Geometrical lsomers of Pentachlorobenzaldehyde Oxime

Abstract

Lock obtained an isomerof 2, 3, 4, 5, 6-pentachlorobe: nzaldehyde oxime l a by oximation of 2, 3, 4, 5, 6-pentachlorobenzaldehyde 2 with hydroxylamine, but its con guration has not been clari ed. We obtained another iso: mer l b by oximationof 2 with hydroxylamine sulfonate 3. When the velocities of the de-acetic acid reaction to obtain nitrile 6 in pyridine of the acetate 5 a was compared with that of 5 b, we observed that 5 b completely changed, into 6 at 24 C f r an hr, but 5 a at 1150C for an hr. On heating, 5 a and 5b changed. to 6 and obviously the velocity of 5 b to change into 6 higher than that of 5 a Their NMR spectra showed general patterns of geometrical isomers of oximes, (DMSO-d6) 1 a 8.1(s, 1H, -CH=), 12.0(s, 1H, -OH); 1 b 7.6(s, 1H, -CH=) 11.8(s, 1H, -OH). Accordingly la and 1 b have Syn-and anti-con g, uratio: n, respectively. l b isomerized completely to 1a by heating it at the melting Point and then, by keeping it, and during the oxi ation reactions at higher temperatures. l a isomerized to l b by ultra-violet light. In Table 1, 1a / 1 b ratios under various reaction conditio: ns are shown.