Monocyclic azines nucleophilic substitution

Kinetic Data on Nucleophilic Substitution of Monocyclic Azines... 

In bicyclic azines, as in the monocyclic azines already discussed, the faster of two nucleophilic substitutions proceeds via the transition state which has the lower free energy (with respect to the reactants) due to the stabilizing effects of resonance, hydrogen bonding, or electrostatic attractions. Different nucleophiles and different leaving... 

Chlorophthalazine is quite reactive to many basic nucleophiles but reacts sluggishly with aqueous or alcoholic alkali. In contrast, it is very rapidly hydrolyzed by warm, concentrated hydrochloric acid as are its diazine isomers. In hydrolysis with very dilute acid or with water, it forms some phthalazinone but mostly the self-con-densation product which hydrolyses to give 2-(l -phthalazinyl)-phthalazin-l-one (70% yield). Such self-condensations in diazanaph-thalenes and in monocyclic azines are always acid-catalyzed (Sections II, C and III,B). With methanolic methoxide, 1-chlorophthalazine (65°, few mins), its 7-methoxy analog (20°), and 1,6- and 1,7-dichlorophthalazines (20°) readily undergo mono-substitution. 

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