Sintesis Isomeros Complejos De Cobre

PREPARATION OF COPPER GLYCINE COMPLEXES Purpose There are two main objectives for this experiment: 1. 2. The preparation of both copper glycine complexes—cis and trans. The analysis of the compoundsto verify which complex is the kinetic product and which one is the thermodynamic product.

Background Like the more familiar acetylacetone, the amino acid glycine, below, dissociates to form ananion (gly) [and cation (H+)], which can coordinate to a wide variety of metal complexes.
O O H C CH2 NH2

One major difference is that the glycine anion is not symmetric and structural isomers canarise depending on the relative orientation of the ligands.
O O O H O M N H H H H N H O O N H

O M N H

O

cis

trans

In this experiment, the cis and trans copper glycinates are prepared.The direct reaction of copper(II) acetate monohydrate and glycine results in an equilibrium mixture of the two isomers. [(CH3CO2)2Cu.H2O]2 + H2NCH2CO2H  cis-Cu(gly)2.H2O + trans-Cu(gly)2.H2O One isomerprecipitates much more quickly than the other, leading to a shift in the equilibrium away from the other, producing only the one isomer. The first isomer (kinetically favored product) is converted tothe other (thermodynamically favored product) simply by heating. Safety Copper(II) acetate monohydrate (CAS No. 66923-668): This compound is harmful if swallowed, inhaled, or absorbed through theskin.

Glycine (CAS No. 56-40-6): No toxicity data is available for this compound, but it would be prudent to follow normal safety precautions. Experimental Preparation of Bis(glycinato)copper(II)Monohydrate (first isomer): Copper(II) acetate monohydrate (2.0 g) is dissolved in 25 mL of hot distilled water. Then 25 mL of ethyl alcohol is added and the solution is kept hot. Dissolve 1.5 g ofglycine in 25 mL of hot water. Mix the two solutions while hot (ca. 70°C). When the solution is cooled on ice, a needle-like precipitate of the first isomer should be obtained. Vacuum filter this mixture...