NMR of terminal oxygen. 9—¹⁷O NMR of the PO ‘double bond’: Phosphine oxides, phosphinates, phosphonates, acylphosphonates and related compounds

Di(hydroperoxy)cycloalkane Adducts of Triarylphosphine Oxides: A Comprehensive Study Including Solid-State Structures and Association in Solution

“…The δ­( 17 O) of the PO groups of the Ahn adducts 3 – 6 are found within the range of 48.37 to 63.73 ppm (Table ), in accordance with the range for the hydrogen peroxide (Hilliard) adducts of the same phosphine oxides (46.60 to 60.04 ppm), and with other compounds incorporating phosphorus–oxygen double bonds . As compared to the δ­( 17 O) of the PO group of 1 (50.35 ppm; Table ), the chemical shift for the oxygen nucleus of Ph 3 PO in CDCl 3 has been reported as 43.3 ppm …”

Oxygen-17 NMR spectroscopy: Basic principles and applications (Part I)

“…As expected, the terminal P-O groups show lower sensitivity, compared with e.g., carbonyl groups, to structural variations, such as geminal group substitutions (with the exception of Cl and Br), and a very [488]. low sensitivity to arene ring substituents.…”

“…This is much smaller than in methyl benzoates (q + = 8) or acetophenones (q + = 22) [340,349]. It was suggested [488] that in the absence of a free p-orbital on P, back-donation from O to P does not play an important role and, therefore, P + -O À is a more appropriate resonance structure [489,490]. Due to tetrahedral configuration at P, resonance interactions between P@O and electron donors X in P(O)X are minor, contrary to the case of the planar carbonyl groups.…”

McKenna Reaction—Which Oxygen Attacks Bromotrimethylsilane?

“…Readily available diethyl phenylphosphonate ( 11 ) was selected as a model compound, since it is a typical representative of phosphonates, the most abundantly studied class of organophosphorus esters. 17 O-enriched 11c and its bis(trimethylsilyl) analogue 12c have been fully characterized previously by 17 O NMR spectroscopy, with the chemical shifts of both the bridging and terminal oxygens being determined . Such data make this ester an ideal reference compound for the studies presented here.…”

“…Still, 17 O NMR analysis of P–O-containing compounds is appropriate for probing their structure, bonding, and dynamics and is a valuable tool in some stereochemical analyses on the basis of their peak shapes (usually a well-resolved doublet for the PO oxygen vs a broad peak for the P–O–R oxygen) or chemical shifts . Application of 17 O NMR in titration studies showed that protonation of the phosphonate oxygen is accompanied by an upfield shift ∼50 ppm per charge neutralized …”