Week 8 txtbk Flashcards
(8 cards)
hydrate
func group formed by the addition of water to a carbonyl group
when an acid like HCl is used in water…
the acid dissociates to form H3O+
hemiacetal
a tetrahedral carbon connected to OH group and an OR group
-rxn same as hydration except the Nuc adds across the carbonyl group is an alc, ROH, rather than water
how do bases accelerate rxn
bases accelerate a reaction by increasing the reactivity of a neutral nucleophile by converting it into its anionic conjugate base.
This conjugate base donates (“pushes”) electrons more readily than the neutral nucleophile
acid catalyst
activates a neutral electrophile by converting it to a positively charged material, which accepts (“pulls”) electrons more readily
During the addition of nucleophiles to carbonyls and related compounds…
the hybridization of the electrophilic carbon changes from sp2 to sp3. This change produces stereogenic centers if this carbon atom has four different substituents. Therefore, two product stereoisomers may be possible.
key rxn pathway in Nuc. addition
The key reaction pathway involves the addition of a nucleophile to the most electrophilic atom of the double bond, while the π bond of the double bond breaks
patterns in Nuc additions (acid conditions)
Basic lone pairs on the most Nuc. atom of the double bond first react with an acid
–this rxn activates Elec. group, enabling it to accept electrons more readily
The Nuc. adds to the Elec. carbon, in the process breaking the π bond in the same manner as in a base-catalyzed process
–the result is often a positively charged intermediate that becomes neutral by giving up a proton in a later step
The bond between the hydrogen and the positively charged atom is broken by a flow of electrons onto the positively charged atom since it is very electronegative
–this flow neutralizes the positive charge on that atom
