We have studied the temperature dependence of the 1 H NMR spectra of some 2,4,6-trisubstituted 1,3,5-triazines having an NHAlk or NAlk 2 group or groups at the position 2 or 2 and 4 of the heterocycle. We have shown that rotation of these groups about the C-N bond is hindered. We have calculated the free energies of activation for the rotation processes.Keywords: 2,4,6-trisubstituted 1,3,5-triazines, hindered internal rotation, isomers, free energy of activation.In the 1 H NMR spectra of triazine derivatives containing NHAlk or NAlk 2 substituents at the positions 2 and 4 of the heterocycle, we observed two or more sets of signals from protons of the N-alkyl and NH groups which may be connected with the presence in the solutions of different isomeric forms of the indicated compounds [1]. In order to study this question, we recorded the 1 H NMR spectra of trisubstituted triazines 1-3 in the temperature range 20-90°C. 1 a R 1 = R 2 = NMe 2 , R 3 = Cl; b R 1 = NMe 2 , R 2 = OMe, R 3 = Cl; c R 1 = NHMe, R 2 = OMe, R 3 = Cl; d R 1 = R 2 = NHEt, R 3 = CN; e R 1 = R 2 = NHCHMe 2 , R 3 = CN; f R 1 = NHEt, R 2 = NHCMe 3 , R 3 = Cl; g R 1 = NMe 2 , R 2 = OMe, R 3 = OC 6 H 4 COOEt-p; h R 1 = NHEt, R 2 = SMe, R 3 = OC 6 H 4 COOEt-p; i R 1 = R 2 = NHCHMe 2 , R 3 = OC 6 H 4 COOMe-p; 2 a R 1 = R 2 = NMe 2 , R 3 = OH; b R 1 = NMe 2 , R 2 = OMe, R 3 = OH; c R 1 = NHEt, R 2 = OMe, R 3 = OH; d R 1 = NHEt, R 2 = OMe, R 3 = OCHMe 2 ; e R 1 = R 2 = NHEt, R 3 = OH; f R 1 = R 2 = NHEt, R 3 = OEt; g R 1 = R 2 = NHCHMe 2 , R 3 = OH; h R 1 = R 2 = NHCHMe 2 , R 3 = OMe; 3 a R 1 = R 2 = NMe 2 ; b R 1 = NMe 2 , R 2 = OMe; c R 1 = NHEt, R 2 = OMe; d R 1 = R 2 = NHEt; e R 1 = R 2 = NHCHMe 2 ; a-e R 3 = Me __________________________________________________________________________________________ Armenian Agricultural Academy, Yerevan 375009;

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