2-Phenyl-1,3-dioxane, hydrolysis

The enamines derived from cyclic ketones give the normal alkylated products, although there is some evidence that unstable cycloadducts are initially formed (55b). Thus the enamine (28) derived from cyclohexanone and pyrrolidine on reaction with acrylonitrile, acrylate esters, or phenyl vinyl sulfone gave the 2-alkylated cyclohexanones (63) on hydrolysis of the intermediates (31,32,55,56). These additions are sensitive to the polarity of the solvent. Thus (28) in benzene or dioxane gave an 80% yield of the... 

Figure 1. Hydrolysis pH-rate profiles of phenyl acetate (lower) and a substituted 2-phenyl-l,3-dioxane (HND). Phenyl acetate profile constructed from data of Mabey and Mill (32), HND profile from data of Bender and Silver (33). Phenyl acetate reacts via specific-acid catalyzed, neutral, and base-catalyzed transformation pathways. The pseudo-first-order rate constant is given by Kobs = K(h+) [H+] + Kn + K(qh-) [0H—]. HND hydrolyzes only via an acid-catalyzed pathway the phenolate anion is some 867 times more reactive than its conjugate acid.

Some cyclic thioacetals have an A-SE2 hydrolysis mechanism,206 as do some 2-aryl-2-methyl-l,3-dithianes, except for the 4-NO2 derivative, which looks more A2-like.207 In 10 vol% dioxane/aqueous HC104 mixtures, reactive 2-aryl-2-phenyl-l,3-dithianes are believed to have an A-SE2 hydrolysis mechanism, whereas the least reactive ones have an A2 mechanism.130 Isothiocyanates are believed to hydrolyze by a mechanism that involves simultaneous proton transfer to nitrogen and attack of water at carbon in a cyclic transition... 

Yanovskaya and coworkers55 have reported rate constants for the alkaline hydrolysis of ethyl lruns,trans-4 -substi tuted 5-phenyl-2,4-pentadienoates in 60% aqueous dioxan giving the values X, log t, H, -2.60 Cl, -2.23 Br, -2.31 N02, -1.83 OMe, -2.61 NMe2, —3.00. Correlation with the CR equation gave as the best regression equation ... 

Bender ML, Silver MS (1963) The hydrolysis of substituted 2-phenyl-1,3-dioxane. J Am Chem Soc 85 3006-3010... 

Fig. 12. First-order rate coefficients for the hydrolysis of weakly basic esters, as a function of acid concentration. Data for phenyl and methyl trifluoroacetates in HCIO, in 70% dioxan-water at 0°C (from refs. 89 and 90). and for o-nitrophenyl hydrogen oxalate in aqueous HCI at 25.5°C (from ref. 171 corrected for the reaction of the anion using pA", = 0.35).

Figure 4. Bronsied plot of the logarithm of the general base catalyzed hydrolysis rate constants vs. the p/C of the conjugate acids of the oxygen and nitrogen bases (buffers) for phenyl tris-(2-methoxyethoxy)silane ( ) and phenyl bis-(2-methoxyethoxy)silanol ( ) in aqueous solution at 30 C. and for tert-butyldimethyl-3-nitrophenoxysilane ( ) in 70% water/dioxane at 37°C.

Hydrolysis of 2-Methyl-2-benzyl-l,3-dioxolane. A sample of 1 gram of the dioxolane was suspended in 20 ml. of 50% dioxane which contained enough HC1 to make it 0.5N. The suspension was heated at 60°C. and became a clear solution in 1-2 minutes. Total heating time was 5 minutes. The product was identified as 3-phenyl-2-propanone by the properties of its 2,4-dinitrophenylhydrazone and semicarbazone derivatives. 

Solvent D KIE in the acid-catalysed hydrolysis of some iV-phenyl-4-substituted-benzohydroxamic acids (equation 276), using either H2SO4 or D2SO4 in 20/80 dioxane-water medium, have been observed to be equal (Table 4)536. 

Other donor molecules react with phosphonitrilic compounds. Dioxane is said to facilitate the depolymerization of the high polymer (63) and of the phenyl derivatives (13). Acetone forms complexes with the amino acid derivatives of the tetramer (see p. 128 in ref. 3). It is possible that ether acts as a catalyst for the hydrolysis of the trimeric chloride. The effect of these solvents is subtle, since the solubilities of the trimeric chloride in ether, in pyridine, and in dioxane show no sign of any specific chemical interaction. 

Yanovskaya and coworkers have reported rate constants for the alkaline hydrolysis of ethyl -substituted 5-phenyl-2,4-pentadienoates in 60% aqueous dioxan... 

The solvents suitable for use in the hydrolysis of 1-phenyl-2,2-dialkoxypropanes are those which dissolved well both the 1-phenyl-2,2-dialkoxypropanes and the water and also which are substantially inert against the hydrolysis. IVpical examples of these solvents are lower alcohols such as methanol, ethanol, propanol, and butanol ethers such as dioxane and tetrahydrofuran and carboxylic acids such as acetic acid and propionic acid. Of these examples, the use of methanol, ethanol, propanol, butanol, dioxane, and tetrahydrofuran are particularly desirable. Furthermore, slightly water-soluble alcohols such as pentanol, hexanol, and heptanol can be used as a solvent in combination with dioxane and tetrahydrofuran. 

A mechanism that explains some of the more important observations in the acid-catalyzed hydrolysis of epoxides 49a-d is outlined in Scheme 15. The cis/trans diol product ratios from the acid-catalyzed hydrolysis of 49a-c, which have either hydrogen- or electron-donating groups in the para position of the phenyl ring, are 74 26, 83 17 and 65 35, respectively. An intermediate carbocation 52a is trapped by azide ion in the acid-catalyzed hydrolysis of 49a and the rate constant for reaction of 52a with water in 10 90 dioxane-water solvent is estimated, by the azide clock technique, to be 1.7 x 108 s 1. Azide ion also traps an intermediate 52b in the acid-catalyzed hydrolysis of 49b, but somewhat less efficiently. The rate constant ks for reaction of 52b with solvent is estimated to be 2 x 109 s-1. The somewhat greater reactivity of 52b compared to that of 52a is consistent with the observation that... 

The enantiomerically pure perhydro-l,3-oxazine-2,6-dione (72 R = menthyl Ar = 4-methoxyl-phenyl) reacts with benzaldehyde to give the benzylidene derivative (73). This compound shows high diastereofacial selectivity ( 98%) when used as either an oxadiene, or as a Michael acceptor. For example, with 2-methoxypropene, followed by thermolysis of the adduct in boiling 1,4-dioxane, it affords the ketoaldehyde (74) and with ethyl magnesium bromide it gives the adduct (75), acidic hydrolysis of which yields the chiral acid (76) (Scheme 15) <92CL485,92CPB1972). 

Kern et al. found that, contrary to most heterocyclic monomers, TXN can be copolymerized with styrene (St) to random copolymers 149). Since that time the cationic copolymerization of TXN (and also DXL) with styrene has been studied by several groups but unfortunately GPC analysis was not commonly used and the only proof that copolymers were formed are based on solubility studies and on the presence of 4-phenyl-1,3-dioxane among the hydrolysis products of the products. Let us summarize the facts concerning TXN-styrene copolymerizations ... 

The presence of 4-phenyl-1,3-dioxane in the polymerizing mixture and among the copolymer hydrolysis products indicates that styrene is incorporated into the growing polyTXN chain and that attack occurs on the P-carbon atom of the double bond ... 

In essentially the same way 4-phenyl-1,3-dioxane may be formed by hydrolysis provided that St units are connected at both sides to oxymethylene units ... 

Aryloxybutyramides (effectively amido derivatives at the benzylic position in phenyl isopropyl ether) readily formed from 2-bromo-iso-butyramide and a variety of phenoxides in dioxane undergo the Smiles rearrangement in dimethylformamide containing 1,3-dimethyltetrahydropyrimidin-2(1H)-one (DMPU) solution and sodium hydride to form substiuted acetanilides with yields in the range 60-90%. Thence by hydrolysis aromatic amines are formed in good yields (ref. 168). 

Combine and extend the concept of the generalized physical properties approach and Guggenheim s method to the case of an irreversible second-order reaction. Use your analysis to solve a problem adapted from one composed by J. W. Moore and R. G. Pearson Kinetics and Mechanisms, 3rd ed., p. 78, Wiley, New York, 1981]. Note that most of the data were recorded at time t and at time f -f 110 s and that stoichiometric quantities of reactants were used in the experiment. You may find it useful to group your time terms such that they appear in the form (f -I- A) V — f K, where A, is the measured property at time t = f -I- A and A is the measured property at time t. S. W. Tobey [/. Chem. Educ., 39, 473 (1962)] studied the rate of hydrolysis of phenyl-m-nitrobenzoate in a 50% aqueous dioxane solution at 25°C. 

The question of the high exolendo rate ratio was examined with exo- and endo-2-phenyl-2-norbornanol. The tertiary and benzylic 2-phenylnorbornyl cation is classical, as evidenced by its NMR spectrum. Since the relative rates of hydrolysis of exo- and endo-2-phenylnorbornyl p-nitrobenzoate in 60% aqueous dioxane at 50°C are 140, and the reactions proceed by rate-determining formation of classical carbonium ions. Brown concluded that the exo-endo rate ratio of 340 for norbornyl brosylates does not require assisted ionization of exo-norbornyl brosylate. ... 

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