Organic 2 Review Problem 319

Organic 2 Review Problem 319 - PREPARATIONS 33 Dissolve ca....

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PREPARATIONS 3°3 Dissolve ca. 0-2 g. of product (I) in cold ethanol, and add with shaking 1-2 drops of dilute sulphuric acid. A deep purple coloration appears at once. This shows that salt formation has occurred on the quinoline nitrogen atom to form the cation (!!A), which will form a resonance hybrid with the quinonoid form (!!B). [Note that the forms (!!A) and (IIfi) differ only in electron position, and they are not therefore tautomeric.] If, however, salt formation had occurred on the dimethylamino group to give the cation (III), this charge separation could not occur, and the deep colour would be absent. NMe 2 -NMe, X NMe 2 X ^K /^'CH:CH-^ ^-NMe 2 (UB) " (III) Now add more dilute sulphuric acid drop by drop: the colour almost com- pletely fades, as salt formation occurs on both nitrogen atoms with suppression of the resonance hybrid formation. A wide variety of compounds similar in general type to (IIA-B) but prepared from quinaldine methiodide or ethiodide for greater stability are used as photo-
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.

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