The kinetics of the reactions of chlorodithioformate esters with azide ions in 70% aqueous acetone

Abstract

. J. Chem. 54,1906Chem. 54, . (1976.The rates of reaction of a series of chlorodithioformate esters with azide ions in 70% aqueous acetone decrease with increasing electron donation to the reaction site. This order is the reverse of that observed for Sxl solvolysis. The entropies of activation are highly negative and the rapid rates of azide attack result from the low activation energies. These results indicate a bimolecular mechanism for azide attack and this is supported by the first-order dependence of the reaction rate on azide concentration. ALAN QUEEN, DAVID M. MCKINNON et ALEXANDER W. BELL. Can. J. Chem. 54.1906. (1976.Les vitesses de rtkction d'une serie d'esters de I'acide chlorodithioformique avec les ions azotures dans I'acCtone aqueux a 70% diminuent avec une augmentation de la densite Clectronique au site de la rCaction. Cet ordre est I'inverse de celui observe pour les rtkctions de solvolyse SN1. Les entropies d'activation sont trks negatives et les vitesses rapides de I'attaque par les ions azotures proviennent d'inergies d'activation faibles. Ces resultats indiquent que les ions azotures attaquent par un mecanisme bimolbulaire et cette conclusion est en accord avec la dependance du premier ordre des vitesses de rtkction sur la concentration des ions azotures.[Traduit par le journal]

Correlations of the Specific Rates of Solvolysis of Aromatic Carbamoyl Chlorides, Chloroformates, Chlorothionoformates, and Chlorodithioformates Revisited

“…With phenyl chlorodithioformate, the correlations support the claim by Queen [ 40 , 45 ] that the solvolyses involve an ionization mechanism. A good correlation is obtained across the full range of 31 solvents with either equation 2 ( R = 0.987) or equation 3 ( R = 0.990).…”

“…Queen also studied the solvolyses of phenyl chlorodithioformate ( Scheme 5 ) and for solvolysis in 70% acetone [ 40 , 45 ] concluded that the mechanism was S N 1 in character. Our investigation [ 42 ] indicated the reaction to be unimolecular across the full range of the 14 solvents utilized ( ℓ = 0.55; m = 0.84) including the solvolysis in 100% ethanol, which would be the most favorable for bimolecular reaction.…”

Influence of Sulfur for Oxygen Substitution in the Solvolytic Reactions of Chloroformate Esters and Related Compounds

“…Addition of azide ion led to reduced amounts of acid production and formation of products from azide attack ( Scheme 5 ). In this scheme [ 82 , 83 ] the azide product, which spontaneously cyclizes, is produced directly by a bimolecular pathway and indirectly by capturing the carbocation produced. Added chloride ion can compete for capture of the carbocation by an external return pathway or the carbocation can be captured by water from the solvent to give a half-ester, which loses COS and gives the methanethiol.…”

“…Added chloride ion can compete for capture of the carbocation by an external return pathway or the carbocation can be captured by water from the solvent to give a half-ester, which loses COS and gives the methanethiol. The kinetics in the presence of a relatively large concentration (0.05 to 0.2 mol/L) of azide ion is first-order in substrate and first-order in azide ion [ 83 ] and the solvolysis reaction observed in its absence is almost totally suppressed.…”

Dual Pathways in the Solvolyses of Phenyl Chlorothioformate

“…A fairly delicate balance between the unimolecular and bimolecular pathways on replacement of the oxygen atoms of PhOCOCl with sulfur atoms was indicated by the observation that, while the hydrolysis in aqueous acetone of chlorodithioformate esters (RSCSCl) had the characteristics of an ionization process (S N 1 mechanism), the addition of azide ion led to a bimolecular attack by the anion …”