What Are the Characteristic Reactions of Alcohols

In this section, we study the acidity and basicity of alcohols, their dehydration to alkenes, their conversion to haloalkanes, and their oxidation to aldehydes, ketones, or carboxylic acids. 

Alcohols have about the same pJ values as water (15.7), which means that aqueous solutions of alcohols have about the same pH as that of pure water. The p of methanol, for example, is 15.5  

In the presence of strong acids, the oxygen atom of an alcohol is a weak base and reacts with an acid by proton transfer to form an oxonium ion  

alcohols can function as both weak acids and weak bases. 

Like water, alcohols react with Li, Na, K, Mg, and other active metals to liberate hydrogen and to form metal alkoxides. In the following oxidation-reduction reaction, Na is oxidized to Na and is reduced to H2  

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The first experiments carried out by Blackmond and Brown employing this technique are shown in Fig. 6 [73]. They demonstrate autocatalytic behavior as expected, and much can be learned about the reaction by analysis of the heat output from scalemic, racemic and enantiopure alcohols in separate experiments. The characteristic shapes permit testing against numerical integration of various model mechanisms. There is an excellent fit assuming what is probably the simplest solution. If the true catalyst is dimeric, and there is no selectivity between the binding constants of homochiral and heterochi-ral forms, yet the heterochiral form is unreactive, a positive non-linear effect ensues. In this case, selectivity is a purely kinetic phenomenon the positive non-linear effect arises because the statistical distribution between homo-and heterochiral forms causes the excess of (S,S)-dimer over (R,R)-dimer to exceed the formal ee. 

A simple criterion, which has the same nature as Ath of the catalyst, was used to represent the electron donor power during reaction the absolute value of the potential ionization difference. A/ = /r — /p, weighed by the ratio p/ r of carbon in product and reactant molecules respectively. The linear correlations obtained between A/ and Ath show that their slope is related to the electron donor power of the reactant, positive when C-C (alkanes, alkyl-aromatics) or C-H (alcohols) bonds are to be transformed, and negative when C=C bonds are concerned. The intercept depends on the extent of oxidation, and its absolute value increases from mild to total oxidation, respectively. A main difficulty is the actual state of cations at the steady state, but each time accurate experiments allow determining the mean valence state, the calculated Ath fits well the correlations. These lines may be used as a predictive trend, and allow, for example, to precise that more basic catalysts are needed for alkane ODH than for its mild oxidation to oxygenated compound. As a variety of solids have been catalytically experienced in literature, it would be worthwhile to consider far more examples than what is proposed here to refine the relationships observed. Finally, theoretical considerations are proposed to tentatively account for these linear relationships. Optical basicity would be closely related to the free enthalpy, and, as an intensive thermodynamic parameter, it is normal that it could be related to several characteristic properties, including now catalytic properties. 

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