Organic Lab Reactions 282

Organic Lab Reactions 282 - REDUCTION WITH HYPOPHOSPHOROUS...

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Unformatted text preview: REDUCTION WITH HYPOPHOSPHOROUS ACID 277 biaryls. 68- ** 74- 76 In the ethanol decompositions of zinc chloride- diazonium chloride double salts, the addition of zinc dust is reported to overcome the influence of substituents; only reduction occurs. 79 Zinc oxide is helpful in the deamination of hydroxybenzenediazonium salts. 41 Aluminum powder is sometimes added to advantage. 66 The use of these substances is unquestionably beneficial in many in- stances, but the utility of most of them is limited; in fact, certain reduc- tions are adversely affected by the addition of promoters. 66- 76 ' 66 Acids and Bases. Concentrated sulfuric acid is sometimes added to the alcohol, especially when the diazonium salt is isolated and dried before reduction. 62- 77- 78 In the presence of sodium ethoxide, sodium hydroxide, or sodium car- bonate, little, if any, ether formation occurs. There is, however, a marked increase in the yields of biaryJs and tars so that these bases are of no real value in bringing about deaminations.of no real value in bringing about deaminations....
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