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Organic Chemistry > Organic Test 3 > Flashcards

Organic Test 3 Flashcards

(59 cards)

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1
Q

Acid- Catalyzed Dehydration of an Alcohol Mechanism

A

By the E1 mechanism

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2
Q

What two different reagants can be used if you want to form an anti-diol from an alkene?

A
  1. MCPBA then H3O+
  2. CH3CO3 in water
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3
Q

Mechanism for Ionic Addition of HX to an alkene

A
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4
Q

Stability of Cis/Trans isomers

A

Trans isomers are generally more stable than the corresponding cis isomers.

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5
Q
A
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6
Q

oxymercuration-demercuration mechanism

A

**Results in a Markovnikov addition of OH and H without rearrangement. Use if you don’t want it to rearrange!

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7
Q

Free-Radical Halogenation of HBr

Result with peroxide

A

Results in an anti-markovnikov addition in the presence of peroxide

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8
Q

Platinum and H2 as reagants together do what ____

A

reduce alkene to alkane

(hydrogenation)

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9
Q

What is the mechanism for an Acid-Catalyzed opening of an Epoxide?

A
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10
Q
A
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11
Q

Mechanism for Hydroboration of an alkene

A

**anti-mark

**syn-addition

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12
Q

Alkenes as Substituents

A

alkenyl groups:

methylene

vinyl

allyl

phenyl

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13
Q

What two reagants are used for oxidative cleavage of alkenes and what is the difference between them?

A
  1. KMnO4 (warm/conc.)

harsh, can’t recover aldehydes they are further oxidized into alcohols.

  1. O3

then (CH3)2S

can recover aldehydes

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14
Q

Addition of Hydrogen Halides to Alkenes

A
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15
Q

An E2 elimination takes place on a chair confirmation only if the proton and leaving group are _____

A

transdiaxial

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16
Q

E-Z nomenclature

A

If the two first-priority atoms are together (cis) on the same side of the double bond, you have the Z isomer, from the German word zusammen, “together.”

If the two first-priority atoms are on opposite (trans) sides of the double bond, you have the E isomer, from the German word entgegen, “opposite.”

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17
Q

Equation for Elements of Unsaturation

A

=(1/2)(2C+2-H)

C= Carbon

H= Hydrogen

Double bond= 1 element of unsaturation

A ring= 1 element of unsaturation

A triple bond= 2 elements of unsaturation

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18
Q

Zaitsev’s rule (stability of double bonds)

A

More substituted double bonds are usually more stable.

The alkyl groups attached to the double bonded carbons stabilize the alkene.

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19
Q

If an alkene can not easily undergo hydration in aqueous acid, what reagant can be used?

A
  1. Hg(OAc)2/ H2O
  2. NaBH4

(oxymercuration-demercuration)

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20
Q

Energy Differences in cis-trans isomers

A

Trans isomers are generally more stable than the corresponding cis isomers. In this case, the alkyl substituents are separated farther in trans isomers than they are in cis isomers.

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21
Q

Mechanism for the formation of Halohydrins (OH and X) from alkenes

A
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22
Q

What reagants are necessary to turn a double bond into a dibromocyclopropane?

A

CHBr3

KOH

and H2O

**cis/trans isomerism retained

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23
Q

Summary for naming Alkenes

A
  1. Select the longest chain or largest ring that contains the largest possible number ofdouble bonds, and name it with the -ene suffix.
  2. Number the chain from the end closest to the double bonds. Number a ring so that the double bond is between carbons 1 and 2. Place the numbers giving the locations of the double bonds in front of the root name (old system) or in front of the suffix -ene,
    - diene, etc. (new system).
  3. Name substituent groups as in alkanes. The ethenyl group and the propenyl group are usually called the vinyl group and the allyl group, respectively.
  4. Remember E-Z Nomenclature if you can’t use Cis/Trans. (Also, never forget R/ S if necessary)

(diene,triene,tetraene,etc)

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24
Q

What is a peroxide?

25
What is the reagant necessary for catalytic hydrogenation (adding H2 across a double bond)? What is the stereochemistry?
syn-addition
26
What reagant can you use to form an acetylide ion?
NaNH2
27
Dehydrohalogenation by the E2 mechanism
Reliable if poor SN2 substrate. One step.
28
In aqueous conditions, what reagant can be used to create an epoxide?
peroxyacetic acid (CH3CO3H)
29
When an epoxide is in a solution of ____ you end up with the anti-addition of 2 OH, a diol.
H3O+ epoxides are unstable in acid conditions
30
Result of Branching on boiling point of Alkenes
increased branching lowers boiling point
31
32
Bredt's Rule
\*\* If there is a double bond at the bridgehead carbon of a bridged bicyclic system, one of the two rings contains a cis double bond and the other must contain a trans double bond. \*\*If the larger ring contains at least eight carbon atoms, than it can contain a trans double bond, and the bridgehead double bond is stable
33
What reactants allow you to debrominate vicinal dibromides
NaI/ Acetone By the E2 mechanism
34
Stereochemistry of HBr, HCl, and HI when added to an alkene
forms an alkane that follows Markovnikov's Rule. Cation forms more stable intermediate (tertiary)
35
What is formed in the simmons-smith reaction (CH2I2/ Zn(Cu))
36
Reactant used to dehydrate alcohols into alkenes
conc. H2S04/ Heat or H3PO4
37
Mechanism of Debromination of Vicinal Dibromides
38
Mechanism for the Formation of Carbenes
39
Formation of a Hofmann product
-due to steric hindrance
40
Stereochemsitry of Halogen Addition
\*\*anti-addition.
41
Acid-Catalyzed Hydration of an Alkene
\*\*Follows markovnikov's Rule
42
What do you use if you want to add H and OH across a double bond in an anti-markovnikov and syn fashion?
1. BH3THF 2. H2O2/ -OH
43
Hydration of an Alkene
44
Numbering IUPAC rules
The chain is numbered starting from the end closest to the double bond, and the double bond is given the lower number of its two double-bonded carbon atoms
45
Stereochemistry of the E2 reaction
46
Alkoxymercuration- demercuration
47
Order of reactivity of alcohol dehydrogenations
Go through the E1 mechanism tertiary\>secondary\>\> primary Rearrangements are COMMON
48
Anti-mark addition of H and Br to reduce alkene to alkane needs:
HBr and R-O-O-R (peroxide) | (\*\*Doesn't happen with HCl and HI)
49
What two different reagants can be used if you want to form a syn-diol from an alkene
1. OsO4/ H2O2 \*\*expensive/highly toxic/volatile 2. KMnO4/H20 (cold/dilute) \*\*cheap/ low yield/safer \*\*\*both are syn because the two Oxygens add at same time
50
By what mechanism can an acetylide ion create larger organic molecules?
By an SN2 mechanism Need a strong base/ good nucleophile Primary and unhindered \*\*If hindered, the acetylide ion may abstract a proton, giving an E2 mechanism.
51
52
Mechanism for Free Radical Additon of HBr to Alkenes
53
Addition of Halogens to Alkenes
54
Treat an alkene with ____ to reduce to an alkane (hydrogenation)
platinum catalyst and H2
55
Stability of Cycloalkenes 1) less than 5-membered 2) 5-membered or greater
1) less than 5-membered rings are unstable (ring strain) 2) 5-membered or greater rings are stable if cis. Trans rings must be 8-membered or larger to be stable.
56
What reagant is used to turn an alkene into an epoxide? What is the configuration?
MCPBA \*\*retains stereochemistry
57
Order of carbocation stability
58
Markovnikov's Rule
59
What reagants are necessary to turn an alkene into a halohydrin (add an X and OH?)
X2 and H2O (aqueous) \*\*anti addition \*\*markovnikov

Organic Chemistry (8 decks)

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