J. R. Van Wazer

Some ab initio LCAO-MO-SCF studies of the electronic structure of cyclopropaneag]

Abstract Ab initio LCAO-MO-SCF calculations have been carried out on cyclopropane, using three different uncontracted Gaussian basis sets. When employing only s and p orbitals, the results were close to those obtained in the other recent quantum-mechanical studies dealing with this molecule. Addition of d character caused pronounced changes in a pair of degenerate molecular orbitais describing the CC bonds. The-dimensional electron-density plots are presented for these orbitals as well as for the total molecule. In addition, an ab initio LCAO-MO-SCF calculation was carried out on butane, the geometry of which was chosen so that the two middle carbon atoms and their four associated hydrogens exhibited exactly the same coordinates as those of a C 2 H 4 segment ofcyclopropane, A difference plot between these two molecule segments demonstrates the existence of “bent bonds” in cyclopropane as well as a build up of electronic charge in the center of its ring.

An approximation for gaussian d-orbital exponents of second-row atoms for LCAO MO SCF studies☆

Abstract It is demonstrated that the radius corresponding to the shell of maximum electron density for molecularly optimized 3d orbitals of a second-row atom is approximately equal to the same radius for the atom-optimized 3p orbitals. An approximation for expanding a single gaussian d-orbital exponent into a larger set of exponents is also offered.

Exchange and condensation of chloro and methoxyl groups between monomethylphosphino and methyl-substituted silyl or germyl moieties

Abstract The room-temperature reaction between CH 3 PCl 2 and (CH 3 ) x M (OCH 3 ) 4−x , where M = Si with x = 2 or 3, or M = Ge with x = 2, exhibits rapid exchange of chloro methoxyl groups between the starting compounds followed by condensation of the phosphorus moieties to give CH 3 (O)P units connected by PP bonds in the resulting oligomers. When CH 3 P(OCH 3 ) 2 is reacted with (CH 3 ) xitx SiCl 4− x for x = 2 or 3, there is no rapid exchange of chloro and methoxyl groups between the reagents but instead the major observed reaction is a slower condensation of the phosphorus moieties, a process which is necessarily accompanied by a transfer of methoxyl groups from the phosphino to the silyl moiety. In the case of CH 3 P(OCH 3 ) 2 plus (CH 3 ) 2 GeCl 2 , there is essentially no reaction in 2 weeks at room temperature except for a slow rearrangement of the phosphorus compound to (CH 3 ) 2 P(O)OCH 3 .