04/30/2024 Flashcards
Halohydrins and Carbenes
What is halogenation and what are its features
it is the addition of a halogen (typically Br2 or Cl2) to an alkene.
It follows an anti addition and a cyclicbromonium ion formation
it has a similar mechanism to an SN2 reaction where the bromide ion attacks the cyclicbromonium ion from the back
What is a halohydrogenation and what are the features
it is an anti addition oh Br2 in an H20 solvent
rather than the bromide acting as nucleophile, the h20 is in abundance and acts as a nucleophile to add a h20 to the backside of the cyclicbromonium ion
in a hydrohalogenation, what is acting as a nucleophile
the h20 is in abundance and will preform the backside attack rather than the Br- anion
is a cyclicbromonium ion stable or unstable? why?
it is unstable because it is a 3 membered ring, it wants to open so it is reactive
what is a syn addition
it is addition to the same side
what is anti addition
it is an addition to opposite sides
where does the OH add to on a halohydrin reaction?
it adds to the more substituted carbon (most carbonation-like character)
what are some intermediates
carbocations, carbanions, radical, carbenes
why are reactive intermediates important
they make reactions happen
what are carbenes used for
to make cyclopropanes
why are cyclopropanes unstable
they have an angle strain (60 degrees deviation from 109.5)
torsional strain with eclipsing hydrogens
what is the charge of a carbene
it has no charge, it is neutral
what is a stereospecific reaction
it is the retention of stereochemistry
if your starting material is trans, your ending product is trans
if your starting material is cis, your ending material is cis
when we use :CH2 in a reaction, what forms and what is a stereochemical feature about it?
it forms a cyclopropane
it has stereoselectivity where the stereochemistry of the alkene is retained in the cyclopropane
what does it mean to be divalent and what is an example of it?
divalent means two bonds, carbenes are divalent, they have two bonds