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Publication Type
Journal Article
UWI Author(s)
Author, Analytic
Barrett-Adams, Dawn M.Y.,; Kahwa, Ishenkumba A.; Mague, Joel T.; McPherson, Gary L.
Author Affiliation, Ana.
Chemistry; Faculty of Pure and Applied Sciences
Article Title
Preparation, crystal structure and unusual proton NMR characteristics of some phthalimides
Medium Designator
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Connective Phrase
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Journal Title
Journal of Organic Chemistry
Translated Title
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Reprint Status
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Date of Publication
1995
Volume ID
60
Issue ID
18
Page(s)
5946-5953
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ISSN
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Notes
Protection of NH2 groups as phthalimides using a mixture of acetic acid, phthalic anhydride, and the relevant polyamine can take unusual routes. For diethylenetriamine the major product is diphthalimidodiethylammonium-hydrogen phthalate (DPDAH-HP). For triethylemetetraamine, ethylene migration products N, N-bis(2-phthalimidoethyl)piperazine (2) and N,N'N'-(nitrilotri-ethylene) trisphthalimide (3) were obtained from room temperature and refluxing reaction mixtures, respectively. The crystal structures of 2, 3, and DPDAH-HP were determined and revealed a series of stabilizing complementary interactions for these favoured products (i.e., offset p-p stacking and C-H...O and possibly C-H...N hydrogen bonds (2), electrostatic interactions between the amine and pyrrolic functionalities (3), and offset p-p stacking and N-H...O hydrogen bonding (DPDAH-HP)). the DPDAH-HP units stack along a screw axis parallel to the b-direction to yield a striking [phthalimide-phtalimide-hydrogen phthalate]n motif and are linked in the a and c directions by N-H...O bonds. Solution1H NMR studies of 3 reveal unusual temperature (178-420 K) evolution of sharp aromatic proton resonances in various solvents. Typically, the spectra exhibit a spectacular temperature evolution from a sharp doublet of quartets at high temperature to complex second order behaviour and then singlet. As the temperature is further lowered, a complex second order spectrum appears followed by a doublet of quartets. The phthalimide-amine interaction energy, determined from temperature dependent NMR studies, is ca. 20 kJ/mol. Solid state 13C aromatic resonances are broadened by p-p interactions in 2 and DPDAH-HP while two sets of 13C resonances are found for 3 as expected from the solid state structures. The hyrdogen phthalate anion in DPDAH-HP exchanges exhibits almost termperature independent behaviour indicating that it is predominantly etropy driven....
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