Acidity alcohols and phenols

Since the imidazolide method proceeds almost quantitatively, it has been used for the synthesis of isotopically labeled esters (see also Section 3.2), and it is always useful for the esterification of sensitive carboxylic acids, alcohols, and phenols under mild conditions. This advantage has been utilized in biochemistry for the study of transacylating enzymes. A number of enzymatic transacylations (e.g., those catalyzed by oc-chymo-trypsin) have been shown to proceed in two steps an acyl group is first transferred from the substrate to the enzyme to form an acyl enzyme, which is then deacylated in a second step. In this context it has been shown[21] that oc-chymotrypsin is rapidly and quantitatively acylated by Af-fraw.s-cinnamoylimidazole to give /ra/w-cinnamoyl-a-chymotrypsin, which can be isolated in preparative quantities and retains its enzymatic activity (see also Chapter 6). 

The organic compounds of potassium include many oxycompounds, such as salts of organic acids, alcohols and phenols (alkoxides, phenoxides, etc.). A few potassium-carbon linked compounds have been reported, such as a phenyhsopropyl potassium. C6H5C3H7K, and a carbonyl compound of unknown composition. Kx(f 0)Y. The adduct of ethyl potassium and diethyl-zinc is a true salt, K2[Zn(C2H5)4], potassium tetraethylzincate. 

As weak acids, alcohols and phenols dissociate to a slight extent in dilute aqueous solution by donating a proton to water, generating H3O and an alkoxide ion, RO, or a phenoxide ion, ArO ... 

Figs. 26.4 and 26.5 give the value of xa for solutions of acids, alcohols and phenol in various solvents. In the case of the acids, xa determined from cryoscopic measurements, while for the alcohols and phenol from spectroscopic data. There is a striking difference between the behaviour of the acids compared with the alcohols and phenol. For acids xa rises rapidly to a saturation value of about two. On the other hand, for alcohols and phenol, Xa continues to rise steadily and reaches values much greater than two, and furthermore the curves are strongly dependent on both... 

Evdakov, V.P, Beketov, V.P, and Svergun. VL, Reaction of amidophosphites and acetylphosphites with acetic acid, alcohols, and phenol, Zh. Obshch. Khim., 43, 55, 1973 Chem. Abstr, 78, 123523, 1973. 

Carboxylic acids, alcohols, and phenols are neutral in their acidic forms (HB) and charged in their basic forms (B ). A polar protic solvent will stabilize B and H more than it will stabilize HB, thereby increasing Kg. Therefore, Kg will be larger in water than in a less polar solvent, which means that the Kg value will be lower in water. So the pK values of carboxylic acids, alcohols, and phenols determined in a less polar solvent than water will be higher than those determined in water. 

Elevated temperature reaction pyrolysis in which the analyte is reacted with a chemical reagent. The method is appropriate for those materials that contain hydrolyzable bonding or free reactive groups, e.g., acids, alcohols, and phenols. Usually, the pyrograms more clearly reflect the composition of the parent material. A review of the technique describes applications to nonforensic materials. ... 

Relative pK calculations can be highly accurate, within a few tenths of a kcal/mol, as errors in both the gas-phase and solution-phase values tend to cancel [7]. Numerous highly accurate relative pK values have been reported in the literature. For instance, a comprehensive study on a large set of carboxylic acids, alcohols, phenols, and amines using B3LYP for the gas-phase and PCM for the solution-phase calculations spanned over 16 orders of experimental pK values, and resulted in standard deviations of 0.37, 0.40, and 0.52 pK units for carboxylic acids, alcohols and phenols, and amines, respectively [150]. Nino and co-workers report highly accurate relative pK calculations for aminopyridines [120], while Brown and Mora-Diez published moderate relative results for protonated benz imidazoles [38]. A computational study of the acid dissociation of esters... 

For efficient action of Y as cocatalysts, it is necessary that in reactions with alkyl halides they behave as bases abstracting proton not as nucleophiles entering undesired nucleophilic substitution. From a variety of possible Y-H, only OH acids—alcohols and phenols, and to smaller extent some NH acids—are shown to be proper cocatalysts. In a model studies of base-induced PTC j8-elimination of HBr from cyclohexyl bromide, it was shown that benzyl and benzhydryl alcohols, 2,2,2-trifluoroethanol, trifluoromethylphenyl carbinol, and mesitol are particularly efficient cocatalysts (71) as shown in equation 159. 

Aluminum alloys are resistant to a wide variety of organic compounds including most aldehydes, esters, ethers, hydrocarbons, ketones, mercap-tans, other sulfur-containing compounds, and nitro compounds. They are also resistant to most organic acids, alcohols, and phenols, except when these compounds are nearly dry and near their boiling points. Carbon tetrachloride also exhibits this behavior. 

Examples of alkylation, dealkylation, homologation, isomerization, transposition, etc. are found in Sections 1, 17, 33, and so forth, which lie close to a diagonal of the index. These sections correspond to the preparation of acetylenes from acetylenes, carboxylic acids from carboxylic acids, alcohols and phenols from alcohols and phenols, etc. 

C2H4N2O3, NH2CONHCOOH. Unknown in the free state as it breaks down immediately to urea and COi- The NH4, Ba, Ca, K and Na salts are known and are prepared by treating ethyl allophanate with the appropriate hydroxide. The esters with alcohols and phenols are crystalline solids, sparingly soluble in water and alcohol. They are formed by passing cyanic acid into alcohols or a solution of an alcohol or phenol in benzene. The amide of allophanic acid is biuret. Alcohols are sometimes isolated and identified by means of their allophanates. 

Although these nitrations proceed smoothly, attempted nitration of an unidentified substance should always be carried out with extreme care, e.g., by working in a fume-cupboard and pointing the boiling-tube away from the operator. Many organic substances e.g., alcohols and phenols) react with great violence with a mixture of nitric and sulphuric acids. 

Sulfonic acids are prone to reduction with iodine [7553-56-2] in the presence of triphenylphosphine [603-35-0] to produce the corresponding iodides. This type of reduction is also facile with alkyl sulfonates (16). Aromatic sulfonic acids may also be reduced electrochemicaHy to give the parent arene. However, sulfonic acids, when reduced with iodine and phosphoms [7723-14-0] produce thiols (qv). Amination of sulfonates has also been reported, in which the carbon—sulfur bond is cleaved (17). Ortho-Hthiation of sulfonic acid lithium salts has proven to be a useful technique for organic syntheses, but has Httie commercial importance. Optically active sulfonates have been used in asymmetric syntheses to selectively O-alkylate alcohols and phenols, typically on a laboratory scale. Aromatic sulfonates are cleaved, ie, desulfonated, by uv radiation to give the parent aromatic compound and a coupling product of the aromatic compound, as shown, where Ar represents an aryl group (18). 

The triaLkoxy(aryloxy)boranes are typically monomeric, soluble in most organic solvents, and dissolve in water with hydrolysis to form boric acid and the corresponding alcohol and phenol. Although the rate of hydrolysis is usually very fast, it is dependent on the bulk of the alkyl or aryl substituent groups bonded to the boron atom. Secondary and tertiary alkyl esters are generally more stable than the primary alkyl esters. The boron atom in these compounds is in a trigonal coplanar state with bond hybridization. A vacantp orbital exists along the threefold axis perpendicular to the BO plane. 

In an analogous manner, DCPD reacts with alcohols and phenols to form ether derivatives, and with halogen acids, thiocyanic acid, and various carboxyhc acids to form esters. These esters are used as perfume components (67). Dicyclopentadiene alcohol and a number of the ethers, esters, and glycol adducts have been claimed as coal and ore flotation aids (68). 

The reaction of alcohols and acid chlorides in the presence of magnesium has been described (68). With primary and secondary alcohols the reaction is very smooth, and affords high and sometimes quantitative yields. Difficulty esteritiable hydroxy compounds such as tertiary alcohols and phenols can be esteritied by this method. The reaction carried out in ether or benzene is usually very vigorous with evolution of hydrogen. 

Isopropenyloxytrimethylsilane. In the presence of an acid catalyst the reagent silylates alcohols and phenols. It also silylates carboxylic acids without added catalyst. 

The chemical resistance of the linear polymers is also very good. Resistant to most acids, aqueous bases, hydrocarbons, most halogenated hydrocarbons, alcohols and phenols, they are attacked by concentrated sulphuric acid, formic acid, some amines, benzaldehyde, nitromethane and a few other reagents. They will dissolve in 1-chloronaphthalene at elevated temperatures but in general have excellent solvent resistance. The polymer is cross-linked by air oxidation at elevated temperatures. 

Carboxylic acids react with trifluoroacetic anhydride to give mixed anhydrides that are especially useful for the acylation of hindered alcohols and phenols ... 

Bis(2,2,2-trifluoroethyl)]phosphite can be used to prepaie esters of phos phorous acid by a transestenfication reaction with alcohols and phenols [750] (equation 78)... 

Another similarity with water is that alcohols and phenols are both weakly basic and weaJkly acidic. As weak bases, they are reversibly protonated by strong acids to yield oxonium ions, TOFty. ... 

Table 17.1 Acidity Constants of Some Alcohols and Phenols...

Although much weaker than mineral acids, carboxylic acids are nevertheless much stronger acids than alcohols and phenols. The Ka of ethanol, for example, is approximately 10 l6, making ethanol a weaker acid than acetic acid... 

Reaction with alcohols is general for diazo compounds, but it is most often performed with diazomethane to produce methyl ethers or with diazo ketones to produce ot-keto ethers, since these kinds of diazo compounds are most readily available. With diazomethane the method is expensive and requires great caution. It is used chiefly to methylate alcohols and phenols that are expensive or available in small amounts, since the conditions are mild and high yields are obtained. Hydroxy compounds react better as their acidity increases ordinary alcohols do not react at... 

The addition of alcohols and phenols to double bonds is catalyzed by acids or bases. When the reactions are acid catalyzed, the mechanism is electrophilic, with H as the attacking species. The resulting carbocation combines with a molecule of alcohol ... 

Both alcohols and phenols add to ketenes to give carboxylic esters (R2C=C= O+ROH —> R2CHC02R). This has been done intramolecularly (with the ketene end of the molecule generated and used in situ) to form medium- and large-ring lactones. In the presence of a strong acid, ketene reacts with aldehydes or ketones (in their enol forms) to give enol acetates. 

Further examples of the reaction RCO2H + R OH -> RCO2R are included in Section 108 (Esters from Alcohols and Phenols) and in Section 30A (Protection of Carboxylic Acids). 

Further examples of the reaction ROH -> RC02R are included in Section 107 (Esters from Acid Derivatives) and in Section 45 A (Protection of Alcohols and Phenols). 

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