Ochem reagents & reaction stereochemical outcomes

Question 1

in acid-catalyzed hydration rxn, what does catalyst do (and what is?)

Answer 1

Strong acid the catalyst, usually H2SO4 or something

Method of hydration with Markovnikov addition (more substituted position favored)

Question 2

Rate of acid-catalyzed hydration rxn dependent on what?

Answer 2

structure of starting alkene, (the more substituted, the faster it go)

((which makes sense bc more stable carbocation is formed))

Question 3

Where is the OH in an acid catalyzed hydration rxn?

Answer 3

The more substituted position

Question 4

What reaction occurs with an alkene in dilute H2SO4 (and how can write that reagent?

Answer 4

H3O+ (goes towards OH addition from alkene)

Question 5

What reaction occurs with an OH group in conc. H2SO4 (and how can write that reagent?)

Answer 5

E1 elimination, alkene formation

Can write H+ as reagent

Question 6

Oxymercuration-Demercuation

what do, and markovnikov or anti?

(bonus for reagents)

Answer 6

Method to achieve markovnikov addition without carbocation rearrangement

Reagents:
1) Hg(OAc)2 , nuc (could be water)
2) NaBH4

Question 7

Oxymercuration-Demercuration reagents

Answer 7

1) Hg(OAc)2, Nuc (could be H2O)
2) NaBH4

Question 8

Hydroboration oxidation

reagents,
anti or not anti?
type of addition?

Answer 8

1) BH3 * THF
2) H2O2, NaOH

Anti-markovnikov

Syn addition

(no trans only cis)

Question 9

Define Syn additon

Answer 9

only 2 of 4 possible stereoisomers formed

Question 10

Catalytic Hydrogenation

reagents

anti/markovnikov

type of addition

Answer 10

-adding H2 across an alkene with

H2 & metal catalyst (like Pt)
-markovnikov not relevant

-syn addition

Question 11

Halogenation

reagents

anti/markovnikov

type of addition

Answer 11

-Addition of X2 (Br2 or Cl2) across alkene

-Br2/Cl2
(if water is solvent probably get halohydrin formed instead)

-Anti

-NOT syn

Question 12

Halohydrin formation

reagents
anti/markovnikov

type of addition

Answer 12

Br2 or Cl2

Anti

not syn

Question 13

Asymmetric Catalytic Hydrogenation

Answer 13

H2 and Wilkonson’s catalyst

Syn I think?

Question 14

Anti-Dihydroxilation:

reagents and jist

Answer 14

RCO3H

weird acid time, draw it real suggestive

achieves anti hydroxilation of an alkene

Question 15

Syn-Dihydroxilation

reagents and jist

Answer 15

OsO4 (catalytic) + nuc (some reducing agent)
or
MnO4
+nuc (some reducing agent)

**dont know the last part of the mechanism yet

Question 16

Ozonolysis

reagents & jist

Answer 16

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

Question 17

Are internal or terminal alkynes generally more favored?

Answer 17

terminal, if it can form, it will

Question 18

What increases the acidity of a terminal alkyne?

Answer 18

get pranks it is the terminal alkyne, very stable conj base, so very acidic H at the end there

Question 19

Geminal dihalide

Answer 19

both Xs on same carbon atom

Question 20

Vicinal dihalide

Answer 20

Xs on neighboring carbons

Question 21

Reagent for removing two Xs and forming an alkyne

Answer 21

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)

Question 22

Catalytic hydrogenation for Alkynes

Answer 22

H2
Pt

goes straight to alkane like alkenes do, just happens twice
(alkyne consumes 2 equivalents of H2)

Question 23

How to get cis alkene from alkyne?

Answer 23

Use of H2 and a poisoned catalyst like lindlar’s

Question 24

What will treatment of an alkyne with
1) H2
2) Poisoned Catalyst (lindlar’s)

result in?

Answer 24

cis alkene

Question 25

Dissolving metal reduction (hint alkynes)

reagents and results in what

Answer 25

alkynes to trans alkenes
1) Na
2) NH3 (l)

Question 26

Reagents to make trans alkene vs cis alkene from an alkyne?

Answer 26

cis alkene: hydrogentation with poisoned catalyst
1) H2
2) Poisoned catalyst, Lindlar’s

trans alkene: dissolving metal reduction
1) Na
2) NH3 (l)

Question 27

Hydrohalogentation of Alkynes:

Answer 27

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

Question 28

Radical addition of HBr:
(to an alkyne)

Answer 28

results in alkene with one X

mixture of E and Z isomers

HBr
ROOR

Question 29

Hydration of Alkynes

reagents and leads to what weird product situation?

Answer 29

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)

Question 30

Keto-enol tautomerization is an ___________ process

Answer 30

equilibrium, but the ketone is highly favored

Question 31

Hydroboration Oxidation Reagents for an Alkyne

Answer 31

1) not BH3 bc that would add 2 Bs
1) R2BH
2) H2O2, NaOH

Question 32

Hydroboration oxidation of an alkyne results in what weird product situation?

Answer 32

Makes an enol which is then tautomerized under the basic conditions to usually form an aldehyde (could be a ketone)

Question 33

ozonolysis of alkynes

reagents and products

Answer 33

1) O3
2) H2O

R-C=O and an OH on the C
+ O=C=O (CO2 formation from terminal carbon atom)