Functionalized porous silica microspheres as scavengers in parallel synthesis

The use of solid scavengers in parallel solution-phase organic synthesis is an effective method for work-up and purification. Functionalized macroreticular or gel-form polystyrene particles are generally used for scavenging applications, how ever these materials have some limitations. We have developed new scavenging reagents based on ultrapure silica microspheres displaying a variety of functional groups useful for sequestering impurities from reaction products. These materials are easy to handle, have excellent mass-transfer properties, and are efficient scavengers in both polar and nonpolar organic solvents. The properties of these materials were tailored specifically to fit the needs of a medicinal chemist employing parallel synthesis techniques in current commercial equipment. Results are presented from head-to-head comparisons with conventional scavengers in tests designed to demonstrate the versatility of these new materials.     

Complexation and rate of polymerization of acrylic acid and methacrylic acid in the presence of poly(4-vinylpyridine) in dilute methanol solution

A 1:1 hydrogen-bonded complex was formed between acrylic acid (AA) or methacrylic acid (MA) and the pyridine group of poly(4-vinylpyridine) (P4VP) in dilute solutions. A shift of infrared absorption of the hydrogen-bonded acid O? H to a lower energy direction and an upfield shift of acid proton in the NMR were observed when the monomers were added with pyridine. The equilibrium constants of the 1:1 complexation with P4VP measured by using a semipermeable membrane were 0.58 and 0.26 for AA and MA, respectively, at 25°C in methanol. The bromometrically measured initial rate of radical polymerization showed only a slight enhancement in the presence of P4VP, the rate being maximum at the 4VP unit:monomer mole ratio of 0.25 and 0.5 for AA and MA, respectively, in dilute methanol solution at 60°C.     

The thermoelastic effect in glassy polymers

The thermoelastic effect has been measured in compression on four glassy polymers; namely, polystyrene, poly(methyl methacrylate), polycarbonate, and epoxy resin. Quantitative results have been obtained for the first time on three of these polymers. It has been shown that by paying attention to specimen geometry and instrumentation results can be obtained to a high degree of accuracy (better than ±1.5% on a given set of measurements). The polymers are shown to obey the classical Thompson equation for thermoelasticity in solids over the temperature range studied (ca. 220–350°K). By inference such materials can be expected to behave classically in general. The results have been used, as first suggested by Trainor and Haward, to obtain values for the linear thermal expansion coefficient and the values so obtained are shown to be in excellent agreement, in general, with literature values obtained by more conventional methods. Results are given for a range of stress from 5 MN m^?2 to between 25 and 50 MN m^?2 according to ambient temperature. The method affords a measurement of parameters, in particular, linear thermal expansion coefficient. Values of specific heat for the four plastics have been measured by differential scanning calorimetry and the results compared with published data.     

Calculation of the Grüneisen constant of glassy polymers from thermoelastic data

Thermoelastic measurements on a glassy polymer make it possible to measure directly the quantity αV/C_p where α is the coefficient of linear expansion, V the specific volume, and C_p the specific heat at constant pressure. By further measuring the bulk modulus (B_T) it is possible to derive a relatively accurate value of the thermodynamic Gruneisen constant (γ_T) where γ_T = 3B_TαV/C_v. The values obtained decrease only slightly with temperature.     

The tensor analyzing power Azz AT θ = 0° for the He( , p)He reaction

The tensor analyzing power f_zz has been measured for the ³He( , p)⁴He reaction at 0 = 0° over an incident deuteron energy range E_d = 6.6–15.8 MeV in steps of 0.5 MeV. The present results agree with and extend the previous measurements of Grüebler et al. The present results indicate that this reaction is a very good tensor analyzer for polarized deuteron beams with energies up to 15.8 MeV.     

Study of the centrally producer ππ andK \bar K systems at 85 and 300 GeV/c

We have studied the andK systems centrally produced in proton proton collisions at 300 GeV/c and ⁺/p proton collisions at 85 GeV/c using the CERN spectrometer. Clear evidence forS ^*/f _o(975) production is observed. An analysis performed on the ^{+ –} mass spectrum in the 1.0 GeV region, using a coupled channel formalism, shows that it is possible to describe theS ^*/f _o(975) effect with one single resonance once interference of theS ^*/f _o(975) with theS-wave background is introduced. The resultingS ^*/f _o(975) parameters arem _o =979±4MeV,g =0.28±0.04,g _K =0.56±0.18 corresponding to a pole position on sheet II at (1001±2)–i(36±4) MeV. Evidence is also found for a structure having a mass of 1472±12 MeV and a width of 195±33 MeV.