Glycolic acetal aldehyde

Lead tetraacetate is used as a highly selective oxidizing agent in organic synthesis. This includes oxidation of glycols into aldehydes, preparation of cyclohexyl acetate, production of oxahc acid, and in structural analysis of sugars. 

CH3 Acetic aldehyde 1 1 CH2OH Glycolic aldehyde 1 1 CHO Glyoxal 1 ... 

Other aldehydes and related compounds have been reacted either alone or catalyzed with sulfuric acid, zinc chloride, magnesium chloride, ammonium chloride, or diammonium phosphate (94). Compounds such as l,3-bis(hydroxymethyl)-2-imidazolidone, glycol acetate, acrolein, chloroacetaldehyde, heptaldehyde, o- and p-chloro-benzaldehydes, furfural, p-hydroxybenzaldehyde, and m-nitrobenz-aldehyde all achieve the ASE by a bulking mechanism and not by low-level cross-linking. At weight gains of 15-25%, the highest ASE reported is 40%. 

Acetals and ketals of ethylene glycol are readily formed from bis-trimethylsilyl ethylene glycol, the aldehyde or ketone and trimethylsilyl triflate catalysis51 (equation 43). The reaction is quite selective for ketones over aldehydes (equation 44). 

In references dealing with the above mentioned procedure, using periodate as an oxidant and not using bromate, it is stated that formaldehyde, acetic aldehyde, glycolic acid, oxalic acid, formic acid, amlone dialdehyde, and glyoxal do not interfere. 

Thus from the sodium salt of glycolic acid (CH,OH. COOH), ethyl-glycolic acid (CH,OC,Hj.COOH), and a-lactic acid (CH3.CH(OH)COOH) the chief product obtained is acetic aldehyde, and it is quite possible that the production of hydrobenzoin and isohydrobenzoin from mandelic acid is due to the electrolytic reduction of the benzaldehyde originally formed. 

Synonyms Cinnamic aldehyde ethylene glycol acetal Cinncloval 2-Styryl-1,3-dioxolane 2-Styryl-m-dioxolane... 

Cinnamic acid, 3-phenyl propyl ester. See 3-Phenylpropyl cinnamate Cinnamic alcohol. SeeCinnamyl alcohol, Cinnamic aldehyde. See Cinnamal Cinnamic aldehyde ethylene glycol acetal. See Cinnamaldehyde ethylene glycol acetal Cinnamic chloride. See Cinnamoyl chloride Cinnamol. See Styrene Cinnamomum camphora. See Camphor Cinnamomum camphora oil. See Camphor (Cinnamomum camphora) oii Cinnamomum cassia. See Cinnamon (Cinnamomum cassia) extract Cinnamon (Cinnamomum cassia) Cinnamon (Cinnamomum cassia) oii... 

Methylprotocatechualdehyde Methylprotocatechuic aldehyde. See Vanillin Methyl Proxitol. See Methoxyisopropanol Methyl Proxitol Acetate. See Propylene glycol methyl ether acetate 4-Methyl-2-proyl-1,3-dioxolane. See Butyraldehyde propylene glycol acetal... 

The oxidation of terminal alkenes with an EWG in alcohols or ethylene glycol affords acetals of aldehydes chemoselectively. Acrylonitrile is converted into l,3-dioxolan-2-ylacetonitrile (69) in ethylene glycol and to 3,3-dimetho.xy-propionitrile (70) in methanol[28j. 3,3-Dimethoxypropionitrile (70) is produced commercially in MeOH from acrylonitrile by use of methyl nitrite (71) as a unique leoxidant of Pd(0). Methyl nitrite (71) is regenerated by the oxidation of NO with oxygen in MeOH. Methyl nitrite is a gas, which can be separated easily from water formed in the oxidation[3]. 

Diols that bear two hydroxyl groups m a 1 2 or 1 3 relationship to each other yield cyclic acetals on reaction with either aldehydes or ketones The five membered cyclic acetals derived from ethylene glycol (12 ethanediol) are the most commonly encoun tered examples Often the position of equilibrium is made more favorable by removing the water formed m the reaction by azeotropic distillation with benzene or toluene... 

Ketones and aldehydes react with ethylene glycol under acidic conditions to form 1,3-dioxolanes (cychc ketals and acetals) (eq. 7). 

The primary and secondary alcohol functionahties have different reactivities, as exemplified by the slower reaction rate for secondary hydroxyls in the formation of esters from acids and alcohols (8). 1,2-Propylene glycol undergoes most of the typical alcohol reactions, such as reaction with a free acid, acyl hahde, or acid anhydride to form an ester reaction with alkaU metal hydroxide to form metal salts and reaction with aldehydes or ketones to form acetals and ketals (9,10). The most important commercial appHcation of propylene glycol is in the manufacture of polyesters by reaction with a dibasic or polybasic acid. 

Acetals andKetals. Acetals of 1,3-diols are prepared by refluxing the diol with the aldehyde in the presence of an acid catalyst, even in an aqueous medium. The corresponding ketals are more difficult to prepare in aqueous solution, but cycHc ketals of neopentyl glycol, eg, 2-butyl-2-ethyl-5,5-dimethyl-l,3-dioxane (3), can be prepared if the water of reaction is removed azeotropicaHy (34). 

Carbonyl Compounds. Cychc ketals and acetals (dioxolanes) are produced from reaction of propylene oxide with ketones and aldehydes, respectively. Suitable catalysts iaclude stannic chloride, quaternary ammonium salts, glycol sulphites, and molybdenum acetyl acetonate or naphthenate (89—91). Lactones come from Ph4Sbl-cataly2ed reaction with ketenes (92). 

Vanillin, being an aldehyde, is able to form acetals and hemiacetals. Therefore, in flavor formulations using high concentrations of vanillin in conjunction with carriers such as propylene glycol, a glc analysis often shows a reduced vanillin peak after storage of the compounded flavor, and the presence of new peaks indicating acetal formation. Addition of about 0.5% of water to the formula reverses the reaction, ie, there is a reduction of acetal, and the reappearance of vanillin peaks. 

Schauwecker, that when citronellal acetal is oxidised by permanganate, there is formed the acetal of the semi-aldehyde of j8-methyladipic acid and a glycol. The indistinct melting-points observed in citronellal derivatives (for example in the semi-carbazone) can also thereby be explained. It would appear that commercial citronellal contains the two isomeric forms in varying proportions. 

Show all the steps in the acid-catalyzed formation of a cyclic acetal from ethylene glycol and an aldehyde or ketone. 

---