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The reaction of zinc with water is slowed by this passive layer. When this layer is corroded by acids such as hydrochloric acid and sulfuric acid, the reaction proceeds with the evolution of hydrogen gas. [1] [9] Zn + 2 H + → Zn 2+ + H 2. Zinc reacts with alkalis as with acids.
The reaction produces a primary, secondary, or tertiary alcohol via a 1,2-addition. The Barbier reaction is advantageous because it is a one-pot process: the organozinc reagent is generated in the presence of the carbonyl substrate. Organozinc reagents are also less water sensitive, thus this reaction can be conducted in water.
The oxygen on an aldehyde or ketone coordinates to the zinc to form the six-member chair like transition state 3. A rearrangement occurs in which zinc switches to the aldehyde or ketone oxygen and a carbon-carbon bond is formed 4. Acid workup 5,6 removes zinc to yield zinc(II) salts and a β-hydroxy-ester 7. [5]
The Negishi coupling was implemented in the synthesis of δ-trans-tocotrienoloic acid by Hecht and Maloney coupling the sp 3 homopropargyl zinc reagent 8 with sp 2 vinyl iodide 9. [43] The reaction proceeded with quantitative yield, coupling fragments mid-synthesis en route to the stereoselectively synthesized natural product δ-trans ...
Most side reactions occur due to the Lewis-acidity of the byproduct, ZnI 2. In reactions that produce acid-sensitive products, excess Et 2 Zn can be added to scavenge the ZnI 2 that is formed, forming the less acidic EtZnI. The reaction can also be quenched with pyridine, which will scavenge ZnI 2 and excess reagents. [24]
A recent example showed 6 micromolar killing 93% of all Daphnia in water. [245] The free zinc ion is a powerful Lewis acid up to the point of being corrosive. Stomach acid contains hydrochloric acid, in which metallic zinc dissolves readily to give corrosive zinc chloride.
[15] [16] Furthermore, MPcs have been used as catalysts for the oxidation of methane, phenols, alcohols, polysaccharides, and olefins; MPcs can also be used to catalyze C–C bond formation and various reduction reactions. [17] Silicon and zinc phthalocyanines have been developed as photosensitizers for non-invasive cancer treatment. [18]
Zinc trifluoromethanesulfonate or zinc triflate is the zinc salt of trifluoromethanesulfonic acid.It is commonly used as a Lewis acid catalyst, e.g. in silylations. [1]A white powder, zinc triflate is commercially available, though some workers have experienced inconsistent results with zinc triflate from different sources.