Alkene/Alkyne Flashcards
What did you add?
haloacid
What is your intermediate, if any?
carbocation*
* rearrangement possible
What do you get?
alkane with X and H trans
Where do the groups attach?
X more substituted
What is your stereochemistry, if any?
two stereoisomers
mnemonic for alkene + HX → alkane
What did you add?
haloacid
How much did you add?
two molar equivalents
What do you get?
alkane with more substituted geminal dihalides
Can you turn this into a vicinal dihalide with one reactant?
no
Does this rearrange?
no: vinyl* cation formed
* charge on alkene carbon
What is/are the intermediate(s), if any?
Where do the groups attach?
X on more substituted C
What is your stereochemistry, if any?
none: this is not a stereocenter
What did you add?
HBr in peroxides
What peroxides might you add?
H2O2
H3CO-OCH3
What are your intermediate(s), if any?
radical* on carbon
*no rearrangement
You want a more substituted alkyl halide.
What can you add?
HX
You want a less substituted alkyl halide.
What can you add?
HBr in H2O2
What do you get?
less substituted bromide
What is your stereochemistry, if any?
2 stereoisomers: radical is planar, so you get a mixture
What do you add?
HBr in peroxides
How much do you add?
2 molar equivalents to get alkane
What do you get?
alkane with less substituted geminal dibromide
What are your intermediates, if any?
none: vinyl carbocation, no rearrangement
What is the net reaction?
addition of geminal H and geminal Br
Where do the substituents attach?
geminal Br on less substituted C
You want the more substituted product, a dibromide.
What is your reagent?
HBr
You want the less substituted product, a dibromide.
What is your reagent?
HBr in peroxides
What reagent do you use?
KOH in ethanol (dehydrohalogenation)
What is your mechanism to make this alkene?
removal of H and Br, which must be anti
What is your mechanism to make this alkene?
removal of H and Br, which must be anti
How many steps are there?
two
What do you add?
- KOH in ethanol
- molten KOH
for internal alkyne
What do you get?
internal alkyne
What reactant(s) do you need?
- 3NaNH2 in liquid NH3
- H2O
for terminal alkyne
- termiNNNal*
- 3 bonds, 3 molar equivalents, 3 Ns in first step*
How many steps are there?
two
You want the internal alkyne.
What reagents do you use
- KOH in ethanol
- molten KOH
You want the terminal alkyne.
What reagents do you use?
- 3NaNH2 in liquid NH3
- H2O
- termiNNNal*
- 3 bonds, 3 molar equivalents, 3 Ns in first step*
Can you make a specific internal alkyne?
no: double bond can go on either side of geminal bromides
Can you make a specific internal alkyne?
yes: double bond only goes between the vicinal bromides
How much reagent do you need?
two: only need two to make an internal alkyne
What do you add?
H2SO4 in H2O
What is your major product?
more substituted alcohol
Is there a minor product?
yes: some alcohols may attach to the less substituted side, and the mixture influenced by stability of chair conformations
Where does the alcohol attach?
more substituted side (for the major product)
Can you get rearrangement in this reaction?
yes: a carbocation forms, so a hydride or methyl may rearrange from a more substituted neighbor
What is your product?
more substituted alcohol
What did you add?
- Hg(OAc)2 in H2O
- NaBH4 in NaOH
Mercury nabs water now
What is the net reaction?
alcohol adds to more substituted C, H to less substituted
Can you have rearrangement here?
no: mercury bridge prevents carbocation from forming, and no carbocation, no rearrangement
What product(s) do you get?
enol & one ketone (much more ketone)
What do you add?
- HgSO4
- H2SO4 in H2O
Where does the alcohol form?
the more substituted carbon
(and the ketone follows)
What is the net reaction?
addition of alcohol and H
What did you add?
- BH3 in THF
- H2O2 in NaOH
Bored healing triplets with the healing feet use hydrogen peroxide now.
What do you get?
less substituted alcohol
What is your net reaction?
Syn addition of less sub alcohol, and H
Do you get stereoisomers?
yes
What did you add?
- SiaBH
- H2O2 in NaOH
What product(s) do you get?
tautomerization of aldehyde and enol
What is your net reaction?
syn addition of less substituted alcohol (and H)
THEN
terminal aldehyde
Sia sings out about outside aldehydes.
What is your major product?
aldehyde from terminal alkyne
What did you add?
ICl (iodinium chloride)
What is your net reaction?
anti addition of I and Cl
Where does each group go?
I goes on less substituted C
Cl goes on more substituted C
Do you get stereoisomers?
no
What did you add?
Br2
What do you get?
vicinal dibromide
What is your intermediate, if any?
bromonium bridge
What is the net reaction?
anti addition of two Br
What do you get?
alkane tetrabromide
What do you get?
alkene vicinal dibromide
What is your intermediate, if any?
vinyl cation*
* no rearrangement
What is your net reaction?
addition of two Br
What stereoisomers do you get, if any?
trans/Z or cis/E isomers
What did you add?
Br2 in H2O
What do you get?
anti addition of Br and H (halohydrin)
Where do the groups attach?
Br is on less substituted and alcohol is on more substituted
Which reagent makes one versus the other?
top:
Br2 in H2O makes the halohydrin
bottom:
Br2 by itself makes the vicinal dibromide
What did you add?
H2 and
Pd or Pt or Ni catalyst
What is the net reaction?
syn addition of H and H
What stereoisomers can you expect, if any?
two stereoisomers
What else does this reaction need?
Pd or Pt or Ni catalyst
What influences the product ratio?
- relative stability
- steric hindrance
What did you add?
2H2 and
Pd or Pt or Ni catalyst
What do you get?
corresponding alkane
What did you add?
H2 and
Lindlar’s catalyst (quinoline)
What do you get?
cis/Z alkene
What is the net reaction?
syn addition of H and H
What did you add?
Li or Na in
liquid NH3
Give Li / Na Lamont lithium after Don dunked her in ammonia.
What do you get?
trans/Z alkene
What is the net reaction?
trans addition of H & H
What did you add?
- cold dilute KMnO4
H2O, NaOH - H3O+
OR
- OsO4 in pyridine
- NaSO3 or NaHSO3
in H2O
P&P twins drink cold shots. Water —NaOTt! After vomiting up acid, they get their keys.
What do you get?
syn diols
P&P twins drink cold shots. Water —NaOTt! After vomiting up acid, they get their keys.
What is your net reaction?
syn addition of two alcohols
“One cold shot of water and SOD-dy PER-fume.” “I’ll have the same.” Same drink order.
Where do the groups add?
additions are syn
“One cold shot of water and SOD-dy PER-fume.” “I’ll have the same.” Same drink order.
What did you add?
- cold dilute KMnO4
H2O, NaOH - H3O+
P&P twins drink cold shots. Water —NaOTt! After vomiting up acid, they get their keys.
What do you get?
- tetra-ol*
- diketone
*tetra-ol is not isolated: immediately turns into diketone from the acid in step 2
What is your net reaction?
four alcohols added across triple bond
What did you add in step 1?
peracid
Pear-shaped kitten hanging in there!
(eg. MCBPA, peracetic acid, trifluoroperacetic acid)
What did you add in this step?
H3O+
What are your intermediates, if any?
epoxide (ether bridge)
What is your stereochemistry, if any?
two stereoisomers
You want an epoxide.
What do you add?
peracid
(eg. MCBPA, peracetic acid, trifluoroperacetic acid)
You want anti alcohols.
What do you add?
- peracid (eg. MCPBA)
- H3O+
You want syn alcohols.
What do you add?
- cold dilute KMnO4
H2O, NaOH - H3O+
OR
- OsO4 in pyridine
- NaSO3 or NaHSO3
in H2O
(drunk twins lean one one another while vomiting)
What did you add?
- hot, concentrated KMnO4,
H2O, NaOH - H3O+
What do you get?
- ketone
- aldehyde → carboxylic acid
(conversion through further oxidation)
You add the following:
- hot, concentrated KMnO4,
H2O, NaOH - H3O+
Do you get bubbles?
yes: bubbles come from terminal* alkenes with these reactants
*exhaust has to go out
You add the following:
- hot, concentrated KMnO4,
H2O, NaOH - H3O+
Do you get bubbles?
no: bubbles come from terminal* alkenes with these reactants
*exhaust has to go out
What did you add?
- hot, concentrated KMnO4,
H2O, NaOH - H3O+
OR
- O3
- H2O
(same products with alkynes)
You add
- hot, concentrated KMnO4,
H2O, NaOH - H3O+
Are there bubbles?
yes: bubbles can be expected from terminal alkynes
You add
- O3
- H2O
Are there bubbles?
yes: bubbles can be expected from terminal alkynes
Terminal alkynes blow bubbles out
(3Bs in bubbles + 3 bonds in alkyne)
Will there be bubbles?
no: internal alkynes produce no bubbles
Will there be bubbles?
no: internal alkynes produce no bubbles
There are no bubbles.
What did you add?
- O3
- H2O
ozonolysis produces no bubbles for terminal alkenes
fThere are no bubbles.
What did you add?
- hot, concentrated KMnO4,
H2O, NaOH - H3O+
OR
- O3
- H2O
internal alkenes won’t produce bubbles in either case
