五酸化リン

Phosphorus pentoxide can be prepared by reacting phosphorus with air. It is commonly used as a dehydrating and condensing agent in organic synthesis.

Phosphorus pentoxide may be used for the vacuum distillation of 1-methyl-2-pyrrolidinone (NMP), which was employed as mobile phase in a chromatographic analysis.
It may be used as one of the reaction components in the synthesis of dichlorine heptoxide (Cl₂O₇) and transition-metal phosphides (Ni₂P, Co₂P and MoP). P₂O₅ supported on alumina can be used for the solvent-free and microwave-assisted preparation of 1, 5-benzodiazepine analogs. P₂O₅/KX (X = Br, I) reagent system may be used for the transformation of alcohols into the corresponding alkyl iodides and bromides.

Phosphorus pentoxide/methanesulfonic acid (PPMA) may be used as a condensing agent and solvent for the synthesis of:

• High molecular weight poly(benzoxazole)s via direct polycondensation of aromatic dicarboxylic acids containing phenyl ether structure with 3,3′-dihydroxybenzidine dihydrochloride.
• Aromatic poly(phenylene ether ether ketone)s via direct self-polycondensation of 4-(4′-phenoxyphenoxy)benzoic acids.P8}
• 1,3-1H-dibenzimidazole-benzene by the reaction of isophthalic acid with 1,2-diaminobenzene.