Hydration and Related Reactions

Calculations support a cooperative mechanism for the hydration of formaldehyde, acetaldehyde, acetone, and cyclohexanone in water. The results are supported by determination of the rate constant for the neutral hydration of acetone, using labelled acetone and water. Conclusions include  

Gas-phase acid-catalysed additions of water and methanol to ethanol and its a-halo derivatives have been investigated by computation both reactions are favoured by increasing the electronegativity of the halogen.  

The energy barrier for the gas-phase addition of ammonia to formaldehyde has been calculated, and a molecular dynamics study of its hydration in aqueous sulphuric acid is reported.  

For hydration of an o -aminotetrahydropyranone, and the hydrate and hydrate anion of a,a,a-trifluoroacetophenone, see under Acetals and Aldols above, respectively. 

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Acid-Catalyzed Hydration and Related Addition Reactions... 

SECTION 6.2. ACID-CATALYZEO HYDRATION AND RELATED ADDITION REACTIONS... 

Fries rearrangement, 18 336, 337 isomerization and transalkylation of alky-laromatics, 18 329 epoxide transformations, 18 351-352 hydration and ammonolysis of ethylene oxide, 18 351, 352 isomerization, 18 351 framework composition, 33 226-228 hydrogenation, dehydrogenation, and related reactions, 18 360-365 dehydrocyclization of s-ethylphenyl using zeolites and carbonyl sulfide, 18 364, 365... 

Hydration and dehydration reactions have proved particularly convenient for studying catalysis by acids and bases over a wide range of structures and catalytic power. The results usually show a good correlation between acidic and basic catalytic constants and k ) and the of the catalyst, according to the usual Bronsted relations kjp = Ga qK /p) , ki, q = Gi, pjqKf, where p and q are statistical corrections. (These statistical corrections have not always been applied consistently, but the discrepancies thus introduced are not serious.) The information so far obtained is summarized in Table 3, and comments on the individual reactions follow. 

Hydration and hydrolysis reactions. We have seen (Chapters 4 and 8) that large charge-to-size ratios for cations result in an increase in hydration energies. Closely related to hydration and, in fact, inseparable from it except in degree is the phenomenon of hydrolysis. In genera], we speak of hydration if no reaction beyond simple coordination of water molecules to the cation occurs ... 

II. PROTON AS AN ELECTROPHILE A. Hydration, Addition of ROH and Related Reactions... 

Carbonyl compounds, reversible hydration of, 4, 1 Carbonyl compounds, simple, enolisation and related reactions of, 18, 1 Carboxylic acids, tetrahedral intermediates derived from, spectroscopic detection and investigation of their properties, 21, 37... 

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