Experiment 2- Catalytic Alkene Hydrogenation Flashcards
Define Hydrogenation
Addition of the H2 molecule across a unit of unsaturation (examples of unsaturation are alkenes and carbonyls).
What is another way to view unsaturation?
To see all the carbons that as sp^3 hybridized.
What are triacylglycerides?
They are fats, made from condensing glycerol with 3 molecules of fatty acids.
Triacylglycerides with _____ are unsaturated and are considered good fats.
Cis-Alkenes
What is the allylic position in alkenes?
The position adjacent to the carbon involved in the double bond.
Why are unsaturated fats considered worst than saturated fats?
This is becasue they have a shorter shelf life. The reason for this is the allylic hydrogens in the alkene are susceptible to oxidation, rendering the oil rancid upon the reaction.
What are all oils consisted of?
Saturated and unsaturated fats.
Can unsaturated fats contain trans alkenes?
Yes, they can.
What is INCORRECT about unsaturated fats?
They are STABLE.
What are the bad things that can happen when you have alkenes present (unsaturation) in oils?
Light can convert the cis-alkene into a trans-alkene, effectively making it a trans fat. Also, the hydrogen on the allylic position can be oxidized, rendering the oil rancid.
What happens with hydrogenation reactions?
The double bond is broken and hydrogens are added across the double bond.
What can happen with he hydrogenation of oils?
Some of the cis-alkenes can partially isomerize into trans-alkenes. Since trans-alkenes are more stable, they are harder to hydrogenate.
What is being done in this experiment?
Hydrogenation of Ethyl Cinnamate through palladium catalysis.
What does the suffix “ate” refer to?
Refers to the CO2 motif in esters.
What are the reaction conditions for this experiment? Why does this deviate from the norm?
The source of hydrogens will be ammonium formate as opposed to molecular hydrogen. Molecular hydrogen + oxygen lead to a highly exothermic reaction.
Define Transfer Hydrogenation
A reaction in where hydrogen is transferred from one entity to the other is called a transfer hydrogenation.
What happens in the ammonium formate-mediated transfer hydrogenation scheme?
The lone pair on the oxygen from the formate turns into a pi bond, making CO2. From there, the C-H bond is broken, so that a hydride is transferred to the palladium. Then, the negatively charged hydrogen does a proton transfer onto ammonium, leading to the presence of 2 hydrogen on the surface of palladium.
Does ammonium formate contain an H-H bond?
No, it does not. The ammonium cation contains the H+ and the formate anion contains the H- .
Define Reduction Reactions.
Hydrogenation reactions where carbons form new bonds to hydrogen are called reduction reactions.
What is the role of Pd/C in this experiment
It is sued for the hydrogenation process.
What does the term “reflux” refer to?
It means the boiling and immediate condensation of the solvent.
Where does water flow take place in the condenser? How must the tubes be oriented?
From bottom to up. The bottom tube allows for the flow of water, whereas the top tube allows for the water to be moved out.
Between Diethyl Ether (Et2O) and water, which make the organic adds aqueous layer respectively?
Et2O makes the organic layer and H2O makes the aqueous layer.
Define Chromophore
The part of the molecule that is responsible for absorbing the light is called the chromophore.
