Ochem reagents & reaction stereochemical outcomes Flashcards
in acid-catalyzed hydration rxn, what does catalyst do (and what is?)
Strong acid the catalyst, usually H2SO4 or something
Method of hydration with Markovnikov addition (more substituted position favored)
Rate of acid-catalyzed hydration rxn dependent on what?
structure of starting alkene, (the more substituted, the faster it go)
((which makes sense bc more stable carbocation is formed))
Where is the OH in an acid catalyzed hydration rxn?
The more substituted position
What reaction occurs with an alkene in dilute H2SO4 (and how can write that reagent?
H3O+ (goes towards OH addition from alkene)
What reaction occurs with an OH group in conc. H2SO4 (and how can write that reagent?)
E1 elimination, alkene formation
Can write H+ as reagent
Oxymercuration-Demercuation
what do, and markovnikov or anti?
(bonus for reagents)
Method to achieve markovnikov addition without carbocation rearrangement
Reagents:
1) Hg(OAc)2 , nuc (could be water)
2) NaBH4
Oxymercuration-Demercuration reagents
1) Hg(OAc)2, Nuc (could be H2O)
2) NaBH4
Hydroboration oxidation
reagents,
anti or not anti?
type of addition?
1) BH3 * THF
2) H2O2, NaOH
Anti-markovnikov
Syn addition
(no trans only cis)
Define Syn additon
only 2 of 4 possible stereoisomers formed
Catalytic Hydrogenation
reagents
anti/markovnikov
type of addition
-adding H2 across an alkene with
H2 & metal catalyst (like Pt)
-markovnikov not relevant
-syn addition
Halogenation
reagents
anti/markovnikov
type of addition
-Addition of X2 (Br2 or Cl2) across alkene
-Br2/Cl2
(if water is solvent probably get halohydrin formed instead)
-Anti
-NOT syn
Halohydrin formation
reagents
anti/markovnikov
type of addition
Br2 or Cl2
Anti
not syn
Asymmetric Catalytic Hydrogenation
H2 and Wilkonson’s catalyst
Syn I think?
Anti-Dihydroxilation:
reagents and jist
RCO3H
weird acid time, draw it real suggestive
achieves anti hydroxilation of an alkene
Syn-Dihydroxilation
reagents and jist
OsO4 (catalytic) + nuc (some reducing agent)
or
MnO4
+nuc (some reducing agent)
**dont know the last part of the mechanism yet
Ozonolysis
reagents & jist
Adding O3 across an alkene and completely cleaving the C=C bond
Reagents: O3 and DMS (mild reducing agent)
for predicting prodcuts, just draw two Os in each pi bond
Are internal or terminal alkynes generally more favored?
terminal, if it can form, it will
What increases the acidity of a terminal alkyne?
get pranks it is the terminal alkyne, very stable conj base, so very acidic H at the end there
Geminal dihalide
both Xs on same carbon atom
Vicinal dihalide
Xs on neighboring carbons
Reagent for removing two Xs and forming an alkyne
1) NaNH2 in NH3 (l)
2) H2O (serves as proton source)
need base for first deprotonation, strong base for second
Xs (Br or Cls) are removed via an E2 mechanism (so happens twice)
Catalytic hydrogenation for Alkynes
H2
Pt
goes straight to alkane like alkenes do, just happens twice
(alkyne consumes 2 equivalents of H2)
How to get cis alkene from alkyne?
Use of H2 and a poisoned catalyst like lindlar’s
What will treatment of an alkyne with
1) H2
2) Poisoned Catalyst (lindlar’s)
result in?
cis alkene
Dissolving metal reduction (hint alkynes)
reagents and results in what
alkynes to trans alkenes
1) Na
2) NH3 (l)
Reagents to make trans alkene vs cis alkene from an alkyne?
cis alkene: hydrogentation with poisoned catalyst
1) H2
2) Poisoned catalyst, Lindlar’s
trans alkene: dissolving metal reduction
1) Na
2) NH3 (l)
Hydrohalogentation of Alkynes:
it’s weird and termolecular, same mechanism for alkenes basically just simultaneous and weird
(gives two halogens on same C atom) they be throwing mad peace
Radical addition of HBr:
(to an alkyne)
results in alkene with one X
mixture of E and Z isomers
HBr
ROOR
Hydration of Alkynes
reagents and leads to what weird product situation?
1) H2SO4, H2O
2) HgSO4
leads to acid catalyzed tautomerization bc enol not stable, turns into a ketone usually but could be aldehyde
(note acid catalyzed usually done to terminal alkynes for more control of outcome products)
Keto-enol tautomerization is an ___________ process
equilibrium, but the ketone is highly favored
Hydroboration Oxidation Reagents for an Alkyne
1) not BH3 bc that would add 2 Bs
1) R2BH
2) H2O2, NaOH
Hydroboration oxidation of an alkyne results in what weird product situation?
Makes an enol which is then tautomerized under the basic conditions to usually form an aldehyde (could be a ketone)
ozonolysis of alkynes
reagents and products
1) O3
2) H2O
R-C=O and an OH on the C
+ O=C=O (CO2 formation from terminal carbon atom)
