Acidity in gas phase

In recent years Pagani and coworkers have made detailed studies of the problem. In the space available we can only outline their work and interested readers should consult the very detailed papers. The authors have developed special scales of substituent constants for dealing with contiguous functionalities 193. These new substituent constants are a (which seems to be related fairly closely to the ordinary a ), aIB (which bears some relationship to o/, but not that close), and (Tr-, a special delocalization parameter. It is claimed194 that these scales are appropriate for describing interactions between contiguous functionalities, as opposed to literature values which account for remote interactions . Various C—H acidities in gas phase and in solution were successfully correlated by means of multiple regressions on am and chemical shifts for the central carbon in the carbanions. 

It is known that the n-ethanoic acid in gas phase or in non polar media (19), to 276.5 nm for acetone (20). Thus the donor effect of the methyl group, larger than that of the hydroxyl group, is able to induce a red shift of 66.5 nm on the CO group. 

Similar to other bis(perfluoraIkylsulfonyl)imides, known to be very strong protic acids (currently (C4F9S02)2NH holds the record as the strongest acid in gas phase ), cychc imides form stable salts with variety of counter cations, such as ammonium, potassium, sodium, lithium, etc. Lithium salts of 74-76 were patented as conductive salts for nonaqueous electrolytes of hthium batteries. The DesMarteau group reported synthesis and isolation of stable benzenediazonium salt containing anion of imide 75 and unusual reactions of this material. ... 

From Table VII.5, one can see that resonance is the dominant effect responsible for the greater acidity exhibited by the carboxylic acids in gas phase, when compared to the acidity of the corresponding alcohols, in agreement with the traditional interpretation. More recently, Burk and Schleyer [54] showed that the application of the Siggel and Thomas approach can lead to contradictory conclusions about whether the difference in acidity between methanol and formic acid is determined by the... 

Koppel et al. [346] compared the acidities of 73 NH acids in gas-phase dimethyl sulfoxide, and water. Overall they found that the acidities in the different phases were strongly correlated, and that substituent effects on the acidities of these acids were significantly reduced in both solvent phases. 

LA. Koppel, J. Koppel, V. Pihl, I. Leito, M. Mishima, V.M. Vlasov, L.M. Yagupolskii, and R.W. TafL Comparison of Br0nsted acidities of neutral CH acids in gas phase and dimethyl sulfoxide, J. Chem. Soc. Perkin Trans. 2(2000),pp. 1125-1133. 

Rogers D, Hirst J (2003) Ab initio study of aromatic side chains of amino acids in gas phase and solution. J. Phys. Chem. A 107... 

Paper-contaminated plastics waste collected from the municipal solid waste stream is a potentially inexpensive source of cellulose for bulk composite applications. However, the processing of such waste stream is very difficult because of a high melt viscosity and agglomaration of the cellulose phase. A method for the hydrolytic pretreatment with acid in gas phase of such waste has been recently developed in our laboratories (11). 

Hydrolysis of paper-contaminated palstic waste was carried out using formic acid in gas phase temperature of 180°C for 1 hour. 

An important feature of the cellulose-polymer composites is the degree of dispersion of the fibers in the matrix and the overall homogeneity of the composite structure. Prehydrolytic treatment caused a highly significant improvement in this respect. This has to do primarily with the reduction of particle size of cellulose during hydrolysis. Figure 5 illustrates that the average size of the cellulose content is considerably reduced by 2 hours of hydrolytic treatment with formic acid in gas phase. Processability, measured by melt viscosity, is dramatically improved by hydrolysis. 

Figure 1. Influence of the hydrolysis temperature (melt temperatme in the ractor) on the mechanical properties of plastic waste containing 30% paper. Sample B, formic acid in gas phase, treatment time 3 hours. Values at room temperature (RT) refer to the unhydrohzed sample.

Figure 2. The mechanical properties of untreated and treated (formic acid in gas phase, 200°C, 3 h) plastic waste, sample D, containing 30% paper. Sample D without paper modulus - 1.1 GPa, strength - 17 MPa, elongation at break - exceeding 250%, no break indication at impact testing.

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