Triazine cation

Figure 4.4 Structure of the tris[2-(oxoethyl-jV-2 -fluoroethylimidazolium)]triazine cation...

Due to their ionic interaction, they conquer the dipole attraction and in fact, ionic dipolar compounds exhibit excellent bulk SHG efficiency [7-10]. Dynamic hyperpolarizabiUties of 1,3,5 substituted benzenes and triazines cations calculated by ZINDO/CV/SCRF method are listed in Table 6. Experimental data [92] for the corresponding neutral octupolar molecules (as shown in Figure 15) are also listed in Table 6. 

When excess acid is added to the system, H ions (actually hydro-nium ions) compete for adsorption sites (Equation 6) and displace the pesticide cations back into solution as shown in Figure 9 where the pH decreases from 4 to 1 for prometone. Again the process depends upon the pKa of the compound for example, propazine cations are not released until the pH decreases from 2 to 1 (Figure 9). When strongly acid exchange resins were used, the s-triazine cations released were in the hydroxy form, having been hydrolyzed at the resin surfaces (57). 

To discuss these arguments we will have a look at the structures of the transition states for the three mechanisms previously proposed. Mechanism 1 involves two steps and in consequence two transition states (10 and 11) should be considered, but none of them is particularly crowded. The first 10, involves the C2-C1 bond breaking of triazine 5 (dissociative process) leading to triazine cation 7. The amine is involved in the second step, consisting on the formation of a new bond between an unsubstituted position of the triazine ring (C2) and the morpholine nitrogen atom (Scheme 26.6). 

Pyrido[2,l-/][l,2,4]triazine-5,6,7,8-tetracarboxylic acid, 4,4a-biphenyl-l-p-tolyl-synthesis, 3, 428 Pyridotropylium cations... 

Another nucleophilic substitution demonstrating greater reactivity at the 5-position is nucleophihc thionation (via cationized forms of polythiophosphoryloxy intermediates such as structure 126) of as-triazine-3,5-dione and of its 2-methyP and 6-methyl derivatives to form 312 in 50-100% yields. Thionation at the 3-position... 

The effects of the following on nucleophilic substitution of s-triazines are discussed elsewhere hydrogen bonding and cationization (Sections II, C and III, A, 2), the leaving group (Section II, D), other nuclear substituents (Section II, E), and the nucleophile (Section II, F). 

The reaction of 1,2,4-triazine 4-oxides 55 with water in the presence of benzoyl chloride affords 3-hydroxy-1,2,4-triazines 78. The mechanism suggested for this reaction includes acylation of the substrate at the oxygen of the iV-oxide group, followed by the addition of water to the 1,2,4-tiiazinium cation and the autoaromatization of the (T -adducts with the elimination of benzoic acid. 

The recommended field application rates for terrestrial weed control usually range between 0.28 and 1.12 kg paraquat cation/ha (0.25 and 1.0 pounds/acre), between 0.56 and 2.24 kg paraquat dichloride/ha (0.5 and 2.0 pounds/acre) — both applied as an aerosol — and between 0.1 and 2.0 mg/L for aquatic weed control, although sensitive aquatic plants may be affected between 0.019 and 0.372 mg/L (Ross etal. 1979 Summers 1980 Bauer 1983 Dial and Bauer 1984). Paraquat is frequently used in combination with other herbicides (Fletcher 1974 Summers 1980). Water solutions of the dichloride salt, which usually contain 240 g/L, have been successfully mixed with 2,4-D, substituted ureas, dalapon, amitrol, and various triazines (Anonymous 1963, 1974). 

The structures of several compounds containing the pyrrolo[l,2,4]triazine moiety have been established by X-ray crystallography, as for example pyrrolo[l,2- ][l,2,4]triazine 13 <1997J(P1)1829>, 4-acetyl-l-phenyl-2a,3,5-triaza-benz[r-,<7]azulene 14 <2000H(53)323>, heterodiquinane 15 <1998CL1135>, cation 16 derived from methylation of 3-phenylcyclohepta[4,5]pyrrolo[l,2- ][l,3,5]triazine-2,4(377)-dione <2005H(65)1629>, 2-phenyl-3-phenyl-... 

Formation of some mesoionic [ 1,3,4]rhiazolo[3,2-z/ [1,3,5]triazines 303 and related [l,2,4]triazolo[2,3- ][l,3,5]tri-azines 305 has been observed by Anders et al. <2005T673>, as shown in Scheme 60. These authors reported that the quaternary salts 302 and 304 containing polyfused delocalized cations easily react with amines to result in ring opening to 303 and 305, respectively. 

The novel cationic reactant 2,4 dichloro-6 (2, pyridinoethylamino) S triazine (7.128) was evaluated as a means of activating cellulose by pad-batch application at pH 8.5 for 24 hours. This agent contains two reactive chlorine atoms but under these mild conditions only... 

Atrazlne. Atrazine is a chlorinated, a-triazine herhicide. Its water solubility is 33 npm (18), its vapor pressure is 3 X 10 torr (19), and H < 10 atm-i /mole. The pK of atrazlne is 1.68 (40). Kqp values of 51 and 214 have been reported (19,20) and the mean of 56 soils was reported to be 163+80 (41). The Kjj of atrazlne varies between 1 and 8 in certain soils, and seems to be dependent on the cations present (42). Kj values of 0.40-0.46 were also recently reported for aquifer sands in Nebraska (43). Atrazlne is in Helling s mobility class 3, which is the intermediate mobility class (10). (Class 5 is the most mobile, and class 1 is immobile.)... 

The respective association constants of the latter anion to free 376 is only 10 M 1 while for the self-assembled complex it is equal to 2.5 104 M 1 [39]. Kubik and Goddard obtained a cyclic pseudopeptide ditopic receptor 378 for the simultaneous complexation of cations and anions [40]. Simultaneous encapsulation of N03 and PF6 ions by a highly charged (+12) anion receptor 379 was achieved by Schnebeck and coworkers [41]. By coordinating of 2,4,6-tris[(4-pyridyl)methylsulfa nyl]-l,3,5-triazine 380 with Ag, Hong and coworkers obtained nanosized tubes (Fig.7.8.1) that could host solvent and anionic molecules [42]. 

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