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25 Cards in this Set
- Front
- Back
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How do you Hydrogenate an alkyne to a cis alkene?
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Use Lindlars's catalyst
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What is a Lindlar's catalyst, what is it used for and what is the stereochemistry
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Pt or Pd plus quinoline and lead acetate
Hydrogenates an alkyne to an alkene. Syn stereochemistry 2-butyne would become cis-2-butene |
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How do you hydrogenate an alkyne to the trans alkene
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Na in liquid NH3
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What will remove the acidic proton from a terminal alkyne
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A very strong base like NH2-
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How do you make NH2-
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NH3 + Na and a Fe3+ catalyst
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Addition of acetylide to carbonyl groups is dictated by
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electronics.
The double bond to Oxygen makes the O slightly negative and the C slightly positive. |
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the addition of acetylide to a carbonyl produces . . .
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an alcohol and the alkyne attached.
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describe the addition of an alkyne to a carbonyl
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NH2- takes proton turning alkyne to acetylide, this is added carbonyl is added. Acetylide attacks the C double bonded to O. Oxygen gets the electrons from the double bond and becomes O-. Acid is added to protonate the Oxygen to make an alcohol.
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When adding an alkyne to a carbonyl must it be a primary carbonyl?
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Nope
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How do you form a triple bond
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Double dehydrohalogenation of a dihalide
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Describe the 2 conditions to produce a triple bond
Where does each one favor the triple bond. |
Start with a dihalide
200 Celsius with molten (fused) KOH. Multiple isomerizations produce all possible locations for triple bond but favor the most stable. 150 Celsius with NaNH2. Then quench reaction by adding water. Favors primary triple bond. |
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Describe the process to form a triple bond
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The base abstracts a proton then a X leaves making a double bond. This happens again and the triple bond is formed.
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What are the processes to hydrogenate an alkyne and how do you control the product to make a cis or trans alkene
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Pt, Pd, or Ni will reduce them all the way
To produce the cis add H2, Pd/BaSO4 (or Ni2B) quinoline in an alcohol. to produce the trans alkene add Na in liquid NH3 |
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What do you add to the mix to produce a cis alkene from an alkyne
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H2 + Pd/BaSO4 + quinoline + CH3OH
or Ni2B |
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to produce a trans alkene from an alkyne what do you add
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Sodium metal in liquid ammonia
(Na in NH3) |
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Describe the mechanism for production of a trans alkene from an alkyne
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Done in NH3 and Na. Electron adds to alkyne forming a radical anion.
NH3 donates a H to the lone pair leaving a radical on the other C. An electron adds to the radical forming an anion. NH3 protonates the anion making a trans alkene. |
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When adding HX to primary alkyne what usually results
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X adds to the markovnikov position
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When adding HX to an alkyne in the presence of a peroxide what results
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radical is produced on the alkene and the X radical is added to the anti-markovnikov position.
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2 types of addition of HX to an alkyne
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ionic addition and radical addition.
Similar to alkenes. |
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What is tautomerization
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When an enol and a keto will interconvert. The carbon double bonded to carbon with a single OH is not terribly stable. A Hydrogen will move to the other C to make a double bond to the O.
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How do you produce a alpha diketone
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Add a neutral aqueous solution of potassium permanganate to an alkyne.
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What happens if you add cold neutral KMnO4 to a triple bond
specify for internal and external |
Makes a diketone if it is internal and a ketone and a carboxylic acid in a terminal triple bond.
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What happens if you add hot basic KMnO4 to a triple bond
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Cleave the triple bond and make a carboxylic acid on each end.
If the triple bond is terminal the terminal carbon leaves as CO2. |
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What happens if you add O3 to a triple bond
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Cleaves the bond and makes both sides into a carboxylic acid. A terminal triple bond does not have a CO2 leave instead the single carbon leaves as Formic acid (CHCOOH).
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What are the steps to cleaving a triple bond with O3
And what are the products |
First add the O3.
Second add H2O 2 carboxylic acids |
