Multinuclear NMR Studies and Spin System Analyses on Dibenzo[c.e][1,2]Oxaphosphorine 2‐Oxides

Abstract

2H‐Dibenzo[c.e][1,2]oxaphosphorine 2‐oxide (HDOPO), 2‐(N,N‐diethylamino)‐dibenzo[c.e][1,2]oxaphosphorine 2‐oxide (DEADOPO), and 2‐ethoxy‐dibenzo[c.e][1,2]oxaphosphorine 2‐oxide (EtODOPO) are fully characterized in CDCl3 by 1H, 13C, 31P, and 15N NMR spectroscopy on 800‐ and 500‐MHz instruments. A strategy enabling their unambiguous signal assignment is presented, with special emphasis on 2D 1H,13C HMBC spectra. Additional line‐shape iterations of the aromatic 1H multiplets (ABCDX and ABCDEX spin systems) provided all long‐range nJH,H and nJP,H coupling constants with utmost precision. The experimental results augmented with those of the model compound phenylphosphonous acid clearly demonstrate that nJH,H couplings of the PH proton as well as the nJP,C values do not decrease in a monotonic manner with the number of intervening bonds from the phosphorus atom. This fact may potentially lead signal misassignments, if the analysis starts out from the coupling constants, as it occurred for HDOPO in the recent publication by Wagner et al. (Phosphorus, Sulfur and Silicon, 187, 2012, 781–798). The corrected assignment will be given in the present paper. Finally, the A2M3X or ABM3X type 1H spectral patterns of ethyl groups are also analyzed and explicit equations are derived to evaluate the strongly coupled ABM3X multiplets in EtODOPO.

Comparative study of reactive flame retardants based on 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide

“…10-Chloro-10H-9-oxa-10-phospha-phenanthrene was synthesized according to a method published elsewhere. 11 DOPO-H (742.17 g, 3.4 mol) was suspended in chloroform or xylene and to this suspension was added PCl 3 (565.7 g, 4.1 mol) under a nitrogen atmosphere. A homogenous solution was observed after 15 min stirring at room temperature.…”

“…DOP-OEt [1192-20] was synthesized according to a procedure reported in the literature. 11 DOP-Cl (741 g, 3.1 mol) was dissolved in anhydrous xylene (400 mL) to obtain a homogenous solution. To this solution was added triethylamine (353 g, 3.5 mol) under a nitrogen atmosphere.…”