13 C, 15 N coupling constants in substituted 1,2,4‐triazines‐4‐ 15 N

The 13 C, 15 N coupling constants in three 1,2,4‐triazine‐4‐ 15 N derivatives and in a substituted pyrimidine‐1‐ 15 N have been determined and are compared with those in pyridine and quinoline. Of special interest are the data of the 5‐(2‐dimethylamino‐1‐propenyl)‐3,6‐dimethyl‐1,2,4‐triazine‐4‐ 15 N, since one observes a characteristic alternation of the absolute value of J ( 13 C, 15 N) along the sidechain and a hitherto unobserved very large 13 C, 15 N coupling constant through four bonds of 3·9 Hz, the origin of which is attributed to the influence of the lone pair orbital on the 15 N at position 4.