Flexibility of supposed "rigid" molecules: substituted 2,5-piperazinediones (diketopiperazines).
The relevant results of accurate X-ray analyses of both the trans-and the L-cis-3,6-dimethyl-2,5-piperazinediones (diketopiperazines) are reported. We note that a large variability of conformations for the ring system can be accomplished by coupling small bond-angle deformations with large variations of the internal rotation angles. The experimental molecular models are discussed in terms of these changes and in terms of nonbonded intramolecular interactions.
POLYMER RESEARCH INSTITUTE, POLYTECHNIC INSTITUTE OF BROOKLYN, NEW YORK.
E
E
Benedetti
P
P
Corradini
M
M
Goodman
C
C
Pedone