Hair Primary Intermediates

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. ... 

Oxidation Hair Colorant. Color-forming reactions are accomplished by primary intermediates, secondary intermediates, and oxidants. Primary intermediates include the so-called para dyes, -phenylenediamine, -to1nenediamine, -aminodiphenylamine, and -aminophenol, 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 -diamines, w-aminophenols, polyhydroxyphenols, and naphthols. Some of the more important oxidation dye colors are given in Figure 1. An extensive listing is available (24,28). 

The use of primary intermediates as sole dye precursors severely limits the range of shades some couplers are therefore sometimes added. They do not themselves develop a significant color effect as such but if present in primary intermediates they modify the resulting colors. The usual couplers are 1,3-diami-nobenzene (blue), 3-aminophenols (red), and resorcinol (yellow-green). This technique is mostly used for human hair (see Section 5.4.2), the oxidation steps being performed at around pH 9.5 with hydrogen peroxide. 

This size enlargement is largely responsible for fixing the dye in the hair. With the proper choice of substituents, any color from yellow to blue can be obtained [9, pp. 279-283], [26] and Scheme 5.2. If one or two primary intermediates are mixed with various (usually three to five) couplers, a range of colors is produced in the hair, giving the desired shade as an overall impression. 

The principal red couplers are 3-aminophenol [591-27-5], 5-amino-2-methyl-phenol [2835-95-2], and 1-naphthol [90-15-3]. Yellow-green couplers include resorcinol [108-46-3], 4-chlororesorcinol 195-88-5, benzodioxoles, and 2-methyl-resorcinol [608-25-3] and its derivatives. The importance of the yellow-green couplers lies in the broad-band absorption of the dyes produced, which makes natural-looking hair shades possible. Table 5.4 lists a range of colors obtained by reaction of primary intermediates with different couplers. 

Table 5.4 Combinations of primary intermediates and couplers used in hair colorants...

When used alone, the primary intermediates give a quite limited shade range following oxidation on hair. To enhance the range of available hair colors, the primary intermediates are oxidized in the presence of suitable couplers ) Whereas most couplers do not... 

Permanent hair dyes are often derivatives of an aromatic amine, discovered as a hair dye in 1883, called /Mra-phenylenediamine (H2N-C6H4-NH2), including primary intermediates such as pcirci-aminophenol, dihydroxybenzene, 4-methylaminophenol, tetraaminopyrimidine, 2-aminomethyl-4-aminophenol, and / ara-aminodiphenylamine. The / zrra-phenylenedi-amine compound produces a black color, with its derivative parci- mmo-diphenylaminesulfonic acid used in blond formulations. Couplers are generally aromatic phenols or amines that have an available site that is subject to electrophilic interaction. Typical couplers include chemicals such as resorcinol, wrte-phenylenediamine, 2,4-diaminoanisole, mrm-aminophenol,... 

Hair dyes. Primary intermediates and couplers used in semi-permanent and permanent hair-colouring procedures. Allergies were described to ... 

Synonyms 2-methyl-i,4-benzenediamine sulfate (1 1) 2,5-diaminotoluene sulfate (1 1) p-toluenediamine sulfate (1 1) toluene-2,5-diamine sulfate(i i) 2,5-diaminotoluene sulfate 2,5-toluenediamine sulfate (1 1) toluene-2,5-diamine sulfate C.I. 76042 Uses primary intermediate in various permanent hair dyes. TOLUENE-2,5-DIAMINE SULFATE A... 

The formulation of almost all permanent hair-dye products uses the so-called oxidative hair dyes. These chemicals are often referred as intermediates, because most of them are uncoloured and produce coloured compounds through a process of oxidative condensation when mixed with oxidizing products just before use. In fact the hair colour is formed when a dye precursor (usually referred to as base or primary intermediate) is oxidized by the oxidizing agent (also known as the developer) to produce an imine, which reacts rapidly with the so-called modifier (also known as coupler). 

Some chemicals used as bases (or primary intermediates) in hair-dye oxidative products (adapted... 

C -Keratin, which is the primary component of wool and hair, consists of two right-handed o helices intertwined to form a type of left-handed superhelix called an a coiled coil, ot-Keratin is a member of a superfamily of proteins referred to as coiled-coil proteins (Figure 2,43). In these proteins, two or more a helices can entwine to form a verv stable structure, which can have a length of 1000 A (100 nm, or 0.1 jiim) or more. There are approximately 60 members of this family in humans, including intermediate filaments, proteins that contribute to the cell cytoskeleton (internal scaffolding in a cell), and the muscle proteins myosin and tropomyosin (Section 34.2). Members of this family are characterized by a central region of 300 amino acids that contains imperfect repeats ol a sequence of seven amino acids called a heptad repeal. 

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