Protonated ethyl alcohol

Like water, many organic compounds that contain oxygen can act as bases and accept protons ethyl alcohol and ethyl ether, for example, form the oxonium ions I and II. For convenience, we shall often refer to a structure like I as a protonated alcohol and a structure like II as a protonated ether. 

Protonated alcohols and protonated carboxylic acids are very strong acids. For example, protonated methyl alcohol has a p Ta of —2.5, protonated ethyl alcohol has a p Ta of —2.4, and protonated acetic acid has a p Ta of—6.1. 

The best examples of El eliminations are those carried out m the absence of added base In the example cited m Eigure 5 12 the base that abstracts the proton from the car bocation intermediate is a very weak one it is a molecule of the solvent ethyl alcohol At even modest concentrations of strong base elimination by the E2 mechanism is much faster than El elimination... 

HC1 in ethyl alcohol causes a marked drop in the electrical conductivity, which is ascribed to the partial suppression of proton jumps resulting from the capture of protons from the (C2H5OH2)+ ions, thus ... 

Since a small trace of water suffices to produce a large effect, the equilibrium of (43) evidently lies far in favor of the right-hand side (see also Sec. 115), indicating that a water molecule dissolved in ethyl alcohol provides a vacant level for an additional proton that lies lower than the level occupied by the protons in the OH2 group of the (C2H3OH2)+ ion. A proton captured in this lower level of (HaO)+ will have to wait until it receives the necessary energy before it can move back to an alcohol molecule. In the meantime the (H30)+ ion can merely contribute to the electrical conductivity by drifting slowly in the field only when the proton has returned to an alcohol molecule can the rapid proton jumps be resumed. 

Figure 5.21 (a) The methylene protons of ethyl alcohol appear as a quartet with... 

Wender and coworkers conclude that cobalt-catalyzed benzyl alcohol homologation involves the intermediate formation of car-bonium ions (8). However, since the methyl cation (CH3+) is unstable and difficult to form (9), it is more likely that methanol homologation to ethanol proceeds via nucleophilic attack on a protonated methyl alcohol molecule. Protonated dimethyl ether and methyl acetate forms have been invoked also by Braca (10), along with the subsequent formation of methyl-ruthenium moieties, to describe ruthenium catalyzed homologation to ethyl acetate. 

The principles and techniques of nuclear resonance measurements are fairly well known and will not be described in detail here. It may be worthwhile, however, to review briefly what we mean by the chemical shift. For this we turn to the now classical example of ethyl alcohol. In this molecule we have three sets of non-equivalent protons. Under moderate resolution three resonance signals are obtained having intensity ratios 1 2 3. The assignment of the signals is therefore readily made as shown in Fig. 1. The separation between these different signals is referred to as the chemical shift. The three separate... 

Briefly this is all that is involved in the actual measurements. We return to our example of ethyl alcohol. The possibility of applying proton resonance measurements for studying hydrogen bonding In mc.ooules such as this became apparent following the observation by... 

These considerations can be formulated by schemes (e)—(g) below (R1 = H or alkyl). Scheme (e), in which the acid (ester) is protonated and alcohol reacts in non-adsorbed state, corresponds to the mechanisms Aac1 or Aac2 proposed for homogeneous esterification and hydrolysis with ion exchanger catalysts, the mechanism (e) was assumed to be operating in the liquid phase esterification of salicyclic acid with methanol [449] and in the transesterification of ethyl acetate with the same alcohol in dioxan as... 

This step yields ethyl alcohol and the protonated form of benzoic acid. 

Protonated form Ethyl alcohol of benzoic acid... 

A formate ester, such as ethyl formate, reacts with an excess of a Grignard reagent to give (after protonation) secondary alcohols with two identical alkyl groups. 

The abnormal conductance of the hydrogen ion in methyl and ethyl alcohols, which is somewhat less than in water, can also be accounted for by a proton transfer analogous to that suggested for water thus, if the hydrogen ion in an alcohol ROH is represented by ROHJ, the process is... 

The adsorption of liquid ethyl alcohol on AljOj occurs by H bonding (1108), and without doubt other proton donors are similarly affected. Some part of adsorption from binary solutions (e.g. ethyl alcohol and benzene) is explained by the three-step process alcohol H bonds to the surface, chemisorbs, and then the second component (and more alcohol) physically adsorb on this layer. (See Section 11.2.1 for a discussion of the similar action of water on silicic acid.) Such hydroxyl-covered surfaces are industrially important in cracking and other catalytic processes (2172, 956), and in drying. Plank and Drake (1646) discuss the influence of H bonds in the formation of such materials. 

FIGURE 15.2 The mechanism of acid-catalyzed formation of diethyl ether from ethyl alcohol. As an alternative in the third step, the Bronsted base that abstracts the proton could be a molecule of the starting alcohol. 

The reactions were carried out in isopropyl alcohol. This compound was selected as solvent because the natural lifetime of the aromatic radical anion with respect to protonation (1, 3) is longer than in methyl alcohol or ethyl alcohol. The isopropyl alcohol was obtained from Mathe-son, Coleman, and Bell and was freshly distilled over sodium metal through a glass-packed column for each set of runs. Anthracene from Matheson, Coleman and Bell, pyrene from Aldrich Chemical Co., m-terphenyl and p-terphenyl from City Chemical Corp. were purified as described (2). 9,10-Dimethylanthracene obtained from K and K Laboratories, Plainview, N. Y., was recrystallized from isopropyl alcohol solution. 

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