Hydroxy aldehydes compounds, Mixed

Aldehydes that have a hydrogens react with themselves when mixed with a dilute aqueous acid or base. The resulting compounds, (3-hydroxy aldehydes, are referred to as aldol compounds because they possess both an aldehyde and alcohol functional group. 

S mthesis.—The carbohydrates have been prepared synthetically by oxidizing the poly-hydroxy alcohols. We have recently spoken of the mixed alcohol and aldehyde or mixed alcohol and ketone compounds which are formed by the oxidation of the tri-hydroxy alcohol glycerol. We have, also, just stated that the carbohydrates have been proven to be mixed poly-hydroxy alcohols and aldehydes or ketones. The compound just referred to, as produced by the oxidation of glycerol, is the simplest compound which has the character of a true sugar. Its composition is in accordance with the first of the general formulas, viz., CsHeOs or C H2nOn, and from the number of carbon atoms present it would be termed a triose. The oxidation of glycerol results in a mixture of two compounds, viz., an aldehyde alcohol and a ketone alcohol. 

Alcohol-aldehydes and -ketones.— If the hydroxyl group in hydroxy aldehydes and ketones is in the side chain instead of the ring then the compounds instead of being mixed phenol-aldehydes will be alcohol-aldehydes or -ketones c.g.,... 

Preparation of secondary (or tertiary) carbinols from pyridines and an aldehyde (or a ketone) in the presence of magnesium or aluminum and mercuric chloride is known in pyridine chemistry as the Emmert reaction. 7 70 For example, dimethyl-2-pyridylcarbinol is obtained in this way from pyridine and acetone. When a mixture of pyridine and acetone is subjected to an electrolytic reduction in dilute sulfuric acid at lead electrodes, a mixture of two main products results, namely, 2-(2-hydroxy-2-propyl)-3-piperideine and 4-(2-hydroxy-2-propyl)piperidine. Analogous compounds are obtained with the use of methyl ethyl ketone as the reactant. The mixed electrolytic reduction of 2-methylpyridine and acetone affords 2-(2-hydroxy-2-propyl)-6-methyl-3-piper ideine (74) and 2-methyl-4-(2-hydroxy-2-propyl)-piperidine.71... 

Chloral.—Chloral, or tri-chlor acet-aldehyde, was first prepared by Liebig in 1832 by the chlorination of alcohol as above. It may also be obtained by the direct action of chlorine upon acet-aldehyde. It is an oily liquid with a sweet suffocating odor. It boils at 97.7°. It does not mix with water but on boiling with water it forms a hydrated compound which crystallizes in large clear crystals, readily soluble in water. This is known as chloral hydrate. The structure of chloral hydrate is probably that of an addition product, viz., a, chlorinated di-hydroxy alcohol. In this compound we have an exception to the general rule that two hydroxyl groups can not be linked to the same carbon atom. 

This group of mixed substitution products embracing compounds that are both aldehyde or ketone and acid in character are directly related to the mixed alcohol and acid compounds. If a hydroxy acid containing a primary alcohol group has this group oxidized the first product will be an aldehyde acid. Similarly if the alcohol group is a secondary one the oxidation product will be a ketone acid. 

Oxidation Products of Poly-hydroxy Alcohols.—In our study of the mixed poly-substitution products we considered the mixed alcohol-aldehyde and alcohol-ketone compounds and showed that they are intermediate oxidation products between poly-hydroxy alcohols and poly-basic acids (p. 228). To illustrate, when glycerol, tri-hydroxy propane, is oxidized the following products are obtained. 

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). 

Reagents formed in situ by reaction of r-BUjZnI with organic halides add to carbonyl compounds, such mixed zincates do not transfer their f-butyl group. a-Diazo- 3-hydroxy esters are formed by treatment of diazoacetic esters with Et Zn and aldehydes at low temperature. Allylzinc species derived from allylic esters add to carbonyl compounds to give a- or y-adducts according to the nature of the latter. ... 

Addition to carbonyl compounds. Isocyanic acid adds to the carbonyl group of many aldehydes (formaldehyde, chloral, trifluoroacetaldehyde) and ketones (s-dichlorotetrafluoroacetone, perfluorocyclobutanone) to give a-hydroxy isocyanates, a new class of compounds." Isocyanic acid and the carbonyl compound are mixed in... 

Synthesis of Phosphoric Acids and their Derivatives. - Among various approaches to phosphate esters the phosphorylation of phenols with dialkyl cyanophosphonate and the synthesis of triaryl phosphates under phase-transfer conditions are worthy of mention. Mixed trialkyl phosphates are also reported to be formed by brief cathodic electrolysis of the reaction of dialkyl phosphonates with aromatic aldehydes and ketones, presumably by rearrangement of the initial a-hydroxy compounds. Further reports have appeared of the generation of metaphosphates by various methods. The synthesis of analogues 1 of famesyl pyrophosphate which incorporate photoactive esters has been reported both compounds are competitive inhibitors of farnesyl transferase. 

A methyl substituted aromatic compound such as p-cresol can be best converted to the corresponding aldehyde such as p-hydroxy benzaldehyde by reacting a methanolic alkaline p-cresol in presence of a mixed co-acetate-Mn-acetate catalyst at a pressure of 8-lOkg/cm and temperature of 75-100°C in presence of air and a solvent such as piperidine or an amine (ammonia, triethylamine, etc.) that would yield approximately 80-90% of the aldehyde in about 16-18 hr. 

---