Induced hydrolysis

Acetal formation is reversible (K for MeCHO/EtOH is 0-0125) but the position of equilibrium will be influenced by the relative proportions of R OH and H2O present. Preparative acetal formation is thus normally carried out in excess R OH with an anhydrous acid catalyst. The equilibrium may be shifted over to the right either by azeotropic distillation to remove H2O as it is formed, or by using excess acid catalyst (e.g. passing HCl gas continuously) to convert H2O into the non-nucleophilic H3O . Hydrolysis of an acetal back to the parent carbonyl compound may be effected readily with dilute acid. Acetals are, however, resistant to hydrolysis induced by bases—there is no proton that can be removed from an oxygen atom, cf. the base-induced hydrolysis of hydrates this results in acetals being very useful protecting groups for the C=0 function, which is itself very susceptible to the attack of bases (cf. p. 224). Such protection thus allows base-catalysed elimination of HBr from the acetal (27), followed by ready hydrolysis of the resultant unsatu-... 

Tauber A, Mark G, Schuchmann H-P, von Sonntag C (1999a) Sonolysis of ferf-butyl alcohol in aqueous solution. J Chem Soc Perkin Trans 2 1129-1135 Tauber A, Schuchmann H-P, von Sonntag C (1999b) Sonolysis of aqueous 4-nitrophenylacetate- no evidence for hydrolysis induced by transient supercriticality. Chem Eur J 5 2198-2202 Tauber A, Schuchmann H-P, von Sonntag C (2000) Sonolysis of aqueous 4-nitrophenol at low and high pH. Ultrason Sonochem 7 45-52... 

Yeast showed an accumulation of PolyP3 following PolyP hydrolysis induced by amines and basic amino acids (Greenfeld et al., 1987). The degradation of NMR-observable , probably vacuolar, PolyP to short-chain polymers in the cells of Chemostat-cultivated S. cerevisiae contributed to neutralizing the added alkalinity (Castro et al., 1995, 1999). In contrast, when the vacuolar vphl-1 mutant, lacking NMR-visible PolyP, was subjected to alkalinization, the absence of a vacuolar source of phosphate slowed re-acidification (Castro et al., 1999). Anaerobiosis resulted in the complete hydrolysis of PolyP to P (Castro etal, 1995). 

To improve the notched impact strength and to prevent hydrolysis induced embrittlement of PBT, PBT-styrenic blends have been thoroughly investigated. In comparison with ASA-PC, blends of ASA and PBT generally have to be compa-tibilized in order to yield acceptable mechanical properties. In the case of glass fibre reinforced PBT-ASA blends, an added and important bonus is reduced warpage properties on injection moulding in comparison with reinforced PBT. 

Kaiser, K., and Benner, R. (2005). Hydrolysis-induced racemization of amino acids. Limnology and... 

Amelung, W., and Brodowski, S. (2002). In vitro quantification of hydrolysis-induced racemization of amino acid enantiomers in environmental samples using deuterium labeling and electron-impact ionization mass spectrometry. Anal. Client. 74, 3239-3246. 

Figure 29.30. Translocation Mechanism. In the GTP form, EF-G binds to the EF-Tu-binding site on the 50S subunit. This stimulates GTP hydrolysis, inducing a conformational change in EF-G, and driving the stem of EF-G into the A site on the 308 subunit. To accommodate this domain, the tRNAs and mRNA move through the ribosome by a distance corresponding to one codon.

ATP Binding and Hydrolysis Induce Changes in the Conformation and Binding Affinity of Motor Proteins... 

Agrawal R K, Heagle A B, Penczek P, Grassucci R A and Frank J 1999 EF-G-dependent GTP hydrolysis induces translocation accompanied by large conformational changes in the 70S ribosome Nature Struct. Biol. 6 643-7... 

Asenjo, A. B., Weinberg, Y, and Sosa, H. (2006) Nucleotide binding and hydrolysis induces a disorder-order transition in the kinesin neck-hnker region, Nat. Struct. Mol. Biol. 13, 648-654. 

Imide function hydrolysis inducing polymer chain scissions, comparison with Nation membranes... 

Thompson DG, Osborn JC, Kober EM, Schoonover JR. Effects of hydrolysis-induced molecular weight changes on the phase separation of a polyester polyurethane. Polym Degrad Stab 2006 91(12) 3360-70. 

One would expect aldoses to combine the chemistries of alcohols and aldehydes, and that expectation is correct. In fact, the proximity of these functional groups leads to important intramolecular chemistry, and here is an example. Although reduction of glucose with sodium borohydride followed by hydrolysis induces the expected change (see Problem 22.6), modern spectroscopic methods such as NMR and IR do not reveal the presence of substantial amounts of the aldehyde in the starting carbohydrate (Fig. 22.10). It is important to understand why this is so. The chemistry of the aldose tells us there is an aldehyde and we certainly have been drawing an aldehyde group in our Rscher projections. So why cant we observe the aldehyde spectroscopically ... 

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