Term
| __________ is a molecule which adds to alkenes to give __________-__________ orientation to form alkylboranes, which can be oxidized to give anti-Markovnikov __________. |
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Definition
1) Diborane
2) Anti-Markovnikov
3) Alcohols |
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Term
__________ is a dimer composed of two molecules of borane (BH3)
The bonding in __________ is unconventional, using three-centered (banana-shaped) bonds with __________ in the middle of them.
Diborane is in equilibrium with a small amount of __________, a strong Lewis acid with only six valence electrons.
However __________ is an inconvenient reagent as it is toxic, flammable, and an explosive gas.
It is more easily used as a complex with __________, a cyclic ether. |
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Definition
1) Diborane
2) Diborane
3) Protons
4) Borane
5) Diborane
6) THF |
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Term
The BH3*THF reagent is the form of borane commonly used in organic reagents.
BH3 adds to the double bond of an alkene to give an __________.
Basic __________ __________ oxidizes the alkylborane to an __________.
In effect, __________-__________ converts alkenes to alcohols by adding water across the double bond, with __________-__________ orientation. |
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Definition
1) Alkylborane
2) Hydrogen peroxide
3) Alcohol
4) Hydroboration-oxidation
5) Anti-Markovnikov |
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Term
__________ is an electron-deficient compound with only six valence electrons.
Acquiring an __________ is the driving force for the unusual bonding structures found in __________ compounds.
As an electron-deficient compound, __________ is a strong electrophile, capable of adding to a double bond.
This __________ of the double bond is though to occur in one step (concerted) with the boron atom adding to the (less/more) substituted end of the double bond. |
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Definition
1) Boron
2) Octet
3) Boron
4) Borane
5) Hydroboration |
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Term
| __________ of the double bond is a reaction which occurs in a single step in which a boron atom adds to the less substituted end of the double bond of an alkene. |
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Definition
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Term
In the hydroboration transition state, the electrophilic __________ atom withdraws electrons from the __________ bond of an alkene, and the carbon at the other end of the double bond acquires a partial __________ charge.
This charge is more stable on the (less/more) substituted carbon atom.
The product shows boron bonded to the (less/more) substituted end of the double bond and hydrogen bonded to the (less/more) substituted end.
__________ __________ also favors boron's placement to the (less/more) substituted end of the double bond as well. |
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Definition
1) Boron
2) Pi
3) Positive
4) More
5) Less
6) More
7) Steric hinderance
8) Less |
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Term
*Mechanism 8-6: Hydroboration of an Alkene*
__________ adds to the double bond in a single step, adding to the (less/more) substituted carbon with hydrogen adding to the (less/more) substituted carbon.
The boron atom is then removed by oxidation, using aqueous __________ __________ and __________ __________ to replace the boron atom with a __________ group |
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Definition
1) Boron
2) Less
3) More
4) Sodium hydroxide
5) Hydrogen peroxide
6) Hydroxyl |
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Term
| The hydration of an alkene by hydroboration-oxidation is another example of a reaction that does not follow __________ __________; however, we know that it follows Markovnikov's principle as the electrophilic __________ atom adds to the (less/more) substituted end of the double bond, placing the positive charge (and __________ atom) at the (less/more) substituted end. |
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Definition
1) Markovnikov's rule
2) Boron
3) Less
4) Hydrogen
5) More |
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Term
Each B-H bond in BH3 can add across the double bond of an alkene; the first addition forms an __________, the second a __________, and the third a __________.
__________ react as discussed, oxidizing to give anti-Markovnikov __________. |
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Definition
1) Alkylborane
2) Dialkylborane
3) Trialkylborane
4) Trialkylboranes
5) Alcohols |
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Term
| A __________ addition is when boron and hydrogen add to the double bond of an alkene on the same side of a molecule. |
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Definition
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Term
| A __________ addition is when boron and hydrogen add to the double bond of an alkene on opposite sides of a molecule. |
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Definition
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Term
| A __________ mixture is expected whenever a chiral product is formed from achiral reagents. |
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Definition
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Term
Hydroboration-oxidation of 1-methylcyclopentene:
First, __________ and __________ add to the same face of the double bond (__________) creating a trialkylborane.
Oxidation of the trialkylborane replaces boron with a __________ group in the same stereochemical position, creating a __________ mixture.
The second step (oxidation of the borane to the __________) takes place with __________ of configuration.
__________ ion adds to the borane, causing the alkyl group to migrate from boron to __________.
The alkyl group migrates with __________ of configuration because it moves with its electron pair and does not alter the tetrahedral structure of the migrating carbon atom.
Hydrolysis of the borate ester gives the __________. |
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Definition
1) Hydrogen
2) Borane
3) Syn
4) Hydroxyl
5) Racemic
6) Alcohol
7) Retention
8) Hydroperoxide
9) Oxygen
10) Retention
11) Alcohol |
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Term
| Hydroboration of alkenes is another example of a __________ __________ in which different stereoisomers of the starting compound react to give different stereoisomers of the product. |
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Definition
| 1) Stereospecific reaction |
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