X-Ray Crystal Structures of a 1-(p-fluorophenyl)-2-(α-pyridyl)ethanol Intermediate and the 1-(p-fluorophenyl)-2-(α-pyridyl)ethene Dehydration Compound Obtained from the Condensation Reaction of 2-Methylpyridine and p-Fluorobenzaldehyde

Abstract

The compound 1-(p-fluorophenyl)-2-(�-pyridyl)ethanol and its corresponding dehydration compound 1-(p- fluorophenyl)-2-(�-pyridyl)ethene were obtained from the Knoevenagel condensation reaction between 2-methylpyridine with p-fluorobenzaldehyde. The X-ray structure determined for 1-(p-fluorophenyl)-2-(�-pyridyl)ethanol reveals that the compound crystallizes in the monoclinic system space group, P21/n, containing four molecules in each crystal unit cell (a = 5.3664(15) A, b = 8.343(2) A, c = 25.056(6) A, and  = 93.837(15)°). The crystal structure shows the formation of an intermolecular hydrogen bond O-H … N between the oxygen atom of the O-H and the nitrogen atom of a pyridine group of the next molecule. The condensation product 1-(p-fluorophenyl)-2-(2-pyridyl)ethene crystallizes in the monoclinic sys- tem, in the Cc space group, with unit cell dimensions a = 22.920(7) A, b = 5.9149(14) A, c = 7.8544(15) A, and  = 104.16(2)°. The molecular structure shows the p-fluorophenyl ring attached to the double bond and located trans to the pyridine ring. The crystallography data give evidence that the intermediary compound is actually the alcohol just before the dehydration process that yields the trans double bond of the 1-(p-fluorophenyl)-2-(� -pyridyl)ethene.