Hydrocarbon acidity

Using the relationship from the preceding section that the effective electronega tivity of carbon m a C—H bond increases with its s character (sp < sp < sp) the order of hydrocarbon acidity behaves much like the preceding methane ammonia water hydrogen fluonde series... 

In general, the reactions of the perfluoro acids are similar to those of the hydrocarbon acids. Salts are formed with the ease expected of strong acids. The metal salts are all water soluble and much more soluble in organic solvents than the salts of the corresponding hydrocarbon acids. Esterification takes place readily with primary and secondary alcohols. Acid anhydrides can be prepared by distillation of the acids from phosphoms pentoxide. The amides are readily prepared by the ammonolysis of the acid haUdes, anhydrides, or esters and can be dehydrated to the corresponding nitriles (31). 

Petroleum Oils. When satisfactorily stable kerosene—soap—water emulsions were produced in 1874, dormant (winter) oil sprays became widely used to control scale insects and mites (1). The first commercial emulsion or miscible oil was marketed in 1904 and by 1930 highly refined neutral or white oils, free from unsaturated hydrocarbons, acids, and highly volatile elements, were found to be safe when appHed to plant foHage, thus gready enlarging the area of usefulness of oil sprays (see Petroleum). 

It has been found that there is often a correlation between the rate of deprotonation (kinetic acidity) and the thermodynamic stability of the carbanion (thermodynamic acidity). Because of this relationship, kinetic measurements can be used to construct orders of hydrocarbon acidities. These kinetic measurements have the advantage of not requiring the presence of a measurable concentration of the carbanion at any time instead, the relative ease of carbanion formation is judged from the rate at which exchange occurs. This method is therefore applicable to very weak acids, for which no suitable base will generate a measurable carbanion concentration. 

For synthetic purposes, carbanions are usually generated in ether solvents, often THF or DME. There are relatively few quantitative data available on hydrocarbon acidity in such solvents. Table 7.2 contains a few entries for Cs salts. The numerical values are scaled with reference to the pAT of 9-phenylfluorene. ... 

Methanetrisulfonyl fluoride, HC(S02p)3, strong hydrocarbonic acid... 

A different approach to the problem of hydrocarbon acidity, and hence carbanion stability, is that of Shatenshtein and Shapiro, who treated hydrocarbons with deuterated potassium amide and measured the rates of hydrogen exchange. The experiments did not measure thermodynamic acidity, since rates were measured, not positions of equilibria. They measured kinetic acidity, that is, which compounds... 

Because the pore dimensions in narrow pore zeolites such as ZSM-22 are of molecular order, hydrocarbon conversion on such zeolites is affected by the geometry of the pores and the hydrocarbons. Acid sites can be situated at different locations in the zeolite framework, each with their specific shape-selective effects. On ZSM-22 bridge, pore mouth and micropore acid sites occur (see Fig. 2). The shape-selective effects observed on ZSM-22 are mainly caused by conversion at the pore mouth sites. These effects are accounted for in the hydrocracking kinetics in the physisorption, protonation and transition state formation [12]. 

Table Some stable all-hydrocarbon anions derived from hydrocarbon acids with pA a values 7.

Gas Gas-vapour Gas-liquid Gas-solid Gas-liquid-solid Mist Fume SO2 NOxI HCI CO hydrocarbons Acid mist carryover chromic acid oil mists tar fog Metal oxides, cement dust Paint spray... 

Table IX. Fluorinated Hydrocarbons, Acids, and Acid Derivatives Patented as General...

The result obtained by GC-MS, with the same SPME conditions, from the black thick balm of a crocodile mummy (sample 1400, Musee Guimet, Lyon, France) is presented in Figure 10.11. The composition of the extract is close to that of sample 1998 but phenolic compounds were not detected. The GC-MS chromatogram obtained with the same substance after acid methanolysis and silylation is presented in Figure 10.12. Except for the sesquiterpenoids eluted between 10 min and 22 min, the observed compounds originate from a beeswax. The biomarkers of this substance are hexadecanoic acids hydroxylated in position 14 or 15 and long chain hydrocarbons, acids and alcohols eluted between 50 min and 90 min. Diterpenoid or triterpenoid resin components are not observed. 

Separation procedures for purely organic species do not possess the same degree of selectivity as systems involving metals because of a general lack of suitable complexing and masking reactions. Nevertheless, classes of compounds such as hydrocarbons, acids, fats, waxes, etc., can often be isolated prior to analysis by other techniques. 

A similar strategy was used to develop the PFGC-MES equation of state parameters for describing the behavior of methanol hydrocarbon acid gas water systems. Multiple phase binary interaction parameters were used as required. Again, these second phase binary interaction parameters were usually not temperature dependent. 

Validation of the PFGC-MES on methanol-water-hydrocarbon-acid gas systems was practically impossible. Many investigators have reported data for the C5 - Ca paraffin aromatic naphthenic... 

The ability of the SRK equation of state to reliably predict the vapor phase water content of natural and synthetic gas systems has been demonstrated. In addition, the ability of the PFGC-MES equation to describe the phase behavior of hydrocarbon, acid gas, methanol, water systems has been described. Both... 

Studies of the effect of ring strain on hydrocarbon acidity reveal a general increased acidity in the position ortho (a) to strained ring annelation. See Streitwieser, A. Jr. Ziegler, G. R. Mowety, P. C. Lewis, A. Lawler, R. G. J. Am. Chem. Soc. 1968, 90,1357. 

To promote the cross polymerization of olefins the concentration of the more reactive isobutene is kept low by recycling a stream of hydrocarbon-acid emulsion having a low iso-... 

The mixture leaving the reaction zone is in the form of a hydrocarbon-acid emulsion and passes to an acid settler for separation of acid and hydrocarbon phases. This acid settler is usually a separate vessel from the reactor itself, although it is an integral part of one type of system. The hydrocarbon-free acid from the acid settler recirculates to the reactor. The hydrocarbon layer, which consists of alkylate, excess isobutane, and the inert diluents introduced with the feed, receives a caustic treatment and goes to the fractionating section of the plant. Caustic treatment is necessary at this stage of the process to neutralize acidic components, such as sulfur dioxide, which are formed in small quantities by catalyst degeneration. 

As the alkylation catalyst ages, its titratable acidity decreases because it becomes diluted with water from the feed stock and with water and complex hydrocarbon oils produced by side reactions. The catalyst is ordinarily discarded when its titratable acidity drops to 85 to 88%. If the catalyst is used further, the quality of the alkylate deteriorates rapidly, and the hydrocarbon-acid emulsion becomes so stable that separation difficulties are encountered in the acid settler. 

As in sulfuric acid alkylation, the hydrocarbon-acid emulsion passes from the contactor into an acid settler for separation of acid and hydrocarbon phases and the acid layer recirculates to the reactor. Unlike sulfuric acid, however, hydrofluoric acid is appreciably soluble in hydrocarbons, and as much as 1% by weight may be retained in the hydrocarbon layer. The necessity of recovering this acid from the hydrocarbon phase results, in another difference between hydrofluoric and sulfuric acid processing in that a hydrofluoric acid stripper is required. This stripper is ordinarily packed with aluminum rings which serve not only as tower packing but also as a catalyst for the decomposition of organic fluorides into hydrocarbons and free hydrofluoric acid. 

For a monograph on hydrocarbon acidity, see Reutov Beletskaya Butin CH-Acids Pergamon Elmsford. NY. 1978. For a review, see Fischer Rewicki Prog. Org. Chem. 1968, 7, 116-161. 

Different catalysts bring about different types of isomerization of hydrocarbons. Acids are the best known and most important catalysts bringing about isomerization through a carbocationic process. Brpnsted and Lewis acids, acidic solids, and superacids are used in different applications. Base-catalyzed isomerizations of hydrocarbons are less frequent, with mainly alkenes undergoing such transformations. Acetylenes and allenes are also interconverted in base-catalyzed reactions. Metals with dehydrogenating-hydrogenating activity usually supported on oxides are also used to bring about isomerizations. Zeolites with shape-selective characteristics... 

Methanetrisulfonyl fluoride, HC(S02F)3, is a strong hydrocarbonic acid When aqueous solutions are mixed with arenediaznnium chlorides, the corresponding salts are formed. These salts decompose between 80 and 120 °C with a release of nitrogen and formation of aryloxyfluorooxosulfomobis(fluorosulfonyl)meth-... 

Another type of inclusion compd is the channel or canal compound. Here the straight chain compds, such as hydrocarbons, acids,esters , alcohols, aldehydes, ketones, etc are enclosed in the channels formed by compds, such as urea, thiourea, choleic acids, cyclodextrins, etc. As examples of channel compds may be cited, the urea-decone compd, [CO(NH2)2] g.C, 2H26, and various zeolites. (See also Ref 10, pp431 ... 

The other hydrocarbon acids arc not a industrially significant. In many potential markets the lower price of acetic acid keeps them blocked out. Formic acid is used in textile drying and leather treatment. Propionic acid is used in the production of propionates, plasticizers, and herbicides Butyric acid finds a variety of specialty uses in producing plasticizers and esters. 

---