
%0 Journal Article
%A Radom, L 
%A Riggs, NV 
%T <I>Ab initio</I> studies on amides: triformamide
%J Australian Journal of Chemistry
%D 1981/01/01
%V 34
%N 1
%P 7-11
%K 
%R https://doi.org/10.1071/CH9810007
%U https://www.publish.csiro.au/paper/CH9810007 
%X Complete optimization with the STO-3G basis set of the geometries of the planar ground-state conformers of the (unknown) triformamide molecule predicts that the E,E,E conformer will be more stable than the E,Z,Z conformer by 12.6 kJ mol-1 (or 42.3 kJ mol-1 by energy evaluations with the 4-31G basis set). These differences make direct observation of the E,Z,Z-conformer unlikely. Corresponding optimization of a model transition state for the conversion of the E,Z,Z into the E,E,E conformer suggests that the barrier to internal rotation is low with a calculated height of 33 kJ mol-1 (24 kJ mol-1 when evaluated with the 4-31G basis set). Successive formyl substitution in ammonia, represented by the series of molecules formamide, diformamide (formimide) and triformamide, leads to decreasing double-bond character in the N-C bonds as reflected in increasing N-C bond lengths, decreasing Mulliken &#960;-overlap populations and decreasing barriers to rotation. Extension of the results for these three molecules suggests that the (known) triacetamide molecule has a non-planar E,E,E-type structure as is consistent with the observation of a single signal in its 1H n.m.r. spectrum. 
