eniyclopedia article that covers them in detail including production and consumption figures. 

Process Primaries Intermediates (common usage) Colorants (common usage)... 

Small and Browning agree with Schbpf and Winterhalder that thebainone methyl enolate (formed by 1 6 addition in which the oxygen bridge is ruptured and ethylenic linkages produced at C —C and C —C ) may be the primary intermediate in tWs reaction since it is hydrogenated... 

A reaction mechanism in which the ( )-diazoate is formed by attack of the diazonium ion by a hydroxide ion in such a way that the ( )-diazoate is the primary intermediate (i. e., reaction sequence 6 - 3 in Scheme 5-14) is not consistent with the observation that the isomerization rate constant is independent of the hydroxide ion concentration. 

Platinum is the only acceptable electrocatalyst for most of the primary intermediate steps in the electrooxidation of methanol. It allows the dissociation of the methanol molecule hy breaking the C-H bonds during the adsorption steps. However, as seen earlier, this dissociation leads spontaneously to the formation of CO, which is due to its strong adsorption on Pt this species is a catalyst poison for the subsequent steps in the overall reaction of electrooxidation of CHjOH. The adsorption properties of the platinum surface must be modified to improve the kinetics of the overall reaction and hence to remove the poisoning species. Two different consequences can be envisaged from this modification prevention of the formation of the strongly adsorbed species, or increasing the kinetics of its oxidation. Such a modification will have an effect on the kinetics of steps (23) and (24) instead of step (21) in the first case and of step (26) in the second case. 

Organic hydroperoxides, such as -butyl hydroperoxide, (0113)30—0-OH, likewise induce polymerization in vinyl monomers through the action of free radicals formed as primary intermediates in their decomposition. The following compounds, or classes of compounds, also are effective polymerization initiators at temperatures where they undergo slow thermal decomposition by mechanisms which are believed to involve the release of free radicals as indicated ... 

Oxidation chemistry of a-tocopherol (1) generally involves three primary intermediates (2-4), which are formed according to the respective reaction conditions used, their... 

The third primary intermediate in the oxidation chemistry of a-tocopherol, and the central species in this chapter, is the orr/zo-quinone methide 3. In contrast to the other two primary intermediates 2 and 4, it can be formed by quite different ways (Fig. 6.4), which already might be taken as an indication of the importance of this intermediate in vitamin E chemistry. o-QM 3 is formed, as mentioned above, from chromanoxylium cation 4 by proton loss at C-5a, or by a further single-electron oxidation step from radical 2 with concomitant proton loss from C-5a. Its most prominent and most frequently employed formation way is the direct generation from a-tocopherol by two-electron oxidation in inert media. Although in aqueous or protic media, initial... 

Reaction of phthalazinedione 83a with tropone provided adduct 126, which was photochemically transformed into acid 128a in acetonitrile-water solution at room temperature, or to its methyl ester 128b when the reaction was performed in methanol (Scheme 30). Ketene 127 was implicated as the primary intermediate on irradiation and the final products of addition of water and/or methanol 128a and 128b, respectively, were isolated in high yields [72JCS(P1)783]. 

A molecule of linear alkyl ether possesses a very convenient geometry for intramolecular hydrogen atom abstraction by the peroxyl radical. Therefore, chain propagation is performed by two ways in oxidized ethers intermolecular and intramolecular. As a result, two peroxides as primary intermediates are formed from ether due to oxidation, namely, hydroperoxide and dihydroperoxide [62],... 

Primary intermediates, 9 265-266 Primary intrinsic magnetic properties, of M-type ferrites, 11 67-68 Primary ions, backscattered, 24 106 Primary irritancy toxicology studies, 25 218... 

There are two mains aspects of the role of dimerization of intermediates on the electrochemical responses that are worth investigating in some detail. One concerns the effect of dimerization on the primary intermediate on the current-potential curves that corresponds to the first electron transfer step, the one along which the first intermediate is generated. Analysis of this effect allows the determination of the dimerization mechanism (radical-radical vs. radical-substrate). It is the object of the remainder of this section. 

Determination of the Standard Potential for the Formation of Very Unstable Primary Intermediates... 

FIGURE 2.29. Determination of the standard potential for the formation of a very unstable primary intermediate. 

There has been a series of papers on the deoxygenation of 2-nitrophenyl phenyl ethers and sulphides. Of particular interest has been the role of pentacovalent intermediates (47) in these reactions. These are certainly not the primary intermediates in the reactions but are of great importance in determining the course of the reaction. Their genesis is thought to be that shown in Scheme 3.57... 

The anodic oxidation of amides and carbamates is one of the most general and efficient electrochemical reactions known [115]. The primary intermediate... 

The corresponding reaction of cyclohexylbignanide has given comparable results [607). The primary intermediate was not identified but, as a basis for discussion, was formulated as the six-membered bridged carbonyl compound (CXXII). 

The overall picture certainly became no simpler when quite a few examples were encountered where the nature of the nucleophile is decisive for the position at which the photosubstitution occurs. Just one recent example, taken from the work of Lammers (1974) is given in equation (8). To account for this influence of the nucleophile, the formation of an excited complex between aromatic compound and nucleophile has been suggested as the primary intermediate (de Vries, 1970). 

Acetylene first became the primary intermediate molecule in chemical synthesis in the early twentieth century. As noted previously, the triple bond in acetylene is ideal to add one or two small molecules. For example, addition of one mole of water produces vinyl alcohol,... 

CgQ readily reacts with organoHfhium and Grignard compounds with alkyl, phenyl or alkynyl groups to form the anions RCgg as primary intermediates [2-10], This... 

The main dye prodncing system nsed in hair coloration involves the oxidation of a primary intermediate in the presence of a colonr coupler to produce the coloured molecule. The primary intermediates are 1,4-phenylenediamines or 1,4-aminophe-nols and the colonr conplers are 1,3-phenylenediamines or 1,3-aminophenols. The primary intermediates are oxidised by peroxides to give the colonred benzo-quinonediimines or monoimines, which react with the couplers to give indoamines or indophenols, e.g. (2.52) and (2.53), depending on the natnre and ratio of the reactants, as shown schematically in Fignre 2.20. ... 

Certain amines are no longer nsed becanse of toxicity concerns, but there is stiU a wide range of colours available from the system. A few of the colours obtainable are illnstrated in Table 2.8. They range from brown to blue depending on the primary intermediate and the colour coupler. 

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