Salicylic acid aldehyde

That the oil contains the following constituents, Z-a-pinene, d-a pinene, Z-limonene, Z-borneol, bornyl acetate and other esters of bomeol, Z-camphor, cineol, salicylic acid, aldehydes, formic, acetic, butyric ( ) and isovaleric acids, a non-volatile acid or lactone, and a blue constituent of high boiling-point. 

Action of sodium hydroxide. Does not undergo the Cannizzaro reaction. It dissolves in dil. NaOH solution, giving a yellow solution from which the aldehyde is precipitated unchanged on acidification. If heated with cone. NaOH solution, salicylaldehyde slowly undergoes atmospheric oxidation to salicylic acid. 

Fig. 8.6. pH-Rate profile for release of salicylic acid fiom benz-aldehyde disalicyl acetal. [Reproduced firom E. Anderson and T. H. Fife, J. Am. Chem. Soc. 95 6437 (1973) by permission of the American Chemical Society.]... 

Phenolic resins were the first totally synthetic plastics invented. They were commercialized by 1910 [I]. Their history begins before the development of the structural theory of chemistry and even before Kekule had his famous dreams of snakes biting their tails. It commences with Gerhardt s 1853 observations of insoluble resin formation while dehydrating sodium salicylate [2]. These were followed by similar reports on the behavior of salicylic acid derivatives under a variety of reaction conditions by Schroder et al. (1869), Baeyer (1872), Velden (1877), Doebner (1896 and 1898), Speyer (1897) and Baekeland (1909-1912) [3-17]. Many of these early reports appear to involve the formation of phenolic polyesters rather than the phenol-aldehyde resins that we think of today. For... 

Technically important dyes are salicylic acid derivatives that function as chrome mordant dyes for wool. Thus Cl Mordant Blue 1 (6.187) is made by the aldehyde synthesis from 2,6-dichlorobenzaldehyde and 2-hydroxy-3-methylbenzoic (o-cresotinic) acid in concentrated sulphuric acid. Oxidation of the leuco base is achieved by the addition of sodium nitrite. On wool the product, which is isolated as the sodium salt, is a dull maroon colour, changing to a bright blue on treatment with a chromium salt. Some dyes of this type, such as Cl Mordant Violet 1 (6.188), also contain a basic group. This compound is also prepared by the aldehyde route. 

Carreira and co-workers reported novel Ti(lV) complexes 69 derived from Ti(0 Pr)4, tridentate ligands 67, and salicylic acids such as 68. The complexes serve as competent catalysts for the addition of the methyl acetate-derived silyl ketene acetal to a large range of aldehydes (Eqs. 8B2.16 and 8B2.17) [22]. The salient features of this system include the wide range of functionalized aliphatic and aromatic aldehydes that may be used the ability to carry out the reaction with 0.2-5 mol % catalyst-loading and experimental ease with which the process is executed (Table 8B2.8). Thus the reaction can be carried out at -10 to 0°C, in a variety of solvents, without recourse to slow addition of reagents. The adducts from the catalytic reaction were isolated with excellent enantiopurities up to 99% ee. The original catalyst-preparation... 

Hydroxy-benzoic acids are characterized by the presence of a carboxyl group substituted on a phenol. Examples include /7-hydroxybenzoic acid (1.4), gallic acid (1.5), protocathechuic acid (1.6), salicylic acid (1.7) and vanillic acid (1.8). Related are hydroxybenzoic aldehydes, such as vanillin (1.9), which have an aldehyde group in stead of a carboxyl group. 

A typical case, one of the earliest investigated, is that of salicylic aldehyde saturated with salicylic acid for the organic substance. If X aq., the variable aqueous solution, is potassium chloride, the e.m.f. changes from + 137 mv. to —32 mv. as the salt concentration is increased from N/6,250 to 2-5 N, the e.m.f. s being established at once and remaining practically constant up to at least two hours. As the concentration of the salt increases, the organic phase, which is acid in reaction, becomes less positive to the water. 

From Phenol Alcohols and Phpnol Aldehydes.— The phenol alcohols and phenol aldehydes will of course yield phenol acids on oxidation. Reactions for these need not be written as they have been given in general at various times. Salicylic acid or ortho-hydroxy benzoic acid has the constitution assigned to it as proven by the syntheses just discussed. 

Esters.— The simplest class of compounds present in essential oils are the esters or ethereal salts (p. 140). In our early discussion of these compounds in the aliphatic series it was stated that the odor and flavor of common fruits is probably due to ester compounds and that certain empirical mixtures of esters are used as artificial fruit essences. Artificial apple essence, for example, may be prepared by mixing certain proportions of ethyl nitrite, ethyl acetate and amyl valerate with chloroform, aldehyde and alcohol. An example of an essential oil which consists of a single ester is oil of wintergreen. vAdxh is the methyl ester of salicylic acid, ortho-hydroxy benzoic acid (p. 714). 

Hydration is not the only way in which an aldehyde intennediate may be protected against reduction the aldehyde may be converted in situ into a borate complex of the hydrate [28-31] or into a bisulfite addition complex [32,33]. There is compelling evidence that borate complexes, such as II in Eq. (6), in the case of salicylic acid reduction, are intermediates. The salt (II) has been isolated and characterized [31], and in the presence of proton donors it undergoes four-electron reduction a plausible mechanism is suggested ... 

The reduction of salicylic acid to salicylaldehyde is believed to have been practiced commercially in India and the USSR [27]. Two-phase systems may also be used so that the aldehyde is rapidly removed from aqueous solution by extraction into an organic phase [28-30]. It was shown that correct choice of buffer and a two-phase system allows reductions of aromatic acids to aldehydes in acceptable yield (>50%) in addition, the likelihood of such success is greater with the lower pKa value of the acid and lower E1/2 value for reduction of the corresponding methyl ester [30]. 

The Electrolytic Preparation of Salicylic Aldehyde from Salicylic Acid (1)... 

Salicylic aldehyde is prepared electrolytically by the reduction of salicylic acid (sodium salt) to the aldehyde. The ordinary type of diaphragm cell is used with a mercury cathode, using boric acid and sodium sulfate as catholyte. A current density of 6 amp. per sq. dm. is used, and the temperature is kept between 15° and 18° by means of a freezing mixture. The aldehyde is fixed as soon as formed by means of sodium bisulfite, and is recovered by means of acid hydrolysis and steam distillation. Up to the present stage of the process the best yield obtainable is 55 per cent. 

The purpose of this research was to study the experimental details for the preparation of salicylic aldehyde by the reduction of salicylic acid (sodium salt) electrolytically. 

In 1906 Dr. Hugo Weil patented a process (3) for the reduction of salicylic acid to salicylic aldehyde electrolytically. However, a number of important experimental details were omitted and no yields were stated. Two years later an article by Carl Mettler (4) appeared on the electrolytic reduction of salicylic acid (sodium salt) to salicylic aldehyde which was identical with the patent of Weil. 

When salicylic acid is reduced with the reducing agents commonly employed in the laboratory, the chief product is salicyl alcohol (5). This salicyl alcohol on treatment with acids is converted into a resinous product forming saliretin. The reduction, however, should take place in two stages, going first to the aldehyde and then to the alcohol, as follows ... 

Into the cell is then placed a solution of 15 g. sodium sulfate. 15. g. boric acid and 14 g. of salicylic acid (0.1 mole), just neutralized with the calculated amount of sodium hydroxide. The solution is then diluted to, 175 cc. All the boric acid not dissolve in this quantity of solution, but is kept in suspension by means of rapid mechanical stirring. The cell is placed in a cooling mixture, and when the temperature reaches 15° to 18° the current is turned on. A temperature of 15° to 18° is maintained throughout the experiment. A current of 3 amp. (6 amp. per sq. dm.) is then passed through the solution for a period of 1 hr. 55 min., which is slightly more than the calculated amount (5.4 amp.-hr.) necessary to reduce the salicylic acid to salicylic aldehyde. During the electrolysis 20 g. sodium bisulfite are added at the rate of about 1.5 g. every 10 min. It has been found best not to begin the addition of the sodium bisulfite until the electrolysis has been started about 5 min, since the bisulfite reduced to sulfur when added to soon, or too rapidly thereafter. 

The salicylic aldehyde distills over as a very pale yellow oil, heavier than water, and collects at the bottom of the received. The steam distillate is then extracted with ether, the extract treated with NaHC02 to neutralize any acid which distills over, then dried over Na2S04 and distilled. The residual liquor after steam distillation always contains some resin (0.2-2.0 g.) It is filtered hot and allowed to cool, in order to recover any unused salicylic acid. In this experiment no salicylic acid i recovered. 

Yield of salicylic aldehyde 6.7 g., 55 per cent. Current efficienc the same. The yield was calculated on the total amount of salicylic acid started with. 

It is found that the use of sodium bisulfite materially increases the yield of salicylic aldehyde. Further, that the lower temperatures (15° to 18°) favor the yield of salicylic aldehyde. At higher temperatures less salicylic aldehyde is produced and more of the resinous product. Up to a current density of 8 amp./sq. dm. the yield of salicylic aldehyde is increased. Intermittent electrolysis or stirring after electrolysis is necessary for good current efficiency since a sodium amalgam is built up during the electrolysis. Increasing the time of electrolysis seems to increase the quantity of resin formed. Increasing the concentration of salicylic acid (sodium salt) has little or no effect. 

Tesh, K.S, Lowe, A. The Electrolytic Preparation of Salicylic Aldehyde from Salicylic Acid lYans. Electrochemical Society (1924) 45 37-48 Tindall, J., B, Process for Reduction of Nitro Hydroxy Compounds 1944-, US 2,347,621... 

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