2- -s-triazine

It has already been mentioned that the degradation of s-triazine herbicides such as atrazinc in soil can be described by two reaction types only, hydrolysis and reductive dealkylation (see Figure 10.3-8). Application oF these two reaction types to a specific s-triazinc compound such as atrazinc provides the reaction network shown in Figure 10,3-12. This can also be vcriFicd by running this example on h ttp //www2,chemie,uni-erlangen.de/semces/eros/,... 

Figure 10.3-13. s-Triazine herbicides and their half-life ill soil [16],... 

The removal of the two alkyl groups comprises the two primai y steps, the abstraction of the ethyl group being the dominant one. These products show up first, as can be seen on the left-hand side of Figure 10.3-14, It can also be seen that it is expected that after one year an apprceiable amount of s-triazine eom-pounds will still be found in the soil. 

Formamidinoyl isothiocyanates (157) combine with 2-aminothiazoles the ring nitrogen attacks the spC part of the electrophilic reagent (312) further reaction then yields aza-condensed thiazolo-s-triazines (158) (Scheme 99) (313). Mesoionic S-alkvlthiazolo[3.2-fl]-i-tria2ine-5,7-diones (159) are obtained when 2-alkylaminothiazoles react with phenoxycar-bonyl isocyanate (304). 

Heating of this latter compound with an excess of phenyl isothiocyanate in acetonitrile (65) leads to 2-phenylimino-3-phenyl-4-thioxo-se enazole[3.2-a]tetrahydro-s-triazin (Scheme 61). 

Similarly, the reaction of carbethoxyisothiocyanate (EtO CNCSl with 2-aminoselenazo ine leads to 2.3,6.7-tetrahydro-4H-selenazoio[3.2-fl]-s-triazin-2-one-4-thione Scheme 62 (66). 

Tris(4-tert-butyl-3-hydroxy-2,6-dimethylben2yl)s-triazine-2,4,6-(lH,3H,5IT)trione [40601-76-1]... 

An unusual reaction involving s-triazine (247) and ethyl acetoacetate with sodium ethoxide leads eventually to the pyrido[4,3-ring opening and Dimroth-type rearrangement of the intermediate (248) (80JHC389>. 

Amino-4-anilino-s-triazine [537-17-7] M 168.2, m 235-236 , pKsst-5.5. Crystd from dioxane or 50% aqueous EtOH. 

Chemical Designations - Synonyms 2-Chloro-4-Ethylamino-6-Isopropylamino-S-Triazine, Aatrex Herbicide Chemical Formula C8Hi4NjCl. 

Chemical Designations - Synonyms Trichloroiminoisocyanuris acid Trichloroisocyanuric acid Trichloro-s-Triazine-2,4,6-(lH,3H,5H)-trion Trichlorotriazinetrion 1,3,5- Trichloro- 2,4,6-trioxo-1,3,5-triazine Chemical Formula Cl3(NCO)3. 

According to the triazine nomenclature, 5-azauracil is 2,4-dioxo-l,2,3,4-tetrahydro-l,3,5-triazine (2). The subject index of Chemical Abstracts prefers s-triazine-2,4(lH,3H)-dione. Furthermore, some authors use a name derived from the lactim structure, 2,4-dihydroxy-s-triazine (3). The numbering of the substituents is the same for all these types of nomenclature. 

Other derivatives of s-triazine, in particular the 2,4-disubstituted ones, are usually prepared by total synthesis and are therefore not closely linked with the chemistry of 5-azauracil unlike the analogous derivatives of 1,2,4-triazine. 2,4-Dimethoxy-l,3,5-triazine was mentioned earlier (e.g., Section II,A,2,a), the other substances are not related to the present subject. 

In connection with the biological activity of s-triazines, Burchfield and Storrs investigated the reaction of 2,4-dichloro-6-(o-chloro-anilino)-s-triazine with over sixty amino acids, peptides, and related... 

Goi. As noted previously, an a-chlorine atom renders a ring-nitrogen atom very weakly basic. Cyanuric chloride (5) is a very weak base both because s-triazines are of low basicity and because each of the ring-nitrogen atoms is alpha to two chlorine atoms. Hence, this compound should be insensitive to acid catalysis or acid autocatalysis and this has been observed for the displacement of the first chlorine atom with alcohols in alcohol-acetone solution and with water (see, however. Section II,D,2,6). 

In this solvent the reaction is catalyzed by small amounts of trimethyl-amine and especially pyridine (cf. 9). The same effect occurs in the reaction of iV -methylaniline with 2-iV -methylanilino-4,6-dichloro-s-triazine. In benzene solution, the amine hydrochloride is so insoluble that the reaction could be followed by recovery. of the salt. However, this precluded study mider Bitter and Zollinger s conditions of catalysis by strong mineral acids in the sense of Banks (acid-base pre-equilibrium in solution). Instead, a new catalytic effect was revealed when the influence of organic acids was tested. This was assumed to depend on the bifunctional character of these catalysts, which act as both a proton donor and an acceptor in the transition state. In striking agreement with this conclusion, a-pyridone is very reactive and o-nitrophenol is not. Furthermore, since neither y-pyridone nor -nitrophenol are active, the structure of the catalyst must meet the conformational requirements for a cyclic transition state. Probably a concerted process involving structure 10 in the rate-determining step... 

Reagent P-K a 2-Chloro- pyrimidine 2-Chloro- 3-nitro- pyridine 2-Chloro- 5-nitro- pyridine 2,4-Dichloro- phenylamino-s-triazine ... 

The reaction of anilines (R = H, m- and p-CHg, p-OCHg, p-Cl) with 2-chloro-4,6-diphenoxy-s-triazine. ... 

The high reactivity of trichloro-s-triazine and tetrachloropyrimi-dine, the ease of replacement of the first chlorine atom from these compounds with several types of nucleophiles (amines, alcohols, etc.) and, finally, the important role of these reactions in dye chemistry have stimulated many investigations dealing with substituents of the general types RZ and R2Z, where Z is an electron-donor atom or group (NH, 0, S, N). 

Data by Matsui et and Goi for the reactions of chloro-s-triazine derivatives of series 51 and 52 are assembled in Table XIV. 

Effect of Some Nitrogen-, Oxygen-, and Sulfur-Containing Groups on the Rate Constants for the Reaction of Chloro-s-triazine Derivatives with Various Nucleophiles... 

Series 2-amino-4,6-dichloro-s-triazine k in liter x mole i x min i. Ref. 27. 

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