Phenols aldehydes

Phenol aldehydes are generally pleasant-smelling products. Some of them are particularly important as fragrance and flavor materials. Anisaldehyde and certain derivatives of protocatechu aldehyde (3,4-dihydroxybenzaldehyde) are well-known representatives. The monomethyl ether of protocatechu aldehyde, vanillin, is perhaps the most widely used flavor material. Other important derivatives of this aldehyde are veratraldehyde (dimethyl ether) and heliotropin (formaldehyde acetal derivative) they are not only used as fragrance and flavor substances, but also are intermediates in many industrial processes. 

Other industrial processes are the liquid-phase oxidation in the presence of cobalt catalysts [171] and the electrochemical oxidation in the presence of lower aliphatic alcohols via the corresponding anisaldehyde dialkyl acetal [172]. 

CgFIgOs, Mr 152.15, pi.3kPa 155 °C, df 1.056, is found in many essential oils and foods, but is often not essential for their odor or aroma. However, it does determine the odor of essential oils and extracts from Vanilla planifolia and V. tahitensis pods, in which it is formed during ripening by enzymatic cleavage of glycosides. 

Properties. Vanillin is a colorless crystalline solid mp 82-83 °C) with a typical vanilla odor. Because it possesses aldehyde and hydroxyl substituents, it undergoes many reactions. Additional reactions are possible due to the reactivity of the aromatic nucleus. Vanillyl alcohol and 2-methoxy-4-methylphenol are obtained by catalytic hydrogenation vanillic acid derivatives are formed after oxidation and protection of the phenolic hydroxyl group. Since vanillin is a phenol aldehyde, it is stable to autoxidation and does not undergo the Cannizzarro reaction. Numerous derivatives can be prepared by etherification or esterification of the hydroxyl group and by aldol condensation at the aldehyde group. Several of these derivatives are intermediates, for example, in the synthesis of pharmaceuticals. 

Production. Commercial vanillin is obtained by processing waste sulfite liquors or is synthesized from guaiacol. Preparation by oxidation of isoeugenol is of historical interest only. 

Mr 136.15, pi.85kPa 132 °C, df 1.1192, n 1.5703, occurs in many essential oils, often together with anethole. It is a colorless to slightly yellowish liquid with a sweet, mimosa, hawthorn odor. p-Anisaldehyde can be hydrogenated to anise alcohol and readily oxidizes to anisic acid when exposed to air. Synthetic routes to anisaldehyde start from p-cresyl methyl ether, which is oxidized e.g. by manganese dioxide or by oxygen or peroxy compounds in the presence of transition metal catalysts [170], [171]. 

C11H14O2, Mr 178.23, df 1.039-1.047, r 1.517-1.522, is a pale yellow liquid with licorice, anise note with slight fruity modification. It does not occur in nature. It can be prepared by condensation of anisaldehyde (see above) with propanal and selective hydrogenation of the resulting 2-methyl-3-(4-methoxyphenyl)-2-propenal. It fits well with flowery notes and is used in fine fragrances and cosmetics. 

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P-Hydroxy-a-naphthaldehyde, Equip a 1 litre three-necked flask with a separatory funnel, a mercury-sealed mechanical stirrer, and a long (double surface) reflux condenser. Place 50 g. of p-naphthol and 150 ml. of rectified spirit in the flask, start the stirrer, and rapidly add a solution of 100 g. of sodium hydroxide in 210 ml. of water. Heat the resulting solution to 70-80° on a water bath, and place 62 g. (42 ml.) of pure chloroform in the separatory funnel. Introduce the chloroform dropwise until reaction commences (indicated by the formation of a deep blue colour), remove the water bath, and continue the addition of the chloroform at such a rate that the mixture refluxes gently (about 1 5 hours). The sodium salt of the phenolic aldehyde separates near the end of the addition. Continue the stirring for a further 1 hour. Distil off the excess of chloroform and alcohol on a water bath use the apparatus shown in Fig. II, 41, 1, but retain the stirrer in the central aperture. Treat the residue, with stirring, dropwise with concentrated hydrochloric acid until... 

Phenol - aldehyde polymers. L. Baekland (1909) first demonstrated the possibilities of the reaction between phenol and formaldehyde from the commercial view point. Condensation in the presence of either... 

Because vanillin is a phenol aldehyde, it is stable to autooxidation and does not undergo the Cannizzarro reaction. Numerous derivatives can be prepared by etherification or esterification of the hydroxy group and by aldol condensation at the aldehyde group. AH three functional groups in vanillin are... 

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... 

Reasonable procedures for manufacturing resoles and novolacs are presented in subsequent sections. These procedures utilize the a concept known in the industry as programmed formaldehyde addition to avoid the problems mentioned above as well as aiding in control of the exothermic reactions resulting from the manufacture of the desired phenol-aldehyde products. These reactions are also extremely exothermic. 

High reactivity contaminants phenols, aldehydes, aromatics, amines, some sulfur compounds. 

Phenolic-aldehydic resin that remains permanently thermoplastic unless methylene groups are added. 

In the first century of "organic" chemistry much attention was given to the structures of carbogens and their transformations. Reactions were classified according to the types of substrates that underwent the chemical change (for example "aromatic substitution," "carbonyl addition," "halide displacement," "ester condensation"). Chemistry was taught and learned as transformations characteristic of a structural class (e.g. phenol, aldehyde) or structural subunit... 

Phenolics or phenol-aldehydes include the important commercial phenolic resin bakelite based on phenol and formaldehyde. A one-step process produces resol resin from more than one molecule of formaldehyde per phenol molecule. A two-step process uses an excess of phenol to produce novolacs - resins that have no reactive methylol groups and must be mixed with an aldehyde o undergo further reaction. 

Phenolic aldehydes Apply sample solution and then acidic 2,4-dinitro-phenylhydrazine solution, allow to react, dry and develop [15]... 

The synthesis of a large number of y-pyrones and y-pyranols from enamines has been brought about through the use of a wide variety of bifunctional molecules. These molecules include phenolic aldehydes (126,127), phenolic Mannich bases (128), ketal esters (129), and diketene (120-132). All of these molecules have an electrophilic carbonyl group and a nucleophilic oxygen center in relative 1,4 positions. This is illustrated by the reaction between salicylaldehyde (101) and the morpholine enamine of cyclohexanone to give pyranol 102 in a quantitative yield (127). 

Among the polymeric stabilizers may be listed poly-condensed polymers based on alkyl phenols, aldehydes, and ketones of the aliphatic series, where = 1 - 8 and R,R means alkyl [24], Na, K, Ca phenolates of poly-condensed polymers [25], and also products of epichlor-ide with one or more aliphatic amines C3—C30 [26]. 

Recognize a simple haloalkane, alcohol, ether, phenol, aldehyde, ketone, carboxylic acid, amine, amide, or ester, given a molecular structure. 

Examples of the protection of alkynes, carboxylic acids, alcohols, phenols, aldehydes, amides, amines, esters, ketones, and alkenes are also indexed on p. xvii. Section (designated with an A 15A, 30A, etc.) with protecting group reactions are located at the end of pertinent chapters. 

A blend of a polyoxyalkylene-polysiloxane copolymer and an alkoxy-lated phenol-aldehyde resin is useful as a demulsifier [1457, 1458]. 

The polyoxyalkylene units in the copolymer have a molecular weight below 500, and the polysiloxane units have 3 to 50 silicon atoms. The resin has a phenol/aldehyde ratio of 2 1 to 1 5 and an average molecular weight of 500 to 20,000 Dalton. The composition shows synergistic demulsification activity when compared with the individual components. The siloxane units can be either in blocks [979,980] of the polyoxyalkylene-polysiloxane copolymer or randomly distributed [728,729]. 

A Friedel-Crafts-type reaction of phenols under basic conditions is also possible. Aqueous alkaline phenol-aldehyde condensation is the reaction for generating phenol-formaldehyde resin.34 The condensation of phenol with glyoxylic acid in alkaline solution by using aqueous glyoxylic acid generates 4-hydroxyphenylacetic acid. The use of tetraalkylammonium hydroxide instead of sodium hydroxide increases the para-selectivity of the condensation.35 Base-catalyzed formation of benzo[b]furano[60]- and -[70]fullerenes occurred via the reaction of C60CI6 with phenol in the presence of aqueous KOH and under nitrogen.36... 

By substituting hydrogen cyanide for carbon monoxide it is further possible to prepare a very great variety of phenolic aldehydes and of their ethers. Usually the aldehyde group takes up the position para to the substituent already present. In this case the cuprous chloride is unnecessary. Since hydrogen cyanide and HC1 combine to form... 

Chemical instability of medicinal agents may take many forms, because the drugs in use today are of such diverse chemical constitution. Chemically, drug substances are alcohols, phenols, aldehydes, ketones, esters, ethers, acids, salts, alkaloids, glycosides, and others, each with reactive chemical groups having different stability characteristics. Chemically, the most frequently encountered destructive processes involve hydrolysis and oxidation. 

They are attacked by aromatic hydrocarbons, chlorinated solvents, ketones, esters, phenols, aldehydes, amines. 

Solvents Polysulfones resist acids at medium concentrations, alcohols, aliphatic hydrocarbons, greases, oils, gasoline, chlorine water They are attacked by aromatic hydrocarbons, chlorinated solvents, ketones, esters, phenols, aldehydes, amines Good to limited resistance against oils, greases, aliphatic hydrocarbons, certain alcohols Unsatisfactory against aldehydes, esters, ethers, ketones, aromatic hydrocarbons, chlorinated solvents, amines, certain alcohols, phenols. .. 

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