SEQUENCE E The Synthesis of Piperonylonitrile from Piperonyl Alcohol

Purification and Characterization. No further purification of the product is usually necessary. Weigh the product and calculate the crude percent yield. Obtain IR and NMR spectra of the oil. In the NMR, the peaks due to both isomers, if present, can be discerned (see Discussion, Fhrt A). Compare your IR and NMR results with the spectra obtained for the ds-trans mixture formed in Fhrt A and to those recorded in the Corvari et al. reference (see Bibliography) for pure ds-2 -bromostyrene.This reference also gives conditions under which the purity of the material may be more carefully determined by gas chromatography. 

Chemical Tests. Several tests can be mn to determine the presence of unsaturation, aromatic character, and the presence of bromine. Select the appropriate tests from Chapter 9. Do your results confirm the presence of these groups  

1-Chloro-l-phenylethane ionizes easily under El conditions to form a benzylic carbocation intermediate. The ion is stabilized due to the delocalization of the positive charge to the aromatic ring. Draw resonance structures that indicate the stability of this ion. 

Comment on the fact that eryf/zro-2,3-dibromo-3-phenylpropanoic acid undergoes elimination by an El pathway in water solvent (Fhrt A conditions), but by an E2 pathway (Thrt B conditions) when acetone is used as the solvent. 

Explain in terms of the mechanism why conditions in Part A lead to a mbcture of ds-trans isomers but that those used in Fhrt B give only the ds isomer. 

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SEQUENCE E The Synthesis of Piperonylonitrile from Piperonyl Alcohol 493... 

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