Yield acetal

Oxidation. Acetaldehyde is readily oxidised with oxygen or air to acetic acid, acetic anhydride, and peracetic acid (see Acetic acid and derivatives). The principal product depends on the reaction conditions. Acetic acid [64-19-7] may be produced commercially by the Hquid-phase oxidation of acetaldehyde at 65°C using cobalt or manganese acetate dissolved in acetic acid as a catalyst (34). Liquid-phase oxidation in the presence of mixed acetates of copper and cobalt yields acetic anhydride [108-24-7] (35). Peroxyacetic acid or a perester is beheved to be the precursor in both syntheses. There are two commercial processes for the production of peracetic acid [79-21 -0]. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or osone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde (36). Peracetic acid can also be formed directiy by Hquid-phase oxidation at 5—50°C with a cobalt salt catalyst (37) (see Peroxides and peroxy compounds). Nitric acid oxidation of acetaldehyde yields glyoxal [107-22-2] (38,39). Oxidations of /)-xylene to terephthaHc acid [100-21-0] and of ethanol to acetic acid are activated by acetaldehyde (40,41). 

The important chemical properties of acetyl chloride, CH COCl, were described ia the 1850s (10). Acetyl chloride was prepared by distilling a mixture of anhydrous sodium acetate [127-09-3J, C2H202Na, and phosphorous oxychloride [10025-87-3] POCl, and used it to interact with acetic acid yielding acetic anhydride. Acetyl chloride s violent reaction with water has been used to model Hquid-phase reactions. 

In the first step of the reaction, the acetoxylation of propylene is carried out in the gas phase, using soHd catalyst containing pahadium as the main catalyst at 160—180°C and 0.49—0.98 MPa (70—140 psi). Components from the reactor are separated into Hquid components and gas components. The Hquid components containing the product, ahyl acetate, are sent to the hydrolysis process. The gas components contain unreacted gases and CO2. After removal of CO2, the unreacted gases, are recycled to the reactor. In the second step, the hydrolysis, which is an equhibrium reaction of ahyl acetate, an acid catalyst is used. To simplify the process, a sohd acid catalyst such as ion-exchange resin is used, and the reaction is carried out at the fixed-bed Hquid phase. The reaction takes place under the mild condition of 60—80°C and ahyl alcohol is selectively produced in almost 100% yield. Acetic acid recovered from the... 

A process to convert butenes to acetic acid has been developed by Farbenfabriken Bayer AG (137) and could be of particular interest to Europe and Japan where butylenes have only fuel value. In this process a butane—butylene stream from which butadiene and isobutylene have been removed reacts with acetic acid in the presence of acid ion-exchange resin at 100—120°C and 1500—2000 kPa (about 15—20 atm) (see Acetic acid and its derivatives, acetic acid). Both butenes react to yield j -butyl acetate which is then oxidized at about 200°C and 6 MPa (about 60 atm) without catalyst to yield acetic acid. 

Poethke shows that on alkaline hydrolysis protoveratrine yields acetic, Z-methylethylacetic and methylethylglycollic acids and the alkamine protoverine. It is therefore a triacyl ester of protoverine. 

In the chymotrypsiii mechanism, the nitrophenylacetate combines with the enzyme to form an ES complex. This is followed by a rapid second step in which an acyl-enzyme intermediate is formed, with the acetyl group covalently bound to the very reactive Ser . The nitrophenyl moiety is released as nitrophenolate (Figure 16.22), accounting for the burst of nitrophenolate product. Attack of a water molecule on the acyl-enzyme intermediate yields acetate as the second product in a subsequent, slower step. The enzyme is now free to bind another molecule of nitrophenylacetate, and the nitrophenolate product produced at this point corresponds to the slower, steady-state formation of product in the upper right portion of Figure 16.21. In this mechanism, the release of acetate is the rate-llmitmg step, and accounts for the observation of burst kinetics—the pattern shown in Figure 16.21. 

Yb(OTf)3, MeOH, 0-25°, 92-99% yield. Acetates, benzoates, THP, TBDMS, TBDPS, and MEM ethers are not affected by this reagent. ... 

The final step is the reaction hetween acetyl iodide and methyl alcohol, yielding acetic acid and the promotor ... 

Ketene further reacts with one mole acetic acid, yielding acetic anhydride ... 

A problem often encountered in the oxidation of primary alcohols to acids is that esters are sometimes produced as by-products. For example, oxidation of ethanol yields acetic acid and ethyl acetate ... 

Aldehydes and ketones react reversibly with 2 equivalents of an alcohol in the presence of an acid catalyst to yield acetals, R2C(OR )2, sometimes called ketals if derived from a ketone. Cyclohexanone, for instance, reacts with methanol in the presence of HCl to give the corresponding dimethyl acetal. 

Aldehydes and ketones react with thiols to yield thioacetals just as they react with alcohols to yield acetals. Predict the product of the following reaction, and propose a mechanism ... 

The completion of the synthesis of key intermediate 86 only requires some straightforward manipulations. Differential protection of the two hydroxyl groups in 123 can be easily achieved. Selective silylation of the primary hydroxyl with ieri-butyldiphenylsilyl chloride provides, after /ert-butyldimethylsilylation of the remaining secondary hydroxyl, compound 124 (95% overall yield). Acet-onide protecting groups can usually be removed under acidic conditions, and the one present in 124 is no exception. Treatment of a solution of 124 in CFhC MeOH (1 1) at 0°C with CSA... 

Ring-opening of diastereomerically pure vinylaziridine 131, prepared by azir-idination of butadiene with 3-acetoxyaminoquinazolinone 130 [52], yielded acetate 132 with inversion of configuration, together with amino alcohol 133 with retention (Scheme 2.34) [53]. The formation of 133 can be explained by assuming participation by the quinazolinone carbonyl oxygen, which produces an intramolecular reaction with the aziridine carbon with retention of configuration. 

Ans. One can add sodium acetate and hydrochloric acid. The reverse of the ionization reaction occurs, yielding acetic acid ... 

Grignard reagents can also act as sources of negative carbon in displacement reactions, e.g. in the synthetically useful reaction with triethoxymethane (ethyl orthoformate, 58) to yield acetals (59) and, subsequently, their parent aldehydes (60) ... 

The formation of oxaloacetic acid by dehydrogenation implies that this acid may be dissimilated by two mechanisms. It is known (62), (114) that oxaloacetic acid is subject to decarboxylation under acid conditions, and that higher pH is favorable to its stability. Thus, alkaline media enable the add to remain unchanged long enough to be split, yielding acetate and oxalate, while acidic media cause decarboxylation. 

These considerations allow for a cyclic mechanism to occur in the formation of oxalic acid, where oxaloacetic acid yields either oxalate and acetate, which may be reoxidized, or pyruvate, which will then in turn yield acetate. This is illustrated in the following phase sequence of oxalate formation by these organisms ... 

A mixture of Pt(ll) and metallic Pt in an aqueous medium was shown to oxidize ethane to yield acetic and glycolic acids. A series of deuterium-exchange processes enabled a complex mechanism to be elucidated metallic platinum catalyzes the oxidation of intermediate alcohols to acid products, whereas the Pt(ll) salt activates the initial alkene (Scheme 7X29... 

Another example is that of a-acetoxystyrene (7.13), which yields acetic acid and acetophenone (7.14) upon hydrolysis. This compound is quite stable... 

Anodic regioselective acetamidosulfeny-lation of alkenes is similarly achieved by oxidation of diphenyldisulfide in acetonitrile [81]. Cyclic enamines, which are intermediates in the oxidation of cyclic N-methoxycarbonyl amines, react in aqueous acetonitrile that contains chloride ions to a-hydroxy- 8-chloro compounds via intermediate chloronium ions [82]. Enolethers undergo a regioselective azidomethoxyla-tion to yield acetals of a-azido carbonyl compounds upon electrolysis in methanol containing sodium azide [83]. The reaction proceeds possibly via addition of an anodicaUy generated azide radical. 

Chemical/Physical. Oxidation in air yields acetic acid (Windholz et ah, 1983). In the presence of sulfuric, hydrochloric, or phosphoric acids, polymerizes explosively forming trimeric paraldehyde (Huntress and Mulliken, 1941 Patnaik, 1992). In an aqueous solution at 25 °C, acetaldehyde is partially hydrated, i.e., 0.60 expressed as a mole fraction, forming a gem-diol (Bell and McDougall, 1960). Acetaldehyde decomposes at temperatures greater than 400 °C, forming carbon monoxide and methane (Patnaik, 1992). 

This enzyme [EC 3.5.1.29] catalyzes the hydrolysis of 2-(acetamidomethylene)-succinate to yield acetate, succinate semialdehyde, carbon dioxide, and ammonia. 

This enzyme [EC 2.3.1.35], also known as ornithine ace-tyltransferase, and ornithine transacetylase, catalyzes the reversible reaction of A -acetyl-L-ornithine with L-gluta-mate to produce L-ornithine and A-acetyl-L-glutamate. This protein also exhibits a low hydrolysis activity (about 1% of that of the transferase activity) of iV -acetyl-L-ornithine to yield acetate and L-ornithine. This enzyme is not identical with A-acetylglutamate synthase [EC 2.3.1.1]. 

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