Proton protonated phosphorous

Nucleic acids, DNA and RNA, are attractive biopolymers that can be used for biomedical applications [175,176], nanostructure fabrication [177,178], computing [179,180], and materials for electron-conduction [181,182]. Immobilization of DNA and RNA in well-defined nanostructures would be one of the most unique subjects in current nanotechnology. Unfortunately, a silica surface cannot usually adsorb duplex DNA in aqueous solution due to the electrostatic repulsion between the silica surface and polyanionic DNA. However, Fujiwara et al. recently found that duplex DNA in protonated phosphoric acid form can adsorb on mesoporous silicates, even in low-salt aqueous solution [183]. The DNA adsorption behavior depended much on the pore size of the mesoporous silica. Plausible models of DNA accommodation in mesopore silica channels are depicted in Figure 4.20. Inclusion of duplex DNA in mesoporous silicates with larger pores, around 3.8 nm diameter, would be accompanied by the formation of four water monolayers on the silica surface of the mesoporous inner channel (Figure 4.20A), where sufficient quantities of Si—OH groups remained after solvent extraction of the template (not by calcination). 

In another example, the formation89 of racemic 1,4-anhydroribitol by the action of dilute hydrochloric acid for 20 hours at 100° on D-ribitol 1-phosphate has likewise been assumed to take place by protonation of the oxygen atom of the ester function, followed by an intramolecular substitution by the hydroxyl group on C-4. Formation of this protonated phosphoric ester likewise explains the ra-cemization observed, caused by partial migration of the ester group at C-l to C-5. 

Figure 3. H-NMR (400 MHz) of compound X isolated from a K329A reaction mixture by chromatography on MonoQ. The chemical shifts and proton-proton coupling assignments, based on selective decoupling and 2D experiments (not shown), are consistent with the structure of 2-carboxytetritol 1,4-bisphosphate (inset). Two phosphorous resonances were observed by 3 P-NMR proton-phosphorous couplings, assigned by broad-band decoupling and 2D heteronuclear COSY experiments (not shown), are also consistent with the proposed structure.

By use of SIM, the selectivity and thereby the sensitivity of the MS for organophosphates can be enhanced. For alkylated phosphates, no or very weak molecular ions are observed, while a m/z 99 fragment corresponding to protonated phosphoric acid can be considered to be characteristic. Due to the extensive fragmentation of alkylated phosphates using GC-MS-EI, it is often necessary to apply the GC-MS-PICI technique for identification. Arylated phosphates, on the other hand, exhibit an intense molecular ion and do not show the fragment of m/z 99 in its MS-El spectra. 

From this spectral pattern one may only obtain the averaged value for proton-phosphorous ppH = 37.0 Hz) and proton-platinum (Jp = 500.4 Hz) coupling constants. 

Population analysis of these conformers shows that the effect of an oxygen lone-pair app to a phosphorus-oxygen single bond is to decrease the overlap population of this bond by approximately 40 millielectrons per app lone-pair interaction. Bond order is approximated by overlap population. This result was therefore seen as confirmation of the presence of an anomeric effect in phosphorus chemistry. In addition, the same observation was made in the the presence of d-orbital functions and in calculations on trimethyl phosphate and protonated phosphoric acid. 

Fragmentation Maxima due to alkenyl loss from M" " via double H rearrangement, followed by successive alkene eliminations down to protonated phosphoric acid (m/z 99). 

Phosphate adds to the thioester, forming a tetrahedral intermediate that eliminates the thiolate ion to form the mixed anhydride product (Section 16.20). The thiolate ion s leaving propensity is increased by protonation. (Phosphoric acid has pfsTg values of 1.9, 6.7, and 12.4, so two of the groups will be primarily in their basic forms at physiological pH.)... 

Phosphites are converted to protonated phosphorous acid, H4PO3+, and phosphates are converted to phosphoric acid (Hantzsch, 1907, 1908). 

Monoprotic weak acids, such as acetic acid, have only a single acidic proton and a single acid dissociation constant. Some acids, such as phosphoric acid, can donate more than one proton and are called polyprotic weak acids. Polyprotic acids are described by a series of acid dissociation steps, each characterized by it own acid dissociation constant. Phosphoric acid, for example, has three acid dissociation reactions and acid dissociation constants. 

Potassium Phosphates. The K2O—P20 —H2O system parallels the sodium system in many respects. In addition to the three simple phosphate salts obtained by successive replacement of the protons of phosphoric acid by potassium ions, the system contains a number of crystalline hydrates and double salts (Table 7). Monopotassium phosphate (MKP), known only as the anhydrous salt, is the least soluble of the potassium orthophosphates. Monopotassium phosphate has been studied extensively owing to its piezoelectric and ferroelectric properties (see Ferroelectrics). At ordinary temperatures, KH2PO4 is so far above its Curie point as to give piezoelectric effects in which the emf is proportional to the distorting force. There is virtually no hysteresis. 

The O or S atoms in P=0 and P=S groups may act as electron donors although these groups form relatively weak complexes with electron acceptor compounds such as nonpolarizable, more electropositive (ie, hard) acids, including protons (14). Use is made of this property in the recovery of uranium from wet-process phosphoric acid by extractants such as trioctylphosphine oxide [78-50-2] and di(2-ethylhexyl) hydrogen phosphate [298-07-7]. 

Figure 12.17 Schematic representation of proton-switch conduction mechanism involving [U2PO4I phosphoric acid.

As a catalyst sulfuric acid is most often used phosphoric acid, boron trifluoride or an acidic ion exchange resin have also found application. 1,1-disubstituted alkenes are especially suitable substrates, since these are converted to relatively stable tertiary carbenium ion species upon protonation. o ,/3-unsaturated carbonyl compounds do not react as olefinic component. 

Because of this extreme sensitivity, attention shifted to an acidic system, the phosphoric acid fuel cell (PAFC), for other applications. Although it is tolerant to CO, the need for liquid water to be present to facilitate proton migration adds complexity to the system. It is now a relatively mature technology, having been developed extensively for stationary power usage, and 200 kW units (designed for co-generation) are currently for sale and have demonstrated 40,000 hours of operation. An 11 MW model has also been tested. 

The polymerization reaction starts hy protonating the olefin and forming a carhocation. For example, protonating propene gives isopropyl car-hocation. The proton is provided hy the ionization of phosphoric acid ... 

As another test, we may compare two proton transfers for which 0 happens to fall at almost the same temperature. For phosphoric acid Ki passes through a maximum at 43.1°, as shown in Table 13, while Ka for alanine falls at 44.8°, as mentioned above. According to (143) this implies that the ratio Jnm/Jei has roughly the same value in these two... 

A solution containing 0.20 M H3POj, phosphorous acid, is tested with indicators and the H +(aq) concentration is found to be 5.0 X 10 2 M. Calculate the dissociation constant of H3PO3, assuming that a second proton cannot be removed. 

FIGURE 10.21 The fractional composition of the species in phosphoric acid as a function of pH. As in Fig. 10.20, the more fully protonated the species, the lower the pH at which it is dominant. 

Write the stepwise proton transfer equilibria for the deprotonation of (a) phosphoric acid, I I3P04 (b) adipic acid (CH2)4(C00H)2 (c) succinic acid, (CH2)2(COOH)2. 

Benzene itself, when photolyzed in acetic and aqueous phosphoric acids, has been reported to yield photo adducts 31 and 32 respectively (Farenhorst and Bickel, 1966). Protonated prefulvene (33) is suggested... 

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