Relaxation Times, Paramagnetic Effects, and N.Q.R Studies

Relaxation Times, Paramagnetic Effects, and N.Q.R. Studies.—study of the n.m.r. spectra of the phosphetans (95) has shown that the tertiary carbon atoms have Ty values of 0.6—4 s whereas other carbon atoms have longer 

parameters have been used to calculate the electronic properties of the nitrogen atoms in (96 Y = alkyl or halogen). The population of the electron-pair orbital on nitrogen was at a minimum when Y = Br, and the population 

Relaxation Times, Paramagnetic Effects, and N.Q.R. Studies.—A study of the relaxation times of phosphoryl compounds at two magnetic fields, and of the dependence of spin rotation and dipolar interactions upon viscosity and temperature, led to the approximate separation of dipole-dipole, anisotropy, and spin-rotation interactions, and indicated that second-order paramagnetic shielding was dominant. The P relaxation times 7i and Tz were determined for several lipid-water phases. Comparisons of changes of Tg which occur at the transition temperature for dipalmitoyl-lecithin indicated that the relaxation times reflect the mobility of the lipid head-group.  

PH Decoupling of trialkyl phosphites and phosphates by paramagnetic reagents only occurs when there is direct co-ordination. In most cases 8p is shifted downfield, but h showed no definite trend. The most effective reagent was cobalt chloride in acetonitrile solution. The H-1 proton of dinucleotide mono- and di-phosphates was identified by the broadening of its resonance that occurred upon the addition of Mn + ions. A study of the effects of paramagnetic ions on adenosine 5 -monophosphate has also been reported.  

A comparison of the calculated and observed n.q.r. resonances has been used to study the stereochemistry and bonding of chloro-compounds such as (105), (106), and (107). The C1 n.q.r. resonances of the thio-phosphoryl chlorides were higher than those of the phosphoryl chlorides. This was attributed to reduced p -d back-bonding from the sulphur 

A similar conclusion was made after a study of the amino-phosphine chalcogenides (108 X = O, S, or Se). It was also found that the occupation number of the nitrogen atom is independent of the phosphorus co-ordination number. The C1 n.q.r. spectra of alkyldichloro-phosphines and their sulphides (109) have been reported.N.q.r. has 

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