Bronsted base water

Step 3 in Figure 5 6 shows water as the base which ab stracts a proton from the car bocation Other Bronsted bases present in the reaction mixture that can function in the same way include tert butyl alcohol and hydrogen sulfate ion... 

Notice that because HzO accepts the hydrogen ion to form H30+, water is acting as a Bronsted base in this reaction. 

Another example of a Bronsted base is ammonia. When ammonia dissolves in water, it is protonated when the lone pair of electrons on the N atom accepts a proton from 112( ) ... 

A basic oxide is an oxide that reacts with water to form a Bronsted base, as in the reaction... 

Because water is amphiprotic—because it is both a Bronsted acid and a Bronsted base—proton transfer between water molecules occurs even in pure water, with one molecule acting as a proton donor and a neighboring molecule acting as a base ... 

This reaction shows that the methide ion is a very strong Bmnsted base. The species C22 is the acetylide ion, and the carbides that contain it are called acetylides. The acetylide ion is also a strong Bronsted base, and acctylides react with water to produce ethyne (acetylene) and the corresponding hydroxide. Calcium carbide, CaC2, is the most common saline carbide. 

Ammonia is very soluble in water because the NH3 molecules can form hydrogen bonds to H20 molecules. Ammonia is a weak Bronsted base in water it is also a reasonably strong Lewis base, particularly toward d-block elements. For example, it reacts with Cu2+(aq) ions to give a deep-blue complex (Fig. 15.4) ... 

Subsequently, Bos and Dahmen used in m-cresol65 (e = 12.29 at 25° C) a potentiometric titration method combined with conductometry. Essential precautions were the preparation of water-free m-cresol (<0.01% of water), the use of a genuine Bronsted base B, e.g., tetramethylguanidine (TMG), and the application of a glass electrode combined with an Ag-AgCl reference electrode filled with a saturated solution of Me4NCl in m-cresol. The ion product of the self-dissociation of m-cresol, Ks, was determined from the part beyond the equivalence point of the potentiometric titration curve of HBr with TMG comparison with titration curves calculated with various Ka values showed the best fit for Ks = 2 10 19... 

A water molecule acting as a Bronsted base accepts a proton from the fert-butyloxonium ion. 

Because of its high negative charge density, the oxide ion is a very strong Bronsted base. Therefore, when an ionic oxide is placed in water, there is proton transfer to produce hydroxide ions. 

In this reaction, hydrochloric acid (HCl) donates a proton to water (H2O), making it the Brpnsted-Lowry acid. Water, which accepts the proton, is the Bronsted-Lowry base. This makes hydronium (H3O+) the conjugate acid and chloride (Cl ) the conjugate base. Water can act as the base in this reaction and as an acid in the example problem because it s composed of both a hydrogen ion and a hydroxide ion therefore, it can either accept or donate a proton. 

An example of a Bronsted base is an oxide ion, such as the oxide ion in calcium oxide, CaO. When CaO dissolves in water, the strong negative charge of the small O2- ion pulls a proton out of a neighboring HzO molecule (Fig. 10.4). By accepting a proton, the oxide ion has become protonated. The oxide ion (a Lewis base, Section 2.13) forms a coordinate covalent bond to the proton (a Lewis acid) by providing both the electrons in the bond and becomes a hydroxide ion ... 

Limestone is composed primarily of calcium carbonate. A 1.0-mm3 chip of limestone was accidentally dropped into a water-filled swimming pool, measuring 10m X 7m X 2 m. Assuming that the carbonate ion does not function as a Bronsted base and that the pH of the water is 7, will the pebble dissolve entirely The density of calcium carbonate is 2.71 g-cm 3. 

The carbide ion ( C=C 2 ) is a Bronsted base and is readily protonated by water, resulting in the formation of the organic compound ethyne (acetylene) ... 

Because PH3 is the very weak parent acid of the strong Bronsted base P3, we can form phosphine by protonating phosphide ions with a Bronsted acid. Even water is a sufficiently strong proton donor ... 

Water can act as a weak Bronsted acid, a weak Bronsted base, a... 

A Bronsted base can accept a proton from water to give hydroxide ion (OH ). 

HF transfers a proton to water. Therefore HF is the Bronsted acid and H2O is the Bronsted base. But in the reverse direction, hydronium ions transfer a proton to fluoride ions. H30+ is the conjugate acid of H2O because it has an additional proton, and F is the conjugate base of HF because it lacks a proton. 

C Choice A is the definition of a strong acid, choice B is the definition of a Lewis acid, and choice D is the definition of an Arrhenius acid. By definition, all Arrhenius bases form OH- ions in water, and all Bronsted bases are proton acceptors. But not all Bronsted bases use OH- as a proton acceptor. NH3 is a Bronsted base for example. 

It is a good Lewis base. It acts as a monodeutate big and forms complexes. In water it acts as a Bronsted base. 

The correct answer is (C). HzO accepts a proton from HC2H302. Proton acceptors are Bronsted-Lowry bases. Water can act as a Bronsted-Lowry acid or base, but in this reaction it is a base. 

Bronsted bases, ions or molecules that will take on protons, are generally negative ions or neutral molecules there are a few of such bases that are positively charged, the most important being hydrated cations that have lost protons, for example, Zn(H20)3(0H)+. Basic half-reactions of the hydroxide ion, the sulfate ion, the oxide ion, water, the hydrogen carbonate ion, and the zinc-containing cation, mentioned above, are listed ... 

The eventual collision between H30+ and a negative center regenerates then the water molecule and destroys the negative ion. Hence, (H20)2 or higher agglomerates react with carbonium ions as Lewis bases, alcohol is formed, and one water molecule is destroyed. Therefore, the termination of polymerization proceeds simultaneously with the destruction of the terminator. However, at very low water concentration, the single H20 molecule eventually reacts as a Bronsted base—i.e., as a proton acceptor (Reaction 4). In this process the polymerization is terminated, but the terminator is not destroyed. This accounts for the experimental results—viz., the last trace of moisture cannot be removed from the monomer by prolonged irradiation (24, 37). 

The dominant characteristic of O2 in any medium is its ability to act as a strong Bronsted base to form HOO-, which reacts with itself or a second 02 - (Scheme 1). Within water, superoxide ion is rapidly converted to dioxygen and peroxide (equation 27). 

Reduction by electron transfer yields superoxide ion (02 -)> which has its negative charge and electronic spin density delocalized between the two oxygens. As such, it has limited radical character (H-OO bond energy AGbf, 72kcalmoU ) and is a weak Bronsted base in water... 

Most of the imprinted sorbents used in MISPE were prepared using MAA and ethylene glycol dimethacrylate (EDMA) as monomers. In these cases elution of more weakly bound analytes such as triazines [19,30,32], 7-hydroxy-coumarin (2) [26] or theophylline (12) [28] can be achieved using methanol or water as elution solvent. For more strongly bound analytes such as stronger nitrogen Bronsted bases, efficient elution has been achieved using eluents of the same base solvent but with the addition of small amounts of acids (e.g. acetic acid, trifluoroacetic acid (TEA)) or base (e.g. triethylamine (TEA)) [20-22,25,33]. 

Lewis acid and Bronsted bases. Thus, Bronsted acid sites are responsible for the catalytic cracking of cumene. The quinoline does not react with the Lewis acid sites at 325°C but only with the Bronsted acid sites. Furthermore, for samples whose pretreatment temperature is equal or less than 400°C, the number of active sites is 8.3 X 10 . This value is to be compared with 9.9 X 10 /gram calculated from stoichiometry, assuming 25 wt % of water and ammonia as determined by Turkevich and Ciborowski. 

The properties of superoxide anion have been well reviewed [45,46]. In water it is a relatively weak nucleophile, whereas in aprotic solvents, such as those commonly used for electrolysis, it is a powerful nucleophile. Its basic properties stem from the driving force of the disproportionation [45,46] depicted as Eq. (5), similar to the disproportionation discussed for organic radical anions in Sec. II.B. Thus, although superoxide anion itself is a relatively weak Bronsted base— pA a(H02) 12 in DMF [46]—the overall equilibrium... 

The temperature conditions under which Bronsted acid sites are converted into Lewis acids have been determined in the Princeton laboratories. It was established that the ammonium zeolite completely decomposes at about 340° and leaves protonic acid (Bronsted sites) on the surface. When such a material is heated to over 480°, the protons are removed as water, two Bronsted acid sites producing one Lewis acid site and a Bronsted base site. It was thought desirable to determine which of these acidic sites were responsible for cracking of cumene and to extend the investigations to the study of the cracking of a more demanding molecule, in the sense of Boudart, i.e., 2,3-dimethyl-butane. 

Decationation of the process of conversion of the Bronsted to Lewis acid sites that takes place in the temperature range of 400-500° as a result of the evolution of water can be visualized as shown in Fig. 8. The Bronsted acid sites are shown by (A), the Bronsted base by (B), and the Lewis acid site by (C). The specific molecular locale of the Lewis acid site is the three-coordinated aluminum. It can act as an acceptor of H or of one electron. As an acceptor of the H ion it may play an important role in initiating the carbonium type of reactions of the hydrocarbons by facilitating carbonium ion formation. On the other hand, it is also an electron acceptor. Turkevich and Stamires have shown this when they studied the ESR of triphenylamine (an electron donor) on a variety of zeolites. They found that the amount of electron transfer increased... 

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