Table 5.

Content of the K form (%) (in CDCl₃ at 303 K), [O] (%) = 100 − [K] (%).

	[K] (%) a
1	94.5 (87.0) b
2	77.5 (83.0) c
3	71.0 (72.0) c; 56 d,e[10]
4	59.0 (57.5) c
5	55.5; 50 d,e[10,13]; 51.5 [20]; 20 d,f[12]
6	53.0 (50.0) c
7	48.0; 33 d,e[10]
8	50.5
9	45.5
10	29.5
11	3.5

^aBased on integrals of the H10 signals (present paper);

^bSince the ¹H NMR chemical shifts for various tautomers differ insignificantly (see Table 4), contributions based on integrals of the N(CH₃)₂ protons are not precise;

^cValues in parentheses are based on integrals of the substituent protons;

^dLiterature data for chloroform solutions at 298 K;

^eOnly K and O tautomers were detected in CDCl₃;

^fThere are three different forms in CDCl₃: [K] + [O] + [E] = 20% + 37% + 43% [12].