Saber M. Sharaf

Kinetics of the reaction of 2‐chloro‐3,5‐dinitropyridine with meta‐ and para‐substituted anilines in methanol

The kinetics of the reaction of 2-chloro-3,5-dinitropyridine (1) with meta- and para-substituted anilines (2a–j) to give 2-anilino-3,5-dinitropyridine derivatives (3a–j) were studied in methanol at different temperatures. IR studies of the products (3a–j) indicated the presence of hydrogen bonding between N—H and an o-nitro group, and UV spectra showed a red shift resulting from the interaction between an amino group and aza and nitro groups. A plot of ΔH‡ versus ΔS‡ gave a good straight line with a 324 °C isokinetic temperature. Good linear relationships were obtained from plots of log k2 against σ values at all temperatures with relatively large negative ρ values (−3.75 to −3.16) indicating the formation of a Meisenheimer σ-complex intermediate. Plots of log k2 against pKa values (β = 0.85) gave good straight lines at 25 °C, except for 2f (4-COCH3), indicating that the reactions involve a significant bond formation in the transition state. An SNAr mechanism is suggested to proceed via two stages, with the first being rate determining. Copyright

Mass spectrometric study of some pyrazoline derivatives

The structures of some new carboxamide, thiocarboxamide, nicotinoyl and isonicotinoyl pyrazoline derivatives have been related to their mass spectral data. The ions produced under electron impact showed both the characteristic pyrazoline ion and unusual azete fragmentation patterns. These results suggest that the mass spectra of these pyrazoline derivatives are both position and substituent dependent. Fragmentations of the ions are discussed in view of their metastable transitions.

Studies on aroyl- and aryl-hydrazide derivatives from d-glycero-d-gulo-heptono-1,4-lactone

Abstract A series of aroyl- and aryl-hydrazide derivatives was prepared from d - glycero - d - gulo -heptono-1,4-lactone ( 1 ). The reactivity of the NH proton in these hydrazides, in terms of their dissociation constants (p K a ), was determined from their electronic spectra, and correlated to the Hammett σ values of the substituents. Comparable reactivities of the NH protons for the compounds, and the effect of the substituent, were studied by n.m.r. spectroscopy. Decomposition of the aroylhydrazides with copper(II) sulfate or nitrous acid resulted in the regeneration of 1 .