Alcohol toward

Increasing reactivity of alcohols toward hydrogen halides... 

Extensive research has established that axial cyclohexanols are more reactive than equatorial alcohols toward chromic acid oxidation. The basis for this effect can be seen... 

Pyridine is more nucleophilic than an alcohol toward the carbonyl center of an acyl chloride. The product that results, an acylpyridinium ion, is, in turn, more reactive toward an alcohol than the original acyl chloride. The conditions required for nucleophilic catalysis therefore exist, and acylation of the alcohol by acyl chloride is faster in the presence of pyridine than in its absence. Among the evidence that supports this mechanism is spectroscopic observation of the acetylpyridinium ion. An even more effective catalyst is 4-dimeftiyIaminopyridine (DMAP), which functions in the same wsy but is more reactive because of the electron-donating dimethylamino substituent. ... 

Pal, B., Sen, P.K. and Sen Gupta, K.K. (2001) Reactivity of alkanols and aryl alcohols towards tetrachloroaurate(lll) in sodium acetate-acetic acid buffer medium. Journal of Physical Organic Chemistry, 14, 284. 

At the beginning of this decade, Zewail and coworkers reported a fundamental work of solvation effect on a proton transfer reaction [195]. a-naphthol and n-ammonia molecules were studied in real-time for the reaction dynamics on the number of solvent molecules involved in the proton transfer reaction from alcohol towards the ammonia base. Nanosecond dynamics was observed for n=l and 2, while no evidence for proton transfer was found. For n=3 and 4, proton transfer reaction was measured at pisosecond time scale. The nanosecond dynamics appears to be related to the global cluster behavior. The idea of a critical solvation number required to onset proton transfer... 

Because of the very acidic solutions involved, these methods are limited to acid-stable molecules. Milder reagents are necessary for most functionally substituted alcohols. A very general and important method for activating alcohols toward nucleophilic substitution is by converting them to alkoxyphosphonium ions.14 The alkoxyphosphonium ions are very reactive toward nucleophilic attack, with the driving force for substitution being formation of the strong phosphoryl bond. 

To estimate the relative reactivity of allylic, benzylic, and nonconjugative aliphatic alcohols toward the Ar3BiCl2/DBU system, intermolecular competitive oxidations were examined. As summarized in Scheme 20, cinnamyl and benzylic alcohols were preferentially oxidized in the presence of ethyl alcohol. The chemos-electivities observed for the Ar3BiCl2/DBU oxidant (Ar = o-tolyl) are considerably higher than those achieved by Dess-Martin periodinane [83, 84]. 

A general and important method for activating alcohols toward nucleophilic substitution is by converting them into alkoxyphosphonium ions ... 

The behaviour of unsaturated alcohols towards this oxidant has also received attention. An initially formed alkenyloxy radical can add to the double bond and the resulting carbon... 

The oxidation of substituted /3-benzoylpropionic acids by PFC follows the Hammett relation with a negative reaction constant. A possible mechanism for the oxidation has been discussed.5 The oxidation of maleic, fumaric, crotonic, and cinnamic acids by PCC is of first order with respect to PCC and the acid. The oxidation rate in 19 organic solvents has been analysed by Kamlet s and Swain s multiparametric equations. A mechanism involving a three-centre transition state has been postulated.6 The relative reactivity of bishomoallylic tertiary alcohols toward PCC, to yield substituted THF products via the tethered chromate ester, is dependent only on the number of alkyl groups. This observation suggests a symmetrical transition state in this intramolecular Cr(VI)-alkene reaction.7 Mechanisms have been proposed for the oxidation of 2-nitrobenzaldehyde with PBC8 and of crotonaldehyde with tetraethylammonium chlorochromate.9... 

The reactivity of alcohols toward sodium and potassium decreases in the order methyl > 1° > 2° > 3°. Sodium reacts quickly with primary alcohols and some secondary alcohols. Potassium is more reactive than sodium and is commonly used with tertiary alcohols and some secondary alcohols. 

The addition of protic reagents such as an alcohol toward the double bond of unsaturated heavier group 14 elements is one of the most important reactions. The reaction usually occurs cleanly and in a high yield, and is taken as evidence for the existence of a doubly bonded compound. 

The reaction of NO3 with unsaturated ethers proceeds by addition to the >C=C< double bond. Both steric and inductive effects are known to influence the reactivity of NO3 with unsaturated alcohols, e.g. 2-methyl-3-butene-2-ol is slightly less reactive than 1-butene. Unsaturated ethers are more reactive than unsaturated alcohols towards NO3. Comparison of the measured rate constants shows that, similar to the reaction with O3, the presence of the carbonyl group decreases the reactivity of NO3 toward the >C=C< double bond. The reaction of NO3 with unsaturated oxygenates proceeds by addition to either one of the carbon atoms of >C=C< double bond, preferentially to the most substituted radical. In the presence of NOx, the reaction may ultimately lead to organic nitrates among the first generation products. 

A mixture of weak, impure alcohol and fusel oil ( hot feints ) collects in the bottom of the rectifier. This is returned to the analyzer to recover the alcohol. Towards the end of the distillation of a batch, however, instead of completing the purification of all the alcohol, it is found more economical to raise the temperature of the apparatus and distill off the whole residue of impure spirit. This is condensed and collected as feints in a separate receiver. Here the fusel oil which has accumulated throughout the process separates, to a large extent, from the weak spirit and is skimmed off. The remaining feints are redistilled with the wash of a succeeding operation to recover their ethyl alcohol. 

No simple correlation between the electronegativity of zeolites and the conversion of methanol is observed (Fig.3). It is caused by two competitive processes which occurs during the reaction between ROH and H2S i.e. transformation of alcohols towards hydrocarbons (increasing with the increase of the zeolite electronegativity) and hydrosulphurization of alcohols towards thiols (decreasing with the increase of the electronegativity). ... 

Many of the reagents that are used to activate alcohols toward nucleophilic substitution (e.g., SOCI2, PCI3) cannot be used to activate ethers. When an alcohol reacts with an activating agent such as a sulfonyl chloride, a proton dissociates from the intermediate in the second step of the reaction and a stable sulfonate ester results. 

Alkoxy-l, 3-benzodithioles (1). Carbon disulfide undergoes 1,3-dipolar cycloaddition to benzyne [generated from benzenediazonium-2-carboxylate (1,46)] to give 1,3-benzodithiole-2-carbene (a). This carbene reacts with alcohols to form (1) in 35-50% yields. The reaction can be carried out in one-step from anthranHic acid, since carbon disulfide is more reactive than alcohols toward benzyne. ... 

As the result of the fermentation there is obtained a mixture which contains water, alcohol, fusel oil, acids, yeast cells, and other substances. The alcohol, which is present to the extent of from 10 to 13 per cent, is separated by distillation. Very efficient rectifying apparatus is used in distilling the dilute solution of alcohol. After two distillations alcohol containing but 4 per cent of water is obtained. A mixture of alcohol and water which contains 96 per cent of alcohol by weight cannot be separated into its constituents by distillation, as a mixture of this composition has a constant boiling point below that of pure alcohol. Toward the end of the distillation there is obtained what is called fusel oil, which consists of two isomeric amyl alcohols, CsHnOH, together with small quantities of other alcohols. 

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