Durch Anlagerung der Triaminophosphite (I) an N‐acetylierte Aminoalkohole (IIb) und (IIc) bzw,N‐Acetyl‐o‐aminophenol (IIa) entstehen die 2‐Diäthylt amino‐3‐acetyl‐l ,3,2‐oxazaphospholane (IIIa) und (IIIb) bzw. Oxazaphosphorinane (IIIc).
The partial molar volumes (V) and the enthalpies of dissolution (Adis/'~ for tetracyanoethylene, cyclopentadiene, and their Diels--Atder adduct were determined at 25 ~ Eleven solvents of the ~-and n-donor type were used. The use of alkylbenzenes as solvents t'or tetracyanoethylene induces pronounced changes in the enthalpy of dissolution (up to 26 kJ tool -l) and in the partial molar volume (up to I I cm 3 tool-I), whereas these parameters for the adduct change slightly. The V and ,5,jisH values for cyclopentadiene virtually do not depend on the nature of the solvent. In the case of tetracyanoethylene and the adduct in n-donor solvents, considerable variations of the Vand AdisH values are observed; they are not linear functions of the change in the partial molar volume of the adduct. Theretbre, the reaction volumes in acetonitrile (-40.69) and ethyl acetate (-45.56) differ sharply from those in o-xylene (-24.28) and mesitylene (-21.76 cm 3 mot-I).Key words: partial molar volume, reaction volume, tetrzcyanoethyIene, specific interactions, Oiels--Alder reaction.The use of elevated pressures provides data on the activation and reaction volumes of chemical reactions and allows more precise elucidation of the nature of the activated complex and its location on the reaction coordinate. I-5 A recent study is devoted to the reversible Diels--Alder reaction between tetracyanoethylene and 9-chloroanthracene. 6 It was found that the reaction volumes determined by indirect methods (from the difference between the activation volumes of the forward and reverse processes and from the pressure dependence of the equilibrium constant) and by the direct method (from the difference between the partial molar volumes of the adduct and the reagents) are equal within the accuracy of determination. For polar and ionic processes, the contribution of the solvent electrostriction effect to the overall activation volume can be commensurable with and even exceed in magnitude the structural contribution. 7 A more accurate estimation of the contribution of solvent electrostriction in the solvation of a polar or ionic activation complex requires consideration of the influence of the variable properties of the medium on the reaction rate at elevated pre~ure, a An influence of the solvent on the activation volume has been established for many processes accompanied by the formation of polar or ionic states. I-9 Testing of the process using the data on the influence of lithium perchlorate in diethyl ether on the cycloaddition rate showed that the activation complex in the Diels--Alder reaction involving tetracyanoethylene should be relatively nonpolar. 1~ This means that solvent electrostriction in the solvation shell of the activated complex should be insignificant, in this work, we studied the reaction of tetracyanoethylene with cyclopentadiene in different solvents of the rt-and n-donor type (Scheme I). Tetracyanoethylene is a strong n-acceptor (electron affinity 2.88 eVil); however, its rc-acceptor properties should not be manifested in full mea...
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