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NUCLEOPHILIC AROMATIC-SUBSTITUTION IN HETEROCYCLES - ALCOHOLYSIS AND HYDROLYSIS OF 2-ANILINO-4,6-DICHLORO-1,3,5-TRIAZINES

Renfrew, A. Hunter M., Taylor, John A., Whitmore, James M.J., Williams, Andrew (1994) NUCLEOPHILIC AROMATIC-SUBSTITUTION IN HETEROCYCLES - ALCOHOLYSIS AND HYDROLYSIS OF 2-ANILINO-4,6-DICHLORO-1,3,5-TRIAZINES. Journal of the Chemical Society-Perkin Transactions 2, (12). pp. 2389-2393. ISSN 0300-9580. (doi:10.1039/P29940002389) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:19984)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided.
Official URL:
http://dx.doi.org/10.1039/P29940002389

Abstract

Kinetics are reported for the alkaline hydrolysis of 2-anilino-4,6-dichloro-1,3,5-triazines to yield the corresponding mono-hydroxy species. The pseudo-first-order rate constants are independent of general-base concentration and obey the rate law eqn. (i), where K-1 = K-w/K-a, K(a)is the ionisation (i) k(obs) = (k(H2O) + k(OH)K(1)[OH])/([OH] + K-1) constant for the aniline proton and k(OH) is the bimolecular rate constant for attack of hydroxide ion on the neutral triazine molecule. The parameters k(OH) and K-a obey Hammett equations with sigma degrees[eqns. (ii) and (iii)]. The kinetically determined pK(a) of the 4-chloroanilino-4,6-dichloro-1,3,5- (ii) log k(OH) = 1.06 +/- 0.15 sigma degrees - 0.064 +/- 0.054 (r = 0.9709) (iii) pK(a) = -2.13 +/- 0.16 sigma degrees + 10.92 +/- 0.06 (r = 0.9919) triazine is close to that measured by pH-titration. The kinetics for hydrolysis and alcoholysis of 2- (N-methyanilino)-4,6-dichloro-1,3,5-triazine are independent of general-base concentration and are first order in oxyanion and triazine concentration; the derived second-order rate constants (k(RO).) (excepting the hydroxide term) obey the extended Bronsted equation (iv). (iv) log k(RO) = 0.84 +/- 0.06 pK(a)(ROH) - 10.89 +/- 0.87 (r = 0.9886) The hydroxide ion term is some three orders of magnitude less nucleophilic than an alkoxide of the same pK(a). The data exclude the conjugate base of the 2-anilino-4,6-dichloro-1.3.5-triazine as a major contributor to the reaction flux of the hydrolysis and are consistent with a mechanism involving addition of the hydroxide ion to the neutral triazine. The polar substituent effects on the hydroxide ion reactivity indicate that there is substantial charge accumulation in the triazine nucleus in the transition state of the addition step.

Item Type: Article
DOI/Identification number: 10.1039/P29940002389
Subjects: Q Science > QD Chemistry
Divisions: Divisions > Division of Computing, Engineering and Mathematical Sciences > School of Engineering and Digital Arts
Depositing User: P. Ogbuji
Date Deposited: 19 Jun 2009 17:03 UTC
Last Modified: 16 Nov 2021 09:58 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/19984 (The current URI for this page, for reference purposes)

University of Kent Author Information

Williams, Andrew.

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