Hydrogen Bonding: HOC=O· · ·H-N vs. HOC=O· · ·H-C.
A chloroform-soluble dipyrrinone, 8,9-bis-(5-carboxypentyl)-2,3-bis-(2-methoxyethoxy)-10H-dipyrrin-1-one, with solubilizing 2-methoxyethoxy β-substituents on the lactam ring and two hexanoic acid groups (one at C(9), the other at C(8) of the pyrrole ring) was synthesized for its ability to form intramolecular hydrogen bonds to the lactam unit from either carboxylic acid, whether in thesyn-(Z) oranti-(Z) conformation. In thesyn-(Z) conformation, such intramolecular hydrogen bonds can also include the pyrrole N-H. In theanti-(Z), intramolecular hydrogen bonds can include the pyrrole C(7)-H. Evidence for both monomer conformations in equilibrium is provided by1H NMR analyses, which indicate that thesyn-(Z) is favored over theanti-(Z) and predict an interconversion barrier of approximately 40 kJ mol-1.
Milliken & Company, PO Box 1926, Spartanburg, SC 29304.
Sanjeev K
SK
Dey
Milliken & Company, PO Box 1926, Spartanburg, SC 29304.
Suchitra
S
Datta
Department of Chemistry, University of Nevada, Reno, Nevada, 89557-0216 USA.
David A
DA
Lightner
Conformation; NMR; Pyrroles