18.4.2 Nucleophilic Substitution at sp2 Carbon Flashcards
Boron has an atomic number of 5. What valence would you expect a boron atom in its ground state to have?
1
Since boron is monovalent, compounds such as BH3 should not exist. How is the existence of BH3 explained?
The 2s orbital hybridizes with two 2p orbitals.
Where R stands for a methyl group, an ethyl group, or some other group. What is the type of hybridization of the central carbon in an ester?
sp2
Ethyl acetate undergoes base induced hydrolysis. The base is “labeled” with an isotope of oxygen. The labeled oxygen is marked with an asterisk.
Which of the choices shows the products with the labeled oxygen in the proper position.
When both are present, why does a nucleophile often attack an sp2 carbon instead of an sp3 carbon?
π bonds are weaker than σbonds.
How is it possible to determine which reaction mechanism is more likely when two or more possible reaction mechanisms are available?
All of the above
Which of the following isotopes is frequently used in choosing between different reaction mechanisms?
Oxygen-18
What is ester hydrolysis?
Converting an ester into a carboxylate salt and alcohol in a basic solution.
Why is base-promoted ester hydrolysis essentially an irreversible reaction?
The carboxylate ion is negatively charged.
In ester hydrolysis, the nucleophile attacks the sp2 carbon even though two sp3 carbons are present. Why?
π bonds are weaker than σ bonds.
