Rosolic acid

The leuco base of para-rosolic acid is the tri-hydroxy tri-phenyl methane 

The dye compound which, strictly speaking, is not a salt but a quinone is obtained directly by oxidizing the leuco base, the intermediate carbinol losing water without the action of an acid. Dyes of this group are not very numerous, rosolic acid itself being used chiefly as an indicator. It is interesting that the compound was prepared long before Perkin, Hofmann and Fisher made the first actual synthetic dye and established 

An important group of dyes known as the phthaleins and t ified by the common indicator phenolphthalein are derivatives of tri-phenyl methane, but because they do not possess the same structure as the three preceding groups are placed in a separate series known as the pyronines. 

Preparation from Phthalic Acid.—In discussing phthalic acid (p. 691) we spoke of the fact that phthalic anhydride or phthalyl chloride with phenol yields phenolphthalein. The reaction takes place in the presence of anhydrous zinc chloride as a dehydrating agent or in the presence of aluminium chloride (Friedel-Craft). Phthalyl chloride being the unsymmetrical compound (p. 692), the two reactions are represented as follows  

Tri-phenyl Methane Derivative.—That this compound is a derivative of tri-phenyl methane is proven by the following series of relationships. When phthalyl chloride is reduced with hydrogen we obtain phthalide (p. 693). 

Other Names 2,5-Cyclohexadien-l-one, 4-[ w(p-hydroxyphenyl)methylene]- Aurin 4,4 -Dihy-droxyfuchsone 4-(p,p -Dihydroxybenzhydrylidene)-2,5-cyclohexadien-1 -one d-CBwCp-hydroxy-phenyl)methylene]-2,5-cyclohexadien-l-one Aurin 555 Aurine C.I. 43800 Corallin CoraUin Spirit Soluble NSC 7805 Pararosolic acid RosaUc acid Spirit Aurine p-Rosolic acid CA Index Name 2,5-Cyclohexadien-l-one, 4-[fcis(4-hydroxyphenyl)methylene]-CAS R istry Number 603-45-2 Merck Index Number 881 Chemical Structure 

Chemical/Dye Class Triphenylmethane Molecular Formula C19H14O3 Molecular Weight 290.31 pH Range 6.6-8.0 

Solubility Practically insoluble in water, benzene lieely soluble in ethanol UV-Visible ( lmax) 534.6 mn, 479.5 mn, 482 nm Melting Point 309°C (decompose) 

Boiling Point (Calcd.) 543.0 + 50.0°C Pressure 760 Torr Synthesis Synthetic methodsi  

Major Applications Antireflective coatings,io thermochromic materials, photoresists, electrorhe-ological materials, 12 film patteming, recording materials, 4 lithium battery, semiconductors, printing materials, inks, corrosion inhibitors, adhesives, drugs, detecting viable cells, treatment of Alzheimer s disease  

---

Rosolic acid, aurin, corallin, corallinphthalein, 4,4 -dihydroxy-fuchsone, 4,4 -dihydroxy-3-methyl-fuchsone (indicator) dissolve 0.5 g in 50 mL alcohol and dilute with water to 100 mL. Salicyl yellow (indicator) see alizarin yellow GG. 

Rosmarin, m. rosemary, -ol, n. rosemary oil. Rosolsaure, /. rosolic acid. 

The triarylmethane dyes are broadly classified into the triphenyl-methanes (Cl 42000-43875), diphenylnaphthylmethanes (Cl 44000-44100), and miscellaneous triphenylmethane derivatives (Cl 44500-44535). The triphenylmethanes are classified further on the basis of substitution in the aromatic nuclei, as follows (1) diamino derivatives of triph-enyhnetliane, i.e., dyes of the malachite green series (Cl 42000-42175) (2) triamino derivatives of triphenylmethane, i.e., dyes of the fuchsine, rosani-line. or magenta series (Cl 42500-42800) (3) aminohydroxy derivatives of triphenylmethane (Cl 43500-43570) and (4) hydroxy derivatives of triphenylmethane, i.e., dyes of the rosolic acid series (Cl 43800-43875). Monoaminotriphcnylmcthancs arc known but they arc not included in the classification because they have little value as dyes. 

Reaction XL. (a) Condensation of a Phenol with a Methane Carbon Atom. (A., 194, 123 196, 77 B., 28, R., 743.)—Phenols can be condensed with compounds which can yield a nuclear carbon, to give dyes of the rosolic acid series. The fewco-compound—tri-hydroxytriphenyl car-binol—first formed, is unstable and immediately yields the dyestuff, no oxidising agent being necessary. In this respect these compounds differ from the analogous rosaniline compounds (see p. 382). 

Rosolic acid (methyl aurin), another important member of this series, is prepared by oxidising a mixture of phenol and o- and p-cresols with arsenic acid and sulphuric acid. 1 mol. of each of the cresols and 1 mol. of phenol react, the methyl carbon of the p-cresol molecule serving as a nuclear carbon. 

A similar constitution may be accepted for rosaniline and rosolic acid. 

Only a few natural dyestuffs (indigo, alizarin, and purpurin) have been prepared synthetically, but the number of artificial dyestuffs is very large. Some of these, especially the phthalei ns and rosolic acid, seem to approach the natural dyestuffs in constitution, but the greater number belong to special classes, which are without analogue in either the animal or the vegetable kingdom. 

The honour of preparing the first colouring-matters from products of dry distillation belongs to von Reichenbach (pittacal from wood-tar, 1832), and to Runge (rosolic acid from coal-tar, 1834) [1]. 

In 1861 Laurent and Castelhaz [8] patented the action of nitrobenzene on iron and hydrochloric acid, and this is evidently the first opening of the nitrobenzene process. In the same year the synthesis of rosolic acid was effected by Kolbe and Schmitt [9]. 

The rosolic acid described by Runge (1834) as obtained from the residue of crude phenol distillation is probably identical with the body at present under consideration. 

---