Ch 6: Reactions of Alkenes- Mechanisms Flashcards
Is the halogenation reaction (addition of HX) Markovnikov?
YES; X will attach to the more substituted side
What does the two step mechanism for the halogenation reaction involve?
Initial protonation of the alkene pi bond to form a carbocation, which reacts with X- to give the product haloalkane
Water, in the presence of ___, converts an alkene into ____.
an acid catalyst; an alcohol
What does the acid-catalyzed hydration mechanism involve?
initial protonation of the alkene pi bond to give a carbocation, which reacts with the nucleophile water to create a second intermediate, which loses a proton to give the alcohol product.
Is the acid-catalyzed hydration reaction Markovnikov?
YES; the OH group becomes bonded to the more highly substituted carbon
Cl2 or Br2 is used to convert an alkene into a ____.
vicinal dihalide
What does the addition of molecular bromine/chlroine involve?
attack by the alkene pi bond on one atom of X2 to give a bridged halonium ion intermediate that is attacked by X- from the backside to give the vicinal dihalide
The addition of bromine and chlorine displays ___ stereoselectivity because of the___ and ___.
anti addition; the halonium ion intermediate; Z alkenes give different products than E alkenes
What does the halohydrin formation mechanism (addition of HOCl and HOBr involve?
attack by the alkene pi bond on one atom of X2to give a bridged halonium ion intermediate that is attacked by H2O from the backside to give a new intermeidate, which loses a proton to give the halohydrin.
Are carbocation rearrangements possible for a halogenation reaction?
YES
Are carbocation rearrangements possible for an acid-catalyzed hydration reaction?
YES!
Are carbocation rearrangements possible for the addition of bromine/chlorine?
NO
Are carbocation rearrangements possible for the halohydrin reaction?
NOOOPE NOPE NOPE
