Dipole Moments, Polarography, and Other Electrical Properties

8 Dipole Moments, Polarography, and Other Electrical Properties 

The dipole moment of tributylpliosphine varies from 1.49 to 2.4 D according to the solvent used. Inductive effects in phosphines have been estimated by comparing the calculated and observed dipole moments, and the apparent dipole moment due to the lone electron pair on phosphorus has been estimated. A method of calculating the hybridization of the phosphorus atom in terms of bond angles is suggested which leads to a linear relationship between hybridization ratio and lone electron pair moment. The difference between experimental and calculated dipole moments for para-substitued arylphosphines, phosphine sulphides, and phosphinimines has been used to estimate mesomeric transfer of electrons to phosphorus. 

Conformational populations of cyanomethylphosphine oxides (136) have been estimated from dipole moments and indicate a preference for the tra/15-conformation. The moments of the o-, m- and p-chloro- and tolyl-derivatives of triaryl phosphites (137, Y = ) and triaryl phosphates (137 Y = O) indicate that the oxygen atom in the latter series causes the aryl rings to rotate further away from a position in which their planes all meet along the molecular symmetry axis. Conformational studies have also been carried out on the dioxaphosphorinanes. The moments of the isomeric series (138a) and (138b) were in the ranges 3.7—4.2 and 5.4—5.5 D respectively.  

Not surprisingly, the dipole moments of 1 1-complexes of phosphines and aluminium chloride are very large. Triethylphosphine also forms a 2 1 complex whose very low dipole moment suggests a symmetrical structure such as (139).  

Polarographic studies are reported on thioesters, mainly of the type (140) and (141), and on trichloroethylphosphonites. In the field of nucleotides and nucleosides it is found that ATP has a very high surface activity at the mercury electrode, which is strongly dependent upon complex formation with transition metals. The polarographic behaviour of cobalt complexes with triphenylphosphine and its oxide has been studied in order to estimate extraction efficiencies. 

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