Phthalides phthaleins

Indicator dyes for pH having the phthalide structure fall into two types, the phthaleins, shown in the lactone form of general structure (1.66) and the sulfoph-thaleins (1.67). The synthetic pathways to these products are very similar. The phthaleins (1.66) are made by reacting phenol with phthalic anhydride in the presence of Lewis acid catalyst, e.g. ZnCl, whilst (1.67) are obtained by using 2-sul-fobenzoic anhydride (Figure 1.20). 

Thus the phthaleins are triphenylmethane derivatives, being all derived from phthalophenone (diphenyl phthalide). 

Phenolphthalein (213) and its derivatives have found application in the polymer area. Phenol-phthalein itself (213) and substituted derivatives were polymerized with 2,6-dichlorobenzonitrile to form heat-resistant polycyanoaryl ethers <89JAP(K)01225631). A tetrabromo derivative (256) was polymerized with epichlorohydrin to form flame-retardant epoxy resins. The phthalide-derived... 

Other Names l,r-Naphthol-4,4 -phthalein Phthalide, 3,3- w(4-hydroxy-l-naphthyl)- a-Naphtholphthalein 1-Naphtholphthalein 3,3- w(4-hydroxy-l-naphthyl)-l,3-dihydroisobenzofuran-l-one 3,3--Bw(4-hydroxy-l-naphthyl)phthalide Di-p-a-Naphtholphthalide Naphtholphthalein blue p-a-Naphtholphthalein... 

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