Nitrogen-bonded σ-adducts from amide anions and 1,3,5-trinitrobenzene. A 1H nuclear magnetic resonance structural study

Abstract

The reactions of several amide and imide anions with 1,3,5-trinitrobenzene (TNB) have been studied in acetonitrile and dimethyl sulphoxide. U.v.–visible and ¹H n.m.r. spectra have allowed complete characterization of the N-adducts but the formation of the isomeric O-adducts was not observed. Some N-adducts are found to exist as a mixture of Z and E isomers. In these instances the preferred isomer adopts the E configuration in which the bulky TNB substituent is trans to the carbonyl oxygen. Probable conformations around the N–C_sp³ bond of the adducts are discussed in the light of the values of the ³J_HNCH coupling constant. Most N-adducts have a thermodynamic stability which is of the same order as that of the TNB–methoxide adducts. This results as well as the failure to observe the O-adducts is shown to be consistent with literature data.