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The molecular exchange of dimethyl methylphosphonate (DMMP) between the reactive and sorptive components in a mixture of three macroreticular resins (a high surface area carbonaceous adsorbent and strong-base and strong-acid ion-exchange resins) is characterized by 31 P MAS NMR. Data from 31 P MAS magnetization-transfer NMR experiments performed on four samples possessing 2,6,9 and 14% DMMP are analyzed using a modified two-site exchange model which takes into account that only a fraction of DMMP molecules adsorbed on the carbonaceous adsorbent (site B) are able to exchange with those residing on the ion-exchange resins (site A) during the time scale of the experiment. The exchange lifetime determined in this manner for DMMP adsorbed on the carbonaceous adsorbent ( k −1 B ) remains fairly constant at ca. 50 ms for the four samples. The exchange lifetime for DMMP residing on the ion-exchange resins ( k −1 A ) is observed to increase for lower weight-percent loadings: 250 ms (14%), 330 ms (9%), 500 ms (6%) and 670 ms (2%). 31 P MAS 2-D exchange NMR experiments indicate an optimum mixing time (τ m ) of 0.2–0.5 s for the 14% sample, which is consistent with the measured exchange lifetimes.

A powder containing sorptive and reactive resins that was developed for the removal and subsequent catalytic degradation of toxic organophosphorus esters is characterized using dimethyl methylphosphonate (DMMP), p-nitrophenyl diphenylphosphate (PNDP), and 31P MAS NMR. The results for DMMP confirm, spectroscopically, that the adsorbed ester is distributed between the sorptive and reactive resin components. Spectra of the DMMP surface probe adsorbed on the resin are indicative of two different adsorption sites, one possessing a much larger capacity compared with the other. The large-capacity site is identified as the sorptive macroreticular ‘porous’ region of the resin. The smaller-capacity site seems to be associated with the reactive quaternary ammonium hydroxide functional groups of the ion-exchange resin. At each type of site, adsorbed DMMP exhibits ‘liquid-like’ isotropic motion; however, the molecules do not appear to be able to rapidly migrate between the sorptive and reactive regions. Variable-temperature 31P MAS NMR results for DMMP demonstrate that any molecular exchange between these sites must be occurring at a rate of less than 300 s−1, even at 50 °C. PNDP hydrolyzes on the resin powder to yield diphenyl phosphate (DPP) and p-nitrophenoxide. A second 31P MAS NMR resonance is not observed for PNDP adsorbed at the reactive sites; however, the anionic DPP product appears to be tightly bound by the quaternary amine ion-exchange group, which may block further PNDP hydrolysis at the reactive site.

The tertiary amine, N -2-hydroxyethylpiperazine- N '-2-ethanesulfonic acid (HEPES) is a common buffer used in measuring the hydrolysis of neurotoxins such as the phosphonofluoridates soman and sarin. The hydrolysis of soman was monitored in the presence of various concentrations of HEPES at 25 °C and pH= 7. The rate of hydrolysis of soman was linearly related to the concentration of HEPES present as free base in solution. The second-order rate for the HEPES catalysis was 1.6 × 10 −3 M −1 s −1 , in contrast to a value of 10 M −1 s −1 for the hydroxide ion-catalyzed nucleophilic attack on soman.

Neat droplets of O,O-diisopropylphosphorofluoridate (DFP) and O-1,2,2-trimethylpropyl methylphosphonofluoridate (Soman) decompose on glass. In thirty hours at room temperature over 40% of the Soman has been decomposed while nearly 15% of the DFP has been degraded. NMR spectroscopic analysis of the Soman showed that Soman decomposed exclusively by scission of the PF bond to form O-1,2,2-trimethylpropyl methylphosphonic acid. The rate of decomposition of the two organophosphorus fluorine substrates is proportional to the rate of hydrolysis. The results are consistent with earlier studies which showed that silica or magnesia promoted the decomposition of sarin (O-2-propylisopropyl methylphosphonofluoridate). The rate of decomposition on glass is accelerated in the presence of high humidity.

The syntheses of five new 4-alkyl-2-iodosobenzoic acids (3) are described. The iodine atom was introduced by ortho-directed lithiation of 4-alkylbenzyl alcohols followed by treatment with I 2 . The catalytic effectiveness of each of the products in the hydrolysis of 4-nitrophenyl diphenyl phosphate in microemulsions was studied. The 4-methyl- and 4-ethyl-substituted products were each found to be significantly better catalysts than the standard nonalkylated 2-iodosobenzoic acid (3, R = H). These results would indicate that microemulsions of these materials may find use in detoxification procedures

Organophosphonofluoridates [CH 3 (OR)P(O)F] are potent neurotoxins. In aqueous solutions these compounds hydrolyze to release fluoride and form the corresponding O -alkyl methylphosphonic acid. Recently we examined the hydrolysis of O -isopropyl t -butylphosphonofluoridate ( I ) which was reputed to be relatively nontoxic relative to O -isopropyl methylphosphonofluoridate (sarin). The hydrolysis of I was measured with 31 P NMR at 20°C in buffered solutions with pH values of 4.0, 7.2, 9.2, and 10.0, respectively. At pH 10, I hydrolyzed approximately 4000 times slower than sarin. In addition I hydrolyzed by parallel reaction paths producing both O -isopropyl t -butylphosphonic acid and t -butylphosphonofluoridic acid. Below pH 9, the latter product predominates. To our knowledge this is the first example of parallel hydrolysis paths above pH 7 for a phosphonofluoridate.

Transition metal ions, such as manganese(II) or copper(II), catalyze the hydrolysis of O -isopropyl methylphosphonofluoridate (sarin) or O , O' -diisopropyl phosphorofluoridate (DFP). The rate law for the catalyzed path is first order in ester, metal(II) and hydroxide. Thus, the catalytic species could be the hydroxometal complex, or the catalysis could consist of a complex formed between the metal ion and phosphorus substrate which is subsequently attacked by hydroxide. Recently, we measured the solvolysis of sarin in an ethanol-water solution. By means of 31 P nuclear magnetic resonance (NMR), two products were seen to form from parallel attack on sarin by hydroxide and ethoxide. In the presence of zinc(II) chloride, it was shown that both reaction rates were significantly increased. If the increase in reactivity were attributed to a zinc hydroxide complex, then no change would be expected in the rate of attack by ethoxide ion. We further suggest the monitoring of relative rates of reaction in mixed solvents as a way to distinguish whether a metal ion catalyst acts as a Lewis acid or simply supplies a larger concentration of nucleophilic hydroxide ion.

Mustard, bis-(2-chloroethyl) sulfide, hydrolyzes to form the mustard chlorohydrin with concomitant loss of chloride; the chlorohydrin subsequently hydrolyzes to form the mustard diglycol with loss of another chloride ion. The kinetics of these reactions constitutes two consecutive, irreversible reactions. Past investigators approximated the hydrolysis as a single, first-order reaction from which an activation energy was determined. Bartlett and Swain measured the rate of mustard chlorohydrin hydrolysis after which they could determine the rate of mustard hydrolysis with a graphical method. Bartlett and Swain performed their experiments at 25°C, so no activation parameters were measured. A non-linear least-squares program was modified to fit consecutive, irreversible first-order kinetics and refit original data for mustard hydrolysis in order to find activation parameters for each step. The data failed to conform to consecutive, first-order kinetics suggesting that either sampling error or failure to dissolve rapidly interfered with the kinetics. Thus, the activation parameters for mustard hydrolysis are incorrect not only for the single-step approximation, but also because systematic experimental errors must be present. Rate coefficients computed with Bartlett and Swain's data were statistically equivalent to their reported value of 0.155 min −1 .

The equilibrium constants derived by Postmus and King were treated with Blandamer's expression to test the temperature-dependence of Δ C 0 p for the formation of the thiocyanatopentaaquochromium(III) ion. The results revealed temperature-dependent enthalpies and temperature-independent Δ C 0 p (66 Cal mole −1 K −1 ) implying that the equilibrium constant for association of Cr(H 2 O) 5 NCS 2+ represents a unitary process.

The kinetics of the hydrolysis of 1,2-2-trimethylpropyl methylphosphonofluoridate (soman) was measured from 1 to 80 × 10−5 m hydroxide-ion concentration. No apparent “saturation effect” could be positively identified such as was reported by Martell for the hydrolysis of isopropyl methylphosphonofluoridate (sarin). The second-order rate coefficient for soman was 10.0 ± 0.03 m −1 s−1 at 25.0°C over this pH range.

The kinetics of the dehydroxylation of talc have been measured in the temperature interval 1100–1160 K by means of isothermal weight-change determinations. The reaction follows first-order kinetics. Over the indicated temperature range the enthalpy of activation was found to be 101±4 kcal mol−1, and the entropy of activation was found to be 16±4 cal mol−1 K−1. The error estimates correspond to one standard deviation. The enthalpy necessary to break the MgOH bond was estimated from the heat of reaction for MgOH(g) → Mg(g)+OH(g). This turns out to be 97 kcal mol−1 in reasonable agreement with the measured enthalpy of activation. These activation parameters are consistent with the mechanism proposed for dehydroxylation of talc consisting of MgOH bond scission and subsequent migration of magnesium. These results contradict a previous report on the kinetics of talc dehydroxylation in which a diffusion-controlled expression was claimed to represent the rate of talc weight loss. It is suggested that the presence of adsorbed water on the talc used in the previous investigation is responsible for the discrepancy.

Hydrolyse du sulfure d'ethyle et de chloro-2 ethyle et du sulfure de methyle et de chloro-2 ethyle. Comparaison a l'hydrolyse du chlorure de t-butyle. Mise en evidence d'un mecanisme S N 1 avec assistance anchimere de l'atome de soufre pour former un ion sulfonium cyclique comme intermediaire de reaction

Gas chromatography-mass spectrometry under both electron impact and methane chemical ionization conditions has been used to detect impurities and degradation products present in the mustard simulant 2-chloroethyl ethyl sulfide, with a detection limit of 0.05 area percent. After one and two years of storage at ambient temperatures, the primary degradation product was 1,4-dithiane formed from the degradation of dimeric sulfonium ions. Oxidation and hydrolysis products were not detected.

Wear-reducing liners such as polyurethane foam and TiO 2 -wax liners have markedly extended the useful life of 105 mm tank cannons. The wear life of 100 rounds without additives has been extended to 400 rounds with polyurethane foam and 10000 rounds with TiO 2 -wax liners in a flapped configuration suggested by the Swedish inventors of the TiO 2 -wax liner. When the TiO 2 -wax liner is placed in fin-stabilized rounds the liner is glued to the cartridge case wall without the flaps; the presence of fins precludes any other modification. The TiO 2 -wax liner in the fin-stabilized round improves cannon life from 100 to 1000 rounds. To discern the differences observed for the liners heat transfer measurements were made with thermocouples embedded in the barrel wall to within a millimeter of the bore surface. The reduction in heat transfer relative to standard rounds with the additives removed showed that the flapped configuration is more efficient than simply lining the case wall. In repeated firings of rounds with TiO 2 -wax additives it was observed that the heat input to the barrel steadily decreased during the first 13 rounds fired after which the heat input remained steady. This is attributed to the formation of an insulating layer on the bore surface and accounts for the higher wear life of the TiO 2 -wax liner relative to the polyurethane foam liner when used in the same configuration. It was also demonstrated that a talc-wax liner with the same dimensions as a TiO 2 -wax liner should produce improved wear life for finstabilized projectiles fired from the 105 mm tank cannon.

Three aqueous samples containing sulfonium chloride salts of both mustard gas (2,2′-dichlorodiethyl sulfide) and its simulant 2-chloroethyl ethyl sulfide have been characterized by gas chromatography/mass spectrometry (GC/MS). These salts decompose thermally to the corresponding 2-chloroethyl and 2-hydroxyethyl sulfides, therefore GC/MS analysis is not indicative of the true composition of these solutions. Small amounts of dithioethers characteristic of the decomposition of the dimeric salts were also detected. Electron Impact (EI) ionization produces a more intense molecular ion than methane chemical ionization (CI) for the dithioethers because of the ease of formation of sulfonium ions during chemical ionization. The decomposition products of four aged samples of 2-chloroethyl sulfides (RSCH2CH2,Cl where R = methyl, ethyl, phenyl and benzyl groups) were also characterized by GC/MS, which indicated that decomposition of these compounds may proceed via dimeric sulfonium ions. Mustard gas was dete...

The burning rate of pressed strands made from a stoichiometric mix of magnesium and sodium nitrate was measured in nitrogen over the pressure range 0. 1 to 8.6 MPa. A plot of the logarithm of burning rate vs logarithm of pressure reveals two distinct regions with the 'slope break' occurring near 2 MPa. At the lower pressures, the slope is 0.3; at higher pressures, the slope is 0.05. The burning rate measured at 3.4 MPa was unchanged when oxygen replaced nitrogen; thus, gas-phase reactions do not affect the burning rate.

Swain and co-workers at MIT recently composed a 92-statement FORTRAN computer program to evaluate first-order rate coefficients from kinetic data. The

The specific heat of gun propellants is an important physical parameter, since the burning rate of such materials depends, in part, on the thermal diffusivity of the unaltered solid. In order to support combustion modeling work, the specific heat vs temperature of a typical double-base propellant and four grades of cellulose nitrate were measured with a commercial differential scanning calorimeter, since measured specific heats were unavailable for these materials. The specific heat of the four military grade cellulose nitrates was measured from 298 to 390K. Over this temperature range, the specific heat of each grade may be represented as follows: Grade B, C¯p= (0.0184 + 0.764⊝) cal/g-K; Grade C (Type I), C¯p= (0.0201 + 0.786⊝) cal/g-K; Grade C (Type II), C¯p= (0.0241 + 0.791⊝) cal/g-K; and Grade D (Pyroxylin), C¯p= (0.0256 + 0.817⊝) cal/g-K, where ⊝ = T/1000K. The specific heat of X14 propellant was measured over the temperature interval of 283 to 343K. The specific heat of X14 can also be represented by the same two-term equation as the cellulose nitrates. For X14 the specific heat is C¯p= (0.118 + 0.066⊝), cal/g-K with ⊝ = 1000/T.

This report summarizes the third set of wind tunnel tests to evaluate the effect of combustion of pyrotechnics on the base drag of supersonic projectiles. In this test series, a larger diameter model was used to expand the range of injection parameters for R20C. It was found that the base pressure rise vs I, the injection parameter, for R20C could be correlated by an expression requiring two parameters. The maximum base drag reduction achieved with pyrotechnics at M sub infinity = 2.0 was 68%. The maximum specific impulse at M sub infinity = 2.0 was nearly 8kN-s/kg. The maximum specific impulse was observed at an I value of 0.002. Direct measurement of the specific impulse by means of a force balance agreed with the specific impulses computed from integrating base pressure-time histories.

obtain a straight line for the portion of the curve which ought to be in the logarithmic region and plays no role in the model used to compute turbulent flows. To obtain the skin-friction coefficient from the slope of the straight-line portion of the curve, it is customary to assume that the von Karman constant retains its value for flows over smooth surfaces (see Ref. 2, p. 177). It is thus seen that the argument for parallel log-law portions for smooth and rough flows is an essential part of bringing the experimental data into tractable form. The shift Ay + employed by Rotta is simply the difference between the smooth and rough log-law portions of the curves on semilog plot as u + vs y + (see Fig. 4.29 and 4.30 of Ref. 1) and bears no relationship to the shift of virtual origin Az. The virtual origin y = 0 is a distance Az below the crests of the roughness elements. The y in Eqs. (7) and (9) in Mills paper are indeed measured from the virtual origin. Thus the contradiction in the eddy-viscosity formulas and the wall boundary conditions *'invented" by Mills does not exist. The appearance of Ay in Eq. (7) only affects the rate of approach to Eq. (9) when performing integration. However, this problem has been clearly overshadowed by the questions of where to start the solution and what the boundary conditions should be because the sublayer is reduced or nonexistent. It has been found by experience that the logarithmic boundary conditions, Eq. (9), are satisfactorily applied if >>^>50 and u0/ue >0.15 are satisfied simultaneously. Mills' objection 2 toward the end of his Comment simply states the obvious: Of course we are well aware that Eqs. (8) and (10) will have different forms for different roughness geometries (see Ref. 1, p. 129, Fig. 4.27). Unfortunately, so far only the sand-grain type roughness has been well researched and documented. Before we conclude, we would like to offer a word of caution. If the agreement between "theory" and all the available experimental data on the subject is quite good (so good that it may be difficult to beat these predictions by other turbulence models), it is perhaps advisable to be cautious in light of this agreement before raising objections which do not bear up under the weight of the theoretical, computational or experimental evidence.

Hydrolyse des bis-[chloro-2 ethyl] sulfure, chloro-2' ethylthio-2 ethanol en presence de thio-2,2' bis-ethanol. Identification par les spectres RMN 13 C des composes sulfonium obtenus

The kinetics of the thermal degradation of a rigid polyurethane foam used to reduce gun wear was determined to illustrate how Guggenheim's method could be applied to polymer decomposition. The polyurethane foam decomposed in two distinct steps. The first order activation parameters for each rate coefficient are k sub 1 = 2.0x10 to the 10th s -1EXP(-134kJ/mole/RT) and k sub 2 = 1.2x10 to the 10th s -1EXP(-154kJ/mole/RT).