Term
Alkene energies are often compared by measuring the __________ __________ __________: the heat given off (delta H) during catalytic hydrogenation.
Heats of hydrogenation can be measured about as easily as __________ __________ __________, yet they are (smaller/larger) numbers and provide more accurate energy differences. |
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Definition
1) Heat of hydrogenation
2) Heats of combustion
3) Smaller |
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Term
| When an alkene is treated with __________ in the presence of a platinum catalyst, __________ adds to the double bond, reducing the alkene to an __________. |
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Definition
1) Hydrogen
2) Hydrogen
3) Alkane |
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Term
| Hydrogenation is mildly __________, evolving about 80 to 120kJ of heat per mole of __________ consumed. |
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Definition
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Term
| The heat of hydrogenation is a measure of the energy content of the __________ bond. |
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Definition
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Term
| We can use __________ __________ __________ to compare the stabilities of different alkenes as long as they hydrogenate to give __________ of similar energies. |
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Definition
1) Heats of hydrogenation
2) Alkanes |
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Term
| The __________ the heat of hydrogenation, the more stable the alkene. |
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Definition
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Term
| The __________ the heat of hydrogenation, the more unstable the alkene. |
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Definition
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Term
The most stable double bonds in alkenes are those with the most __________ groups attached.
Double bonds with __________ alkyl groups hydrogenate to produce about 116-120kJ/mol.
Double bonds with __________ or __________ alkyl substituents further stabilize the double bond. |
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Definition
1) Alkyl
2) Two
3) Three
4) Four |
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Term
| __________ __________ states that the more substituted double bonds are usually more stable. |
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Definition
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Term
| __________ groups attached to the double-bonded carbons stabilize an __________. |
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Definition
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Term
Alkyl groups are __________-donating, and they contribute to __________ __________ to the __________ bond.
In addition, bulky substituents like __________ groups are best situated as far apart as possible; in alkenes, they are often separated by __________. |
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Definition
1) Electron
2) Electron density
3) Pi
4) Alkyl
5) 120 degrees |
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Term
| In general, alkyl groups are separated best by the (least/most) substituted double bonds. |
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Definition
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Term
| __________-__________ isomers are those that differ only in the position of the double bond. |
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Definition
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Term
(Cis/trans) isomers are generally more stable than their corresponding (cis/trans) isomers.
This trend is reasonable because the alkyl substituents are separated farther in (cis/trans) isomers than they are in (cis/trans) isomers. |
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Definition
1) Trans
2) Cis
3) Trans
4) Cis |
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Term
| A __________ difference between cis and trans isomers is typical for __________ alkenes. |
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Definition
1) 4kJ/mol
2) Disubstituted |
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Term
| __________ is the least stable of the simple alkenes. |
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Definition
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Term
Most cycloalkenes react like __________ alkenes.
The presence of a ring makes a major difference only if there is __________ __________, either because of a small __________ or because of a __________ double bond. |
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Definition
1) Acylic
2) Ring strain
3) Ring
4) Trans |
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Term
Rings that are __________-membered or larger can easily accommodate double bonds, and these cycloalkenes react much like __________-__________ alkenes.
__________ and __________ membered rings show evidence of ring strain, however. |
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Definition
1) Five
2) Straight-chain
3) Three
4) Four |
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Term
The double bond in cyclobutene has about __________ of extra ring strain by virtue of the __________ ring.
The __________ bond angles in cyclobutene compress the angles of the __________ hybrid carbons (normally 120 degrees) more than they compress the __________ hybrid angles (normally 109.5 degrees) in cyclobutane.
The extra __________ __________ in cyclobutene makes its double bond more reactive than a typical double bond. |
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Definition
1) 17kJ/mol
2) Small
3) 90 degree
4) sp2
5) sp3
6) Ring strain |
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Term
Cyclopropene has bond angles of about __________, compressing the bond angles of the carbon-carbon double bond to half their usual value __________.
The double bond in cyclopropene is highly __________. |
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Definition
1) 60 degrees
2) 120 degrees
3) Strained |
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Term
In acyclic alkenes, the __________ isomers are usually more stable; but the __________ isomers of small cycloalkenes are rare, and those with fewer than __________ carbon atoms are unstable at room temperature.
The problem with making a trans cycloalkene lies in the geometry of the __________ double bond; the __________ alkyl groups on a trans double bond are so far apart that several carbon atoms are needed to complete the ring. |
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Definition
1) Trans
2) Trans
3) Eight
4) Trans
5) Two |
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Term
| *__________ __________ states that a bridged bicyclic compound cannot have a double bond at a bridgehead position unless one of the rings contains at least eight carbon atoms. |
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Definition
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Term
| Bredt's rule states that a bridged __________ compound cannot have a double bond at a bridgehead position unless one of the rings contains at least __________ carbon atoms. |
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Definition
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Term
A __________ compound is one that contains two rings.
The __________ __________ __________ are part of both rings, with three links connecting them.
A __________ __________ compound has at least one carbon atom in each of the three links between the bridgehead carbons. |
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Definition
1) Bicyclic
2) Bridgehead carbon atoms
3) Bridged bicyclic |
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Term
| If there is a double bond at the __________ carbon of a bridged bicyclic system, one of the two rings contains a __________ double bond and the other must contain a __________ double bond. |
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Definition
1) Bridgehead
2) Cis
3) Trans |
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Term
| In general, compounds that violate __________ __________ are not stable at room temperature. |
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Definition
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