Posted 18 November 2005 - 08:04 AM
When an Alkyne reacts with H2 gas over a Lindlar catalyst, the reaction stops (according to what I have read, and what my professor has said) at the alkene - it does not proceed to the alkane, whereas with a catalyist like PtO2, it will reduce the element all the way down to an alkane (at least, in some cases, as I understand it). Is the difference in the mechanism the electophilic nature of the catalyst? Is a Lindlar catalyst electrophilic enough to attract a triple bond, but not enough to lock onto a double bond? The sources I have read talk about "poisoning" the catalyst, and this confuses me. Is it a different catalyst (a "weakened" palladium?) that nevertheless acts as a catalyst should (and is not changed at all in the process), or is something happening to the catalyist itself, reducing it's ability to function? The latter is how I have heard it described, but I suspect I may have misunderstood.
Thank you in advance for any help!