Aggregation of Phosphoric Acid, Phenyl Dihydrogenphosphate, and Related Organophosphorus Acids in Conductometric Titration with Triethylamine in DMF.

• Hojo Masashi

  Department of Chemistry, Faculty of Science, Kochi University

• Hasegawa Hiroshi

  Department of Chemistry, Faculty of Science, Kochi University

• Chen Zhidong

  Department of Chemistry, Faculty of Science, Kochi University

Bibliographic Information

Other Title

• Aggregation of Phosphoric Acid Phenyl D

Abstract

The conductance increased linearly up to the equivalence point in the conductometric titration of diphenyl hydrogenphosphate ((PhO)₂PO(OH)) with triethylamine (Et₃N) in DMF at 25 °C. However, it was found that the conductometric titration of phenyl dihydrogenphosphate (PhOPO(OH)₂, 1.0 × 10⁻³—1.0 × 10⁻² mol dm⁻³) gave a maximum at the half-equivalence point (C_HA : [Et₃N] = 1 : 1/2) and not the linear curve to the equivalence point. Phosphoric (PO(OH)₃), phenylphosphonic (PhPO(OH)₂), and vinylphosphonic (CH₂CHPO(OH)₂) acids also gave maxima at the half-equivalence points. The appearance of maxima was explained by homoconjugation between the acid (HA) and the conjugate anion (A⁻) upon neutralization with the base (B) in DMF : B + 2 HA BH⁺···HA₂⁻. Dibutyl hydrogenphosphate ((n-BuO)₂PO(OH)) of higher concentrations also gave a (small) maximum at the half-equivalence point, while dimethylphosphinic acid ((CH₃)₂PO(OH)) gave no maximum in DMF. In less basic solvents, acetonitrile and benzonitrile, even diphenyl hydrogenphosphate, gave a maximum. The cause for the appearance of maxima at the half-equivalence point in DMF is discussed from the viewpoint of the basicities of the conjugate anion (A⁻) and the number of hydrogen bondings involved in the homoconjugation reaction. The ion-pair and quadrupole (the dimer of ion pairs) formation constants of the organophosphorus acids in DMF were obtained by conductometry. The equilibrium concentration of the dimer (H₂A₂) of PhOPO(OH)₂ was found to exceed that of the ion pair (HA) at >1.6 × 10⁻³ mol dm⁻³ of the acid.

Journal

• Bulletin of the Chemical Society of Japan

  Bulletin of the Chemical Society of Japan 69 (8), 2215-2220, 1996

  The Chemical Society of Japan

Keywords

• General Chemistry

Details

• CRID: 1390282679098417408
• NII Article ID: 130004057987
• NII Article ID: 10008906992
• NII Book ID: AA00580132
• DOI: 10.1246/bcsj.69.2215
• COI: 1:CAS:528:DyaK28Xlt1yrsrc%3D
• ISSN: 13480634
• ISSN: 00092673
• ISSN: http://id.crossref.org/issn/00092673
• NDL BIB ID: 4060539
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I4060539
• Web Site: https://academic.oup.com/bcsj/article-pdf/69/8/2215/56196403/bcsj.69.2215.pdf
• Text Lang: en
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed