Solvent Effect on the Isotopic Ratios vo OH/vOD and AOH/AOD in a Tetrachlorosubstituted Mannich Base

Mannich bases are compounds formed from phenols and amines, characterized by intramolecular hydrogen bonds whose strength depends on the substituent implanted on the phenol ring; moreover, as shown by uv measurements, the strength of the interaction for a given phenol derivative depends strongly on the solvent In this work, we have studied the ir spectra of 2,3,4,5-tetrachloro-6-[(diethylamino)methyl]phenol (TCMBH)     

Crystal and molecular structure of cyclo-(S-prolyl-R-N-hydroxyphenylglycyl), C13H14O3

The structure of the title compound, C₁₃H₁₄N₂O₃, was determined by X-rays.M _r =246.26, orthorhombic, space group P2₁2₁2₁,a=6.809(1),b=10.041(2),c=17.571(2) Å,V _c =1196.5 ų,Z=4,D _x =1.36 Mg m^–3. MoK radiation (graphite crystal monochromator, =0.71069 Å),(MoK)=1.06 cm^–1,T=290 K. Final conventionalR-factor=0.037,R _w =0.039 for 1377 unique reflections and 205 variables. The structure was solved usingMultan. The synthesis of the title compound involved a ring-closing reaction with an optically pureN--halophenylacetyl-(S)-proline methyl ester of known absolute configuration. From this the absolute configuration of the title compound could be determined, and it could be proved that the reaction proceeds according to anS _N 2 process.     

2-D PIV measurements of oscillatory flow around parallel plates

Oscillatory flow in stacks of parallel plates is essential for the working of “standing wave” thermo-acoustic devices. In this paper, the flow in the transition from stack to open tube is studied experimentally using particle image velocimetry. When the flow is directed outwards of the stack, vortices originate behind the stack plates. The Strouhal to Reynolds ratio determines the vortex pattern behind the stack plates, varying from a single vortex pair to a complete vortex street. The influence of different plate-end shapes and porosities are also studied. The streaming velocity is measured using two different methods.     

Studies in Cyclocopolymerization. IX. A Systematic Kinetic Study on the Cyclocopolymerization of Vinyl Ethers with Maleic Anhydride in Different Solvents

Abstract

The kinetics of the AIBN-initiated copolymerization of divinyl ether (DVE) and ethyl vinyl ether (EVE) with maleic anhydride (MA) was extensively studied in seven different solvents. The yield at 100% conversion as a function of the feed composition when the total monomer concentration is kept constant gave a confirmation of the composition of these copolymers: DVE/MA=½ and EVE/MA=1/1. The study of the initial rate as a function of the feed composition made it possible to determine the relative values of the different propagation rate constants consistent with a mechanism by successive and selective additions: in the EVE-MA system, the addition of EVE is slower than the addition of MA; in the DVE-MA system, the addition of DVE is slower than the addition of the first MA molecule, while the addition of the second MA molecule is slower than the first one. The study of the dependence of the monomer concentration, of the AIBN concentration, and of the efficiency of the initiator, on the rate of polymerization, shows finally that the true order of the monomer concentration is close to 1 while its apparent order varies from 1 to 2. From all the kinetic data it was observed that the mechanism of these co polymerizations can be explained without reliving upon the concept of participation of the charge-transfer complex formed between the monomers. However, participation of the complex in a competing mechanism with the above cannot be completely excluded.