TBA formate

Fig. 24. Dependences of the initial rate of TBA formation and ratio of DIP/TBA on H3PMo,2O40 concentration in the hydration of butenes. TBA, lerl-butyl alcohol DIB, diisobutylene. 357 K, isobutylene/1-butene = 1/1 (molar). (From Ref. 163.)...

A positive reaction with TBA -formation of a fluorescent compound upon heating in 50% acetic acid- suggests the presence of peroxidic compounds in the polyenes. The TBA reactivity was most increased by the presence of ferrous ions. Little, if any, change in the reactivity occurred in solutions kept under normal lighting. The decrease in biological activity -about the same with all polyenes investigated- was the most in the UV-treated samples. Loss of UV absorption was observed after all treatments. Of the four polyenes, natamycin showed the least increase in TBA reactivity. 

Disproportionation. The hydrogenation of MNoP into TBHA is so fast that the disproportionation of TBHA may be approximated by 2 TBHA -> TBHA + TBA instead of 2 TBHA -> MNoP + TBA. This reaction decreases the TBHA concentration and increase the TBA formation. Depending on the adsorption coefficient value for each organic compound, this process may free a part of the metallic surface area, and therefore favor the MNP conversion. However, this hypothesis can not explain a slowing down of the reaction due to the addition of another active carbon. 

The TBA formation constants are not as accurately determined as the Na constants. The experimental data are though perfectly explained and the reason for the rather high 3a values (see Table 2) is probably due to the more restricted TBA ... 

The binary aqueous systems phase diagrams in the range of the crystallization of TBA carboxylate and isocarboxylate polyhydrates are given in Figures 1 and 2 respectively, and some properties of the hydrates are shown in Table I. Two hydrates with stable crystallization branches form in the TBA acetate - water system. One stable and several metastable hydrates have been discovered in each of the rest of the systems (from 1 (TBA formate) to 8 (TBA o-butyrate)). 

In general, the formation of an ion pair TBA+CgHsO occurs by the reaction between one TBAB molecule and one C HsONa molecule in the water phase. Thus, the ratio of the CgHsONa concentration to the TBAB concentration should be unity if the reaction has occurred in the water phase. The behavior above 50 mM can be simply explained by the reaction in the water phase between one TBAB molecule and one CgHsONa molecule. However, the behavior below 50 mM cannot be explained by this... 

A model calculation showed that the HiPOx system may have been fully successful in limiting bromate formation under the chosen oxidant doses if the influent bromide concentration was 0.56 mg/L or less. Since a bromide concentration of 0.56 mg/L is still extremely high for a drinking water source, the HiPOx system appears to hold promise for destroying MTBE and its oxidative by-product TBA while controlling bromate formation, even in waters that have high bromide concentrations.101... 

Most of the structural and biochemical work related to KDO is based on the estimation of the compound or its derivatives by the periodate-thiobarbituric acid (TBA) assay in its various modifications. Indeed, KDO (see Fig. 3) was discovered9 through the formation of a characteristic, purple, TBA chromophore (Xmax 549 nm) from its 8-phosphate (2), which is the product of the condensation of D-arabinose 5-phosphate with enolpyruvate phosphate, catalyzed by 3-deoxy-8-0-phosphonooctulosonate synthetase (EC 4.1.2.16) (see Scheme 1 and Section V,2). 

The TBA assay for 3-deoxyglyc-2-ulosonic acids, used by Weissbach and Hurwitz11 to determine 3-deoxy-D-arabino-2-heptulosonic acid, was subsequently applied by Warren13 and by Aminoff14 to the analysis ofN-acetylneuraminic acid (NeuAc, 5 see Fig. 4). The formation of the 3-formylpyruvate-derived chromophore 4 in the periodate... 

In the dimerization of isobutene, tertiary-butyl alcohol (TBA, 2-methyl-2-propanol) has a strong role in modifying the selectivity of the reaction to Cg hydrocarbons and limits further oligomerization to C12 and Ci6 hydrocarbons [34]. Also, in the etherification of glycerol with isobutene the addition of TBA has a clear effect on the selectivity and on hydrocarbon distribution. The selectivity to ethers increased and the fraction of the Cu and Ci6 hydrocarbons decreased while the concentration of TBA was increased from 0 to 2.6 mol.%. As a conclusion, the formation of C12 and C16 hydrocarbons can be prevented in two ways either TBA should be added to the reaction mixture or the reaction should be carried out at high temperatures [8]. 

Aqueous NaOH (50%, 80 ml) is added to a vigorously stirred solution of the glycoside (5 mmol) and TBA-Br (0.16 g, 0.5 mmol) in CH2Br2 (50 g) at 60-65°C. The reaction is monitored by TLC and, on completion, the organic phase is separated, washed well with H20, dried (MgS04), and evaporated to yield the acetals (replacement of CH2Br2 by CH2Cl2 and reaction temperatures of 25-35°C allows the formation of intermolecular acetals, but not intramolecular acetals). 

Method B The chloroalkane or a,w-dichloroalkane (0.1 mol) and HC02Na (13.6 g, 0.2 mol for the chloroalkane, 27.2 g, 0.4 mol for the a,co-dichloroalkane) are stirred with TBA-Br (1.61 g, 5 mmol) until the reaction is complete (Table 3.16). H20 (10 ml) is added to the cooled mixture. The organic phase is separated, dried (MgS04), and fractionally distilled to yield the formate ester. When aqueous NaOH (50%, 4.5 ml) is added dropwise over 30 min to the vigorously stirred reaction mixture, the alcohol (diol) is formed, which can be isolated by extraction from the reaction mixture with butanone (2 x 20 ml) and fractional distillation. 

The concentration of ozone taken up by the media containing linolenic acid is plotted against time after addition in Figure 8. The rate of ozone breakdown is constant (ozone uptake linear with time) for the first two min until about 0.12 ml ozone are absorbed and then the rate decreases sharply, reaching a steady-state rate of ozone uptake between 10-12 min. This first break in the curve corresponds to an ozone uptake of 0.12 ml + (24 moles/liter) = 0.005 millimoles (or 10 M). This is equivalent to 1 mole of linolenic acid added per mole ozone absorbed. Thiobarbituric acid reactant production is also plotted on the same axis. This compound (TBA reactant) probably arises by formation of a three-carbon fragment (malondialdehyde) from the ozone-induced oxidation of linolenic acid (23). The rate of TBA reactant formation is also linear for the first 2 min at which point the curve undergoes a less pronounced break. Malondialdehyde formation ceases immediately when the ozone is shut off (Scrub 1 on). An oxygen control sample produced no malondialdehyde. 

The products obtained from TBAOH syntheses are often contaminated with small amounts of H3. The addition of TMAOH in the ratio TBA/TMA = 20 appears to eliminate the formation of H3. 

Impurities in the crude tBA feed, most notably water, methanol, acetone, and heavies , do not appear to significantly inhibit the dehydration process (eq 1), although the presence of methanol clearly leads to the formation of additional MTBE (either through etherification of the tBA feedstock, or the isobutylene coproduct). 

The kinetics of the different condensation steps till (7) (and equivalent structures in the TBA system) are similar for TPA and TBA. This is illustrated using GPC data in Fig.2. The GP chromatograms of extracts after 5, 10, 15 and 45 minutes of hydrolysis illustrate the consecutive formation of species identified as dimers of tetracyclic undecamer (4) and (4 ), precursor (5), dimers of precursors (6) and trimer of precursors (7). The assignment is based on the retention volumes and previous identification with 29Si liquid NMR for the TPA system [2]. The GPC traces show that the transformation of species of type (4), (4 ) and (5) into (6) and (7) is slower with TBA than with TPA. This coupling of precursors seems to be hindered by the long butyl chains of occluded TBA. 

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