Poisoning with lead

Lindlar catalyst (Section 9 9) A catalyst for the hydrogenation of alkynes to as alkenes It is composed of palladium which has been poisoned with lead(II) acetate and quino line supported on calcium carbonate... 

In his 1980 dissent, Patterson warned that it is probable that (the middle) person is also poisoned with lead, but in more subtle ways that have not yet been disclosed. He called for the phase-out of lead mining, smelting, and manufacturing, a monumental crime committed by humanity against itself. Only two committee members, Cliff Davidson of the Carnegie Institution and Jerome Nriagu of the University of Michigan, endorsed Patterson s position. 

Deknudt G, Colle A, Gerber GB. 1977. Chromosomal abnormalities in lymphocytes from monkeys poisoned with lead. Mut Res 45 7-83. 

Lindlar s catalyst metallic palladium deposited on calcium carbonate and is poisoned with lead acetate and quinoline. 

Z)-Methyl styrene was easily obtained by hydrogenation of 1-phenyl-1-propyne using Lindlar s catalyst (5% palladium on calcium carbonate, poisoned with lead) in //-hexane under an atmospheric pressure of hydrogen. The mixture, containing 90% of (Z)-methyl styrene and 10% of the overreduced alkane, was used without further purification. 

Alkynes may also be hydrogenated, initially to alkenes, and then further to alkanes. By suitable modification of the catalyst, it has proved possible to stop the reaction at the intermediate alkene. Typically, platinum or palladium catalysts partially deactivated (poisoned) with lead salts are fonnd to be suitable for reduction of alkynes to alkenes. Again, syn addition is observed. 

On administration of 0.1 and 0.01% of l-(0,0-diethylphosphonemethyl)-3,7,10-trimethylsilatrane in physiologic saline solution to the blood of animals poisoned with lead nitrate a sharp increase in acid resistance of erythrocytes was oberved (Fig. 7) along with erythrogram shift to the right and a prolonged prelytic time (to 240 60 sec). Sometimes the maximum erythrocytolysis occurs only after 300 60 sec. Haemolysis is completed in 720 30 sec. 

X You will meet Lindlar s catalyst in Chapter 31 but we will mention it now because of its special chemoselectivity. Unlike the other hydrogenations we have described, the Lindlar catalyst will hydrogenate alkynes to alkenes, rather than alkenes to alkanes. This requires rather subtle chemoselectivity alkenes are usually hydrogenated at least as easily as alkynes, so we need to be sure the reaction stops once the alkene has been formed. The Lindlar catalyst is a palladium catalyst (Pd/CaC03) deliberately poisoned with lead. The lead lessens the activity of the catalyst and makes further reduction of the alkene product slow most palladium catalysts would reduce... 

Citronellal, an aldehyde with a trisubstituted double bond, was hydrogenated to citronellol over a ruthenium catalyst poisoned with lead acetate in 90-100% yields (eq. 5.22)46 or over chromium-promoted Raney Ni in 94% yield in methanol at 75°C and about 0.31 MPa H2.47 Court et al. studied the selective hydrogenation of citral (1, eq. 5.24) to citronellol over unsupported Nij. o catalysts, prepared by reduction of mixtures of metal iodides with naphthalene-sodium as reducing agent, in cyclohexane and in 2-propanol at 80°C and 1.0 MPa H2.48 Higher yields of citronellol were obtained in 2-propanol than in cyclohexane, primarily via citronellal as the predominant intermediate. The yields of citronellol for the overall hydrogenation in 2-propanol over Mo-promoted catalysts were Mo0 03 96%, Mo0 06 98%, and Mo012 96%. 

Lead raw glazes are often used for ceramic art ware, but seldom on an industrial scale owing to the danger of poisoning with lead compounds. If a lead glaze is to be used, it is more convenient to introduce PbO into the glaze in the form of a pre--melted frit. 

Biochemical effects of lead result in changes of the activity of enzymes, where lead may be bound to both functional and structural proteins or it can displace essential metals from biological molecules and destroy the structural function relationships of nucleic acids. The poisoning with lead can involve the haemopoietic system, central nervous system (encephalopathy), kidneys, gastrointestinal tract, cardiovascular system, etc. 

Other partially poisoned catalysts have long been used in the laboratory. Supported palladium catalysts, poisoned with lead (Lindlar catalysts), sulfur, or quinoline, are used for the hydrogenation of acetylenic compounds to cis-olefins. Another... 

A detailed study of the hydrogenation of valylene (2-methyl-but-l-ene-3-yne) and isoprene has shown that palladium catalysts poisoned with lead can give highly chemoselective reductions. ... 

Poisoning with lead affects porphyrin metabolism. The direct action of Pb++ (10 M) on chicken erythrocytes is to cause complete inhibition of fi-AL synthesis. There is also an inhibition of PROTO synthe from 3-AL possibly due to reaction with essential SH groups of 3-ALase. There is only sli t inhibition of PROTO synthesis from PBG (96),... 

Przybylowski, J., Kowalski, W., Podolecki, A., Effect of Chronic Experimental Poisoning with Leaded and Straight Gasoline Vapors on the Circulatory System, Patol. Pol. 27 [1976] 149/56 C.A. 85 [1976] No. 88185. 

Pratt, O. E. (1985) Continuous-injection methods for the measurement of flux across the blood-brain barrier. The steady-state, initial-rate method. In Marks, N. and Rodnight, R. (eds). Research Methods in Neurochemistry, vol. 6 (New York-London Plenum Press) Saunders, N. R. (1977) Ontogeny of the blood-brain barrier. Exp. Eye Res., (SuppL), 523-550 Silbergeld, E. K., Wolinsky, ]. S. and Goldstein, G. W. (1980) Electron probe microanalysis of isolated brain capillaries poisoned with lead. Brain Res., 189, 369-376 Simons, T. J. B. (1986) Passive transport and binding of lead by human red blood cells. ]. 

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