Addition reaction mechanisms help please?
Hello!
I was writing up my notes from my last chem class and became curious about the mechanism for the reaction between ethene and hydrogen over a nickel catalyst.
I tried Googling it but my efforts proved fruitless :/
If someone could take me through the mechanism for this reaction I would be very grateful!
Thank you
I was writing up my notes from my last chem class and became curious about the mechanism for the reaction between ethene and hydrogen over a nickel catalyst.
I tried Googling it but my efforts proved fruitless :/
If someone could take me through the mechanism for this reaction I would be very grateful!
Thank you
Original post by DayFlower
Hello!
I was writing up my notes from my last chem class and became curious about the mechanism for the reaction between ethene and hydrogen over a nickel catalyst.
I tried Googling it but my efforts proved fruitless :/
If someone could take me through the mechanism for this reaction I would be very grateful!
Thank you
I was writing up my notes from my last chem class and became curious about the mechanism for the reaction between ethene and hydrogen over a nickel catalyst.
I tried Googling it but my efforts proved fruitless :/
If someone could take me through the mechanism for this reaction I would be very grateful!
Thank you
The ethene coordinates to the metal surface 'weakening' the bond making it easier to attack with hydrogen. The hydrogen is more reactive because it 'dissociates' into singular H's on the metal surface rather than H2.
H2 has van der waals forces acting on it, so one H is partially positively charged and attracted to the electron dense double bond. you draw a curly arrow FROM the hydrogen to the double bond. Then youre left with a primary carbocation and a partially negatively charged hydrogen atom. Both are attracted to each other. Final arrow goes from H to carbocation, forming ethane.
No. The nickel acts as a heterogeneous catalyst (ie. it's in a different state of matter (phase) than the reagents). It catalyses the reaction, like any catalysts do, by providing an alternative pathway with lower activation energy. The ethene adsorbs onto the surface of the hot catalyst in active sites. This interaction breaks the double bonds and makes the addition reaction possible. The hydrogen atoms also adsorb onto the Nickel surface and they break the bonds between themselves, meaning they are no longer a diatomic molecule which allows them to move around on the surface of the catalyst. After the reaction has happened, the products desorb from the surface. This also increases the rate of the reaction as the ethene molecule is always in the correct orientation and it increases the number of collisions as all the reagents are adsorbed into the surface of the catalyst.
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