Concept explainers
(a)
Interpretation:
The mechanism for the reaction that will take place when the given compound is treated with
Concept introduction:
Diazomethane,
The stereochemistry of the double bond is preserved in the addition. If the double bond has a cis relationship, then the two substituents end up on the same side of the cyclopropane ring. If the two substituents on the double bond are trans to each other, they end up on the opposite sides of the cyclopropane ring. This also determines the product distribution if the cyclic product is chiral. If the starting
Answer to Problem 12.26P
The mechanism for the reaction when
Explanation of Solution
Diazomethane dissociates heterolytically when irradiated with ultraviolet light to produce a carbene and a nitrogen molecule.
The carbene then simultaneously adds to the initially double-bonded carbons. The lone pair on the carbene forms a bond with one carbon while the
Since the starting alkene is chiral, the product will be a mixture of two enantiomers. The pair of enantiomers is produced because the carbene can add either above or below the plane of the ring in the reactant.
Thus the complete mechanism for this reaction can be drawn as
A carbene adds to an alkene or
(b)
Interpretation:
The mechanism for the reaction that will take place when the given compound is treated with
Concept introduction:
Diazomethane,
The stereochemistry of the double bond is preserved in the addition. If the double bond has a cis relationship, then the two substituents end up on the same side of the cyclopropane ring. If the two substituents on the double bond are trans to each other, they end up on the opposite sides of the cyclopropane ring. This also determines the product distribution if the cyclic product is chiral. If the starting alkene is achiral and the product chiral, the product is a racemic mixture of enantiomers. If the starting alkene is also chiral, then an unequal mixture of enantiomers is produced.
Answer to Problem 12.26P
The mechanism for the given reaction is
Explanation of Solution
Diazomethane dissociates heterolytically when irradiated with ultraviolet light to produce a carbene and a nitrogen molecule.
The carbene then simultaneously adds to the initially double-bonded carbons. The lone pair on the carbene forms a bond with one carbon while the
The carbene then simultaneously adds to the initially double-bonded carbons. The lone pair on the carbene forms a bond with one carbon while the
Since the starting alkene is chiral, the product will be a mixture of two enantiomers. The pair of enantiomers is produced because the carbene can add either above or below the plane of the ring in the reactant.
Thus the complete mechanism for this reaction can be drawn as:
A carbene adds to an alkene or alkyne to produce a cyclopropane ring.
(c)
Interpretation:
The mechanism for the reaction that will take place when the given compound is treated with
Concept introduction:
Diazomethane,
The stereochemistry of the double bond is preserved in the addition. If the double bond has a cis relationship, then the two substituents end up on the same side of the cyclopropane ring. If the two substituents on the double bond are trans to each other, they end up on the opposite sides of the cyclopropane ring. This also determines the product distribution if the cyclic product is chiral. If the starting alkene is achiral and the product chiral, the product is a racemic mixture of enantiomers. If the starting alkene is also chiral, then an unequal mixture of enantiomers is produced.
Answer to Problem 12.26P
The mechanism for the given reaction is
Explanation of Solution
Diazomethane dissociates heterolytically when irradiated with ultraviolet light to produce a carbene and a nitrogen molecule.
The carbene then simultaneously adds to the initially double-bonded carbons. The lone pair on the carbene forms a bond with one carbon while the
Only one product is formed in this case because of the symmetry of the reactant alkene about the axis of the double bond.
Thus, the complete mechanism for the given reaction can be drawn as
A carbene adds to an alkene or alkyne to produce a cyclopropane ring.
(d)
Interpretation:
The mechanism for the reaction that will take place when the given compound is treated with
Concept introduction:
Diazomethane,
The stereochemistry of the double bond is preserved in the addition. If the double bond has a cis relationship, then the two substituents end up on the same side of the cyclopropane ring. If the two substituents on the double bond are trans to each other, they end up on the opposite sides of the cyclopropane ring. This also determines the product distribution if the cyclic product is chiral. If the starting alkene is achiral and the product chiral, the product is a racemic mixture of enantiomers. If the starting alkene is also chiral, then an unequal mixture of enantiomers is produced.
Answer to Problem 12.26P
The mechanism for the given reaction is
Explanation of Solution
Diazomethane dissociates heterolytically when irradiated with ultraviolet light to produce a carbene and a nitrogen molecule.
The carbene then simultaneously adds to the initially double-bonded carbons. The lone pair on the carbene forms a bond with one carbon while the
The starting alkene has a trans geometry, therefore, the two substituents on the cyclopropane ring in the product are on opposite sides of the ring.
This means the product is chiral, and a racemic mixture of two enantiomers will be produced.
Thus, the complete mechanism for the reaction can be drawn as
A carbene adds to an alkene or alkyne to produce a cyclopropane ring.
(e)
Interpretation:
The mechanism for the reaction that will take place when the given compound is treated with
Concept introduction:
Diazomethane,
The stereochemistry of the double bond is preserved in the addition. If the double bond has a cis relationship, then the two substituents end up on the same side of the cyclopropane ring. If the two substituents on the double bond are trans to each other, they end up on the opposite sides of the cyclopropane ring. This also determines the product distribution if the cyclic product is chiral. If the starting alkene is achiral and the product chiral, the product is a racemic mixture of enantiomers. If the starting alkene is also chiral, then an unequal mixture of enantiomers is produced.
Answer to Problem 12.26P
The mechanism for the given reaction is
Explanation of Solution
Diazomethane dissociates heterolytically when irradiated with ultraviolet light to produce a carbene and a nitrogen molecule.
The carbene then simultaneously adds to the initially double-bonded carbons. The lone pair on the carbene forms a bond with one carbon while the
The starting alkene has a cis geometry and is symmetric. Therefore, only one product, a meso compound is produced.
Thus the complete mechanism for this reaction can be drawn as
A carbene adds to an alkene or alkyne to produce a cyclopropane ring.
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Chapter 12 Solutions
ORGANIC CHEMISTRY:PRIN...(PB)-W/ACCESS
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