Quiz - Delocalized π Systems and Dienes - 2 | Delocalized π Systems and Dienes
Organic Chemistry 2 - Quiz - Delocalized π Systems and Dienes - 2
Which statement best explains the stability of the allyl system?
Allyl systems have a π-electron cloud that is delocalized over three carbon atoms, which forms a conjugated π system. This delocalization provides resonance stabilization to the allyl system, decreasing the overall energy and increasing stability.
During an electrophilic addition to a conjugated diene, which type of product predominates at low temperatures?
At low temperatures, the reaction is under kinetic control, favoring the formation of products that are formed quickly. These are typically the less substituted and therefore less stable kinetic products.
In a Diels-Alder reaction, what type of orbitals overlap to form the new sigma bonds?
In the Diels-Alder reaction, new σ bonds are formed by the overlap of the p-orbitals of the diene with the p-orbitals of the dienophile, as both partners need to participate in a [4+2] cycloaddition.
Which term describes the location of an sp3 hybridized carbon atom, one position removed from a double bond, and where nucleophilic substitution typically occurs?
An allylic position is an sp3 hybridized carbon atom adjacent to a double bond (one position removed). This carbon is often the site of nucleophilic substitution due to the resonance stabilization of intermediates.
What is the term for the energy difference between the highest occupied molecular orbital of the diene and the lowest unoccupied molecular orbital of the dienophile in a Diels-Alder reaction?
The HOMO-LUMO gap is the energy difference between the diene's highest occupied molecular orbital (HOMO) and the dienophile's lowest unoccupied molecular orbital (LUMO). A smaller HOMO-LUMO gap typically indicates a more favorable interaction and a faster Diels-Alder reaction.
Which is true regarding the reaction of dienes with electrophiles?
Conjugated dienes offer two reaction sites for electrophiles, the 1,2-position and the 1,4-position. The position at which the electrophile adds depends on the conditions and the control (kinetic or thermodynamic) of the reaction.
How does conjugation affect the absorption spectrum of a molecule in UV-Visible spectroscopy?
The amount of energy is inversely proportional to the wavelength. Conjugation lowers the energy of the π-electrons due to delocalization, which results in a longer wavelength (red-shift) needed for electronic transitions in the UV-Visible spectrum.
Following a Diels-Alder reaction, how are the stereochemistry of the diene and dienophile reflected in the product?
The Diels-Alder reaction has a concerted mechanism where bonds form simultaneously, thus preserving the relative stereochemistry of the diene and the dienophile in the product.
When considering kinetic vs. thermodynamic control in the reaction of dienes, what factor predominantly influences the formation of the kinetic product at low temperatures?
At low temperatures, kinetic control predominates, and the kinetic product is favored due to having a lower activation energy and forming more quickly than the thermodynamic product.