Characterization of Secondary and Primary (Hydroxymethyl)Phosphines and Their Oxidation Products: Synergism in Pulp-Bleaching

Abstract

With the aim of learning about the synergistic effect of a combination of (HOCH₂)₃P and Na₂S₂O₄ for the bleaching of mechanical pulps, reactions of (HOCH₂)₃P (and its associated precursor, (HOCH₂)₄P⁺Cl⁻) with Na₂S₂O₄ were studied in aqueous media under Ar and in air. The secondary phosphine (HOCH₂)₂PH is the major product in a 1:1 reaction of (HOCH₂)₃P and Na₂S₂O₄ under Ar, the formaldehyde being removed in the form of HOCH₂SO₃Na and HOCH₂SO₂Na; the latter is Rongalite, itself an industrial bleaching agent. Significant amounts of the primary phosphine HOCH₂PH₂ are also seen. When the reaction is performed in air, the oxide (HOCH₂)₂P(O)H is the main product. Reaction of (HOCH₂)₄P⁺Cl⁻ with Na₂S₂O₄ (even under Ar) leads to solely the oxidation products: (HOCH₂)₃PO, (HOCH₂)₃PS, and (HOCH₂)₂P(O)OH. ³¹P{¹H} and ¹H NMR spectral data for secondary and primary (hydroxymethyl)phosphines and their oxidation products are reported for the first time. The toxicity of the primary and secondary phosphines is likely to curtail their use in commercial bleaching processes.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

GRAPHICAL ABSTRACT

Keywords:

• (Hydroxymethyl)phosphines
• secondary phosphines
• primary phosphines
• dithionite
• hydrosulfite
• pulp bleaching
• synergic effect

Acknowledgments

We thank the Natural Science and Engineering Council of Canada for financial support via a Discovery Grant and an Idea to Innovation (I2I) Phase 1 Grant.