Ortho-acids 464 -compounds

The trivial name acetoxy is retained for the CH3—CO—O— group. Compounds of the type R C(0R )3 are named as R esters of the hypothetical ortho acids. For example, CH3C(OCH3)3 is trimethyl orthoacetate. 

TABLE 5 Comparing the Shaping of a Poly(ortho ester) Compound by Flux-Mixing with 5 wt% Stearic Acid... 

Substituent effects on the A,u I reaction have been studied by Bender and Chen55. These authors measured the rates of hydrolysis of a series of 4-substituted 2,6-dimethylbenzoates in 9.70 M sulphuric acid at 25°C, and found that the values for the first-order coefficients with 4-methoxy, 4-methyl, 4-unsubstituted and 4-bromo-compounds (5.0, 0.37, 0.033 and 0.01 x I0 4 sec-1, respectively) are satisfactorily correlated by the Hammett equation, following cr+ with a slope p = —3.22. Since the esters are not fully protonated in 9.70 M H2SOj, part of this factor is due to the effects of the 4-substituent on the protonation equilibrium, p for the protonation of substituted benzoic acids is about — l35, but is likely to be considerably smaller for di-ortho-substituted compounds, since the conjugative interaction of the p-substituents with the protonated carboxyl group requires coplanarity with the ring. 

A considerable rise of temperature takes place on mixing sulphuric acid with water it is not improbable that the first anhydride of the true ortho-acid is formed the compound of the formula H2S0,.H20, which may be 0=S=(0H)4, melts at 8°. The point of maximum contraction of a mixture of sulphuric acid and water occurs when the proportion corresponds to H2S04.2H20 this is possibly S(OH)fi, but it does not easily solidify. Water can be withdrawn from sulphuric acid by distilling it with phosphorus pentoxide, when sulphuric anhydride is formed and distils over. 

The acid which is produced finally by the oxidation of phosphorus in the presence of sufficient water and after heating has probably the constitutional formula OP(OH)s (see p. 59). The term ortho, in accordance with Graham s description, was applied to ordinary phosphoric acid. Later, on the hypothesis of the quinquevalent nature of phosphorus, it was considered that the hypothetical acid P(OH)5 would, strictly speaking, be the ortho acid. However, the present theories of valency do not indicate the possible existence of such an acid, but rather that OP(OH)3 should be the most highly hydroxylated compound. 

The oxy-acids of phosphorus and their derivatives are defined as compounds which contain both P — OH and P = 0 functions (7-9,12). Ortho-phosphoric acid, phosphorus acid, and hypophosphorous acid are well-known as the oxy-acid compounds that contain three, two, and one OH... 

Anthranilic Acid.—Nitration of toluene and subsequent oxidation yields largely the para and ortho compounds. A fact of interest in connection with these nitro benzoic acids is that the ortho acid is sweet while the meta and para acids are bitter. On reduction with tin and... 

Dimethoxyphenyl tellurium trichloride or bis [3,4-dimethoxyphenyl] ditellurium were nitrated, the ortho-miro compound reduced to the 1,2,5-oxatellurazole with hypophospho-rous acid, and this heterocyclic compound converted to the 5,6-dimethoxy-l, 3-benzotellur-azole . 

Hydroxylations of aromatic rings are also achieved via transient esters that are easily hydrolyzed in situ to the corresponding phenols. In this way, anisole and diphenyl ether are oxidized by peroxytrifluoroacetic acid to predominantly ortho-hydroxy compounds in low yields (equation 147) [1118]. 

Heating in dilute acid removes the sulfonic acid group (Section 15.12). Using a sulfonic acid group to block the para position is a method commonly employed to synthesize high yields of ortho-substituted compounds. 

Salicylic acid can be prepared by the oxidation of o-hydroxy-benzyl alcohol, by the fusion of o-toluenesulphonic acid and other ortho acids with potassium hydroxide, by heating with water the diazo compound formed from anthranilic acid. It can be obtained with a favorable yield when o-cresol is fused with potassium hydroxide and lead peroxide the latter compound oxidizes the methyl radical to carboxyl. A mixture of o- and p-hydroxybenzoic acid is obtained from phenol by the Tiemann-Reimer synthesis (507). 

Periodates are the metal salts of periodic acid [10450-60-9], The general formula of these compounds is M(I04)j, , where M is a metal ion having the valency x. Periodic acids occur in two forms the meta acid, HIO4, and the ortho acid, H5IO6, which is the dihydrate of meta acid. Periodic acid is a much weaker acid than perchloric acid and is reduced to iodic acid by nitrous and sulfurous acids. Potassium periodate [7790-21-8] is the only metal periodate of commercial use. It is used as an oxidizing agent and for colorimetric analysis of manganese. 

Use of nonaqueously prepared DEAE celluloses as Lewis bases offers potential for formation of metal ion complexes between transition metal ions such as Cu and Ni 2j formation of charge-transfer complexes with electron acceptor compounds such as ortho-and para-chloranils or bromanils and with other Lewis acid compounds such as BI3. 

Some early work on copolymer-compatibilized PPE-PPS blends is summarized in Arashiro et al. (1992). PPE-PPS blends have also been compatibilized through copolymer formation between citric acid-functionalized PPE (e.g., 162 parts) and PPS (e.g., 225-275 parts) in the presence of a multifunctional epoxy resin (0-17.5 parts) and a minor amount of PBT (25-50 parts) (Brown et al. 1997a) or in the presence of a epoxy-functionalized PO and a catalyst (Brown et al. 2001) or in the presence of a bifunctional cyclic ortho ester compound (Brown et al. 1998a). See also Dekkers (1989) and Inoue et al. (1990). Okabe et al. (1989) have prepared compatibilized blends comprising PPE-g-MA and amine-functionalized PPS in the presence of 4,4 -diphenylmethane diisocyanate coupling agent. 

---