Physical aspects of N-benzoylaziridine photochemistry. Characterization of azomethine ylides and related photointermediates

Journal Article · Thu Feb 06 04:00:00 EST 1992 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/j100182a046· OSTI ID:379469

Ramaiah, D ^[1]; George, M V; Das, P K ^[2]

---

1. Regional Research Lab., Trivandrum (India)
2. Univ. of Notre Dame, IN (United States); and others

Results of a time-resolved study based on nanosecond laser flash photolysis are presented for phototransients derived from three N-benxoylaziridines in fluid solutions. The major transients, best assigned as azomethine ylides, are characterized by two maxima (380-440 and 560-610 nm) in the absorption spectrum in the visible region and by microsecond lifetimes at room temperature ({tau}{sup Y} = 0.2-31 {mu}s); these are sluggish in their reactivity toward dimethyl acetylenedicarboxylate (k{sub q}{sup Y} {le} 2.10{sup 4} M{sup -1} s{sup -1} in benzene). Relatively short-lived triplets ({tau}{sub T} = 1-90 ns in benzene), quenchable by biphenyl and 2,5-dimethyl-2,4-hexadiene, act as precursors for the ylides. Between trans-1-benzoyl-2,3-diphenylaziridine (1a) and its cis isomer (1b), {tau}{sub T} is considerably shorter for the former (1 ns for 1a vs 40 ns for 1b, on the basis of the assumption that the rate constant for triplet quenching by 2,5-dimethyl-2,4-hexadiene is 2 x 10{sup 9} M{sup -1} s{sup -1} in benzene); this is explainable in terms of efficient intramolecular quenching of the benzamide-type triplet by a {beta}-phenyl group in 1a while this interaction is less favorable in the most stable conformer of 1b (wherein the benzoyl moiety protrudes away from the cis phenyl groups). Steady-state photolysis and product analysis studies have provided evidence for photocleavage of both C-N and C-C bonds of the aziridine ring. 33 refs., 7 figs., 2 tabs.

• Sponsoring Organization: USDOE
• OSTI ID: 379469
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 3 Vol. 96; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ABSORPTION SPECTROSCOPY
CHEMICAL REACTION KINETICS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMISTRY
PHOTOLYSIS
REACTION INTERMEDIATES
TIME RESOLUTION