Phosphorus dominant groups

The true value of the chloropolymer (I) lies in its use as an intermediate for the synthesis of a wide variety of polytorgano-phosphazenes) as shown in Figure 1. The nature and size of the substituent attached to the phosphorus plays a dominant roll in determining the properties of the polyphosphazene. Homopolymers prepared from I, in which the R groups are the same or, if different, similar in molecular size, tend to be semi-crystalline thermoplastics. If two or more different substituents are introduced, the resulting polymers are generally amorphous elastomers. (See Figure 1.)... 

In the Diels-Alder reaction with inverse electron demand, the overlap of the LUMO of the 1-oxa-l,3-butadiene with the HOMO of the dienophile is dominant. Since the electron-withdrawing group at the oxabutadiene at the 3-position lowers its LUMO dramatically, the cycloaddition as well as the condensation usually take place at room or slightly elevated temperature. There is actually no restriction for the aldehydes. Thus, aromatic, heteroaromatic, saturated aliphatic and unsaturated aliphatic aldehydes may be used. For example, a-oxocarbocylic esters or 1,2-dike-tones for instance have been employed as ketones. Furthermore, 1,3-dicarbonyl compounds cyclic and acyclic substances such as Meldmm s acid, barbituric acid and derivates, coumarins, any type of cycloalkane-1,3-dione, (1-ketoesters, and 1,3-diones as well as their phosphorus, nitrogen and sulfur analogues, can also be ap-... 

Similar observations are possible with acyclic Pv compounds if the substituents of phosphorus are different and also rather bulky (and more especially if chelation can occur to stabilise the conformers).(1969,110) In (CH3)2NP(0)F(C4H9-f), the methyl groups are non-equivalent with 37(P-N-CH3) of 8-2 and 0-0 Hz.(1965,8) The phosphorus inversion remains the dominating phenomenon here. (1969>in>... 

The first two observations indicate that the chiral phosphorus atom in VII dominates over the chiral neomenthyl group in determining the optical yield and absolute configuration of the hydrogenation product. 

The different reactivity of phosphorus azides might be interpreted in terms of conjugation between phenyl groups and sulfur or between phenyl groups and the P=N=0 double bond in these cases the rate of the phenyl migration decreases and hydrogen abstraction reactions dominate. 

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