Mitsuo Mashima

Ultrasonic relaxation in aqueous solutions of butanediols

Ultrasonic absorption and velocity have been measured to investigate the structural and dynamic properties of aqueous solutions of butane-1,4-diol and butane-1,2-diol at 20 °C. In the former solution no excess absorption was found, and in the latter solution a single relaxational process was observed in the frequency range 15–220 MHz. The excess absorption mechanism has been analysed as a solute–solvent interaction, AB ⇌ A + B, and the rate constants for butane-1,2-diol solution have been determined to be kf= 1.5 × 108 s–1 and kb= 1.6 × 108 dm3 mol–1 s–1 for the forward and backward steps, respectively. The influence of the position of hydroxy groups in the molecules on the water structure is discussed by a comparison with the results for solutions of the two dihydric alcohol.

Directed Valence in P4 and As4

It has been reported that three best spd hybrid bond orbitals may be constructed at mutual angles of 73°9′ and 133°37′, but these bond orbitals have not been adapted to actual molecules. We can obtain trigonal pyramid bond orbitals which have mutual angles of 73°9′ and strength 3. When an angle between the directions of three equivalent bond orbitals is introduced as a parameter to these bond functions, variation of strength of these bond orbitals with the angle may be illustrated. These hybrid bond orbitals may be adapted to P4 and As4. It is reported that P4 and As4 molecules have bond angle 60°, the four atoms lying at the tetrahedron corners and the bonds along the tetrahedron edges. Hultgren has applied pd hybrid bond orbitals to such a configuration. Assuming that the s orbital is used in hybridization, we can obtain stronger bond orbitals than that by pd hybridization. Such spd trigonal pyramid bond orbitals have strength 2.970 (only slightly less than that of the best spd hybrid bond orbital) at b...

Study of the structural properties of organic mixed solvents by ultrasonic methods

Ultrasonic absorptions and velocities in mixtures of acetic acid-chloroform and trifluoroacetic acid-chloroform have been measured at 25°C. The excess absorptions are interpreted in terms of the reaction kinetics associated with the breakage and formation of hydrogen bonds using a linear free-energy relation. Unusual ultrasonic relaxation properties have been attributed to the free-energy difference between the open dimer and cyclic dimer of the acid. The NMR chemical shifts have also been measured for the mixtures in order to ascertain the interaction between the acid and chloroform. The results are compared with those obtained from the ultrasonic absorption data.