The reaction of propargyl chloride with As(III) and S(IV) nucleophiles

Abstract

Propargyl chloride, CH≡C–CH₂Cl, was virtually inert towards NaH₂AsO₃, reacted to a very small extent with Na₂HAsO₃, but with Na₃AsO₃ gave a mixture of salts in which sodium 1-propynylarsonate, CH₃–C≡C–AsO₃Na₂ 6, predominated, the allenylarsonate, CH₂ = C = CH–AsO₃Na₂ 4, being present in (very) small amounts, while the isomeric 2-propynylarsonate CH≡C–CH₂–AsO₃Na₂ 5 was not detected. These results can be understood by attack of AsO₃^3– on propargyl chloride to form 5 followed by base catalyzed prototropic rearrangements to 4 and to 6. Separation of 6 from 4 was tried as acids or salts without success. The purity of the product as acid 6 and lead salt of 6 was >80%. The reaction of propargyl chloride with Na₂SO₃ required dilute aqueous solutions (∼0.3 M) in order to give the salt CH≡C–CH₂–SO₃Na·4H₂O, 11·4H₂O, in ∼80% yields. More concentrated solutions (1 or 2 M) produced 11 and by-products from which CH₂ = C = CH-SO₃Na 10, but not CH₃–C≡C–SO₃Na 12, has been identified spectroscopically, while potassium 2-chloro-2-propenylsulfonate tetrahydrate CH₂ = CCl–CH₂–SO₃K·4H₂O, 13·4H₂O, was isolated.