Acid strengths determination

Acid strength determines to what extent an acid reacts with water. All acids react extensively with Arrhenius bases. 

The acid strength determination is made by placing approximately 0.2 ml of the... 

Reduced and unreduced copper Y zeolites are prepared from sodium Y zeolites (NaY) and their catalytic activity towards dehydration of tertiary butyl alcohol (t-BuOH) is evaluated in relation to pure NaY and HY zeolites. They are characterised by chemical analysis, XRD, TG/DTA and IR spectroscopy. The catalytic activity followed the order NaY < CuY < HY < Cu(R). The activities of the catalyst could be correlated to the corresponding acid strength determined by temperature progranuned desorption of ammonia. 

The w-cresol transformation was carried out on wide pore zeolites (HFAU, HBEA, HMOR and HOFF). The activity follows the sequence HFAU > HBEA HMOR > HOFF. The order of the acid strength determined by TPD-NH3 was HMOR>HOFF>HBEA>HFAU. On the HBEA. HMOR and HOFF the isomerization was the main reaction due to their pore system structure, that limits the formation of diphenylmethane intermediate of disproportionation, while on HFAU the disproportionation reaction was not impeded at low conversion. The p o selectivity is mainly function of conversion. 

Acid dissociation constant (Ka) A mathematical measure of acid strength, determined from the equilib-... 

Acid strength determination.- Acid centres of both Brbnsted and Lewis types can exist on solid surfaces. The BreSnsted sites are groups able to lose protons, while Lewis centres are surface sites which can accept electron pairs from adsorbing molecules. Acidic properties of the centre are characterized by the value of acid strength. For the Brdnsted acid sites, acid strength is defined by acidity functions as for acid solutions. The most... 

Table 5. Acid strength determination by means of test reactions. ...

The experimental details of the acid strength determination are described in earlier publications. The acid strength of a solid superacid which is very sensitive to moisture can be determined by observing the color change of an indicator whose vapor... 

The combination of oxidi2ing effect, acidic strength, and high solubiHty of salts makes perchloric acid a valuable analytical reagent. It is often employed in studies where the absence of complex ions must be ensured. The value of wet ashing techniques, in which perchloric acid is used to destroy organics prior to elemental analysis for the determination of trace metals in organics, has been well estabHshed (see Trace and residue analysis). 

Mechanistically the rate-determining step is nucleophilic attack involving the hydroxide ion and the more positive siUcon atom in the Si—H bond. This attack has been related to the Lewis acid strength of the corresponding silane, ie, to the abiUty to act as an acceptor for a given attacking base. Similar inductive and steric effects apply for acid hydrolysis of organosilanes (106). 

Applications of neural networks are becoming more diverse in chemistry [31-40]. Some typical applications include predicting chemical reactivity, acid strength in oxides, protein structure determination, quantitative structure property relationship (QSPR), fluid property relationships, classification of molecular spectra, group contribution, spectroscopy analysis, etc. The results reported in these areas are very encouraging and are demonstrative of the wide spectrum of applications and interest in this area. 

Most of the chemistry of PA is determined by its acidic nature. It is a strong acid whose ionization constant of 1.6 x 10"1 (Ref 31) makes it comparable in acid strength to pyrophosphoric acid and trichloroacetic acid. PA readily forms salts with bases and esters with alcohols. The salts are known as Picrates. Many of them are expl and will be described in a separate article in this Vol. The esters are phenol ethers, eg, Trinitro-anisolc (see Vol t, A450-L)... 

Kilpatrick et al.111 measured the rate of desulphonation of mesitylenesulphonic acid in excess of 12-13.5 M sulphuric acid. The rate coefficients are given in Table 43 (p. 73), and these were determined by spectrophotometrically measuring the concentration of sulphonic acid present at equilibrium, after reacting the sulphonic acid with the sulphuric acid of appropriate concentration again the increase in rate of desulphonation with increase of acid strength is much less than the increase in the rate of sulphonation. The increase in rate of desulphonation of mesitylenesulphonic acid with increasing acid concentration was less than that for 1,2,4,5-tetra-, 1,2,3,5-tetra-, and penta-methylbenzenesulphonic acids703 (Table 244) the... 

The catalyst acidity is determined by the number of acid sites and their acid strength. The total concentration of acid sites, C<, can be obtained from independent TPD measurements. The average acid strength of the sites is characterized by the alkene standard protonation enthalpy,, and is typically determined by regression using reference... 

XL30). Mossbauer spectroscopy (KFKIj was applied to follow the state of Fe species in the zeolites. Carbon monoxide and ammonia adsorption (monitored with FTIR) (EQUINOX 55) was used to determine the nature, concentration and acid strength of the active sites in the Fe-TON zeolites. 

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