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Chem 281 > Chem final > Flashcards

Chem final Flashcards

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1
Q

Nucleophilic substitution SN2

A
  • Nucleophile leaves as LG leaves
  • Polar aprotic solvent
  • Inversion of stereochem
  • 1>2>3
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2
Q

Nucleophilic substitution SN1

A
  • Lg leaves and carbocation forms then LG leaves
  • Racemization forms
  • 3>2>1
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3
Q

Elimination E2

A
  • Single step elimination where base removes beta hydrogen as leaving group leaves
  • Polar aprotic
  • 3>2>1
  • Heat
  • Zaitsev and Hoffman
  • If there are 2 beta hydrogens E and Z form
  • Cyclohexane must be anti elimination
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4
Q

Elimination E1

A
  • Bulkiest groups on opposite sides
  • Polar protic
  • Goes via carbocation
  • Heat
  • 3>2>1
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5
Q

Rearrangement

A

The more stable carbocation forms due to a hydride shift of methyl shift in the E1 or SN1 reaction

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6
Q

Dehydrohalogenation of alkyl halides

A
  • Elimination where H-X are removed to form a double bond
  • 2/3/VINYL/ALLYLIC go via SN1
  • 1/meth go via SN2

-Alkyl halide, base, heat

KOH/EtOH, EtONa/EtOH, t-BuOK/t-BuOH

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7
Q

Forming a terminal alkyne

A

Extra mole of NaNH2 and NH4Cl to reprotonate

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8
Q

Dehydration of alcohols

A
  • Elimination reaction where OHH are eliminated
  • Alkynes can be formed from diols
  • The lower the alcohol degree the more heat and acid needed
  • Alcohol, heat, water
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9
Q

Synthesis of alkoxides

A
  • Remove a teminal hydrogen from an alcohol with
    1) Oxidation reduction (Metalic sodium 2NA)
    2) Acid-Base (NaH)
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10
Q

Hydrogenation of alkenes/alkanes

A
  1. Heterogeneous Catalysis (Pt,PD,Ni), H2
  2. Wilkinsons catalyst (Homgeneous) , H2
  3. Ni2-B
  4. Lindlars catalyst
  5. Li, liq NH3
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11
Q

Pt, Pd, Ni, H2 heterogeneous catalysis CATALYTIC

A

Heat, Pt, PD, Ni, H2
Syn addition
Can go all the way just need more moles H2

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12
Q

Wilkinsons catalys homogeneous catalyst CATALYTIC

A

H2, Heat, Rh(PPh3)3Cl
Syn addition
Can go all the way just need more moles H2

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13
Q

Ni2B P-2 catalyst

A

Only alkyne to alkene
Syn addition
CIS ALKENE- Z alkene

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14
Q

Lindlars

A

Only alkyne to alkene
Syn addition
CIS ALKENE- Z alkene

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15
Q

Liq, Nh3, LI radical mechanism

A

Only alkyne to alkene
Anti addition
TRANS ALKENE- E alkene

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16
Q

How to make a geminal dihalide

A

R-C(db)O-CH3 and PCL5 at 0 degrees

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17
Q

How to synthesize an alkene from Vicinal and geminal dihalides

A

Both use 2 moles of NaNH2 and heat

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18
Q

How to make acetylide anion

A

React an alkyne with NaNH2 and heat, this can be reacted with R-X to make new alkynes

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19
Q

Electrophilic addition of hydrogen halides

A

Addition of H-X across a double bond
Goes through a free carbocation intermediate
Produces a racemic mixture if stereochem is involved
Markovnikov addition

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20
Q

How do you favour zaitevs or hoffman product

A

Use a small strong base for zaitev

Use a bulky strong base for hoffman

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21
Q

H-Br and RO-OR

A

Antimarkovnikov addition of HBR when peroxides are present

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22
Q

Acid-catalyzed dehydration

A

Strong acid and water, Stong acid donates a hydrogen to water and the water donates a H then attacks

Markovnikov regioselective

Carbocation intermediate

Rearrangements can occur

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23
Q

3 ways to add water

A

Acid-catalyzed-Markovnikov-No stereo
Oxymercuration-Demercuration-Markovnikov-No stero
Hydroboration oxidation-Anti markovnikov-Syn addition

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24
Q

Oxymercuration-demercuration

A

2 step process

  1. Hg(OAc) Thf-H20
  2. Nabh4

First step adds OH and HG complex

Second stem switches HG and H

Markovnikov regioselective

No carbocation

Oxymercuratin is Anti

Demercuration creates a mix of syn and anti

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25
Q

Hydroboration-Oxidation

A

2 steps
1.Bh3-thf
H and BH2 add

  1. H202 NaOH
    OH adds where BH2 was

Anti markovnikov

Syn addition

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26
Q

What is hydroboration

A

An alkyl borane adds to a carbon and a hydrogen

BH3 adds an H to one and BH2 to another in anti markovnikov fashion and syn

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27
Q

How do you make trialkyl borane

A

Add 3 frowning faces to BH3

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28
Q

How do you oxidize trialkyl borane?

A

React it with 3 counts of H202

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29
Q

How do you hydrolyze trialkyl borane?

A

React it with NaOH and H20 leads to 3 alcohols and Na3 BO3

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30
Q

What are the 3 parts of

Hydroboration oxidation hydrolysis

A
  1. BH3 and THF This adds to the alkene anti
  2. Oxidation (H202)
  3. Hydrolysis (NaOH, H2O)
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31
Q

What can be said about the regioisomers that oxymerc-demerc and hydrobor-oxidation produce

A

They are opposites

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32
Q

What is hydroboration protonolysis of alkylboranes

A

Alkylborane reacting with CH3CO2H and heat to produce and alkane they literally switch

Syn addition

Enantiomer also there

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33
Q

What can be used instead of H in CH3CO2H in hydroboration-protonolysis?

A

A d or t can replace the H.
These are deuterium or tetrium

Deuterium is H with 2 neutrons
Tetrium is H with 3 neutrons

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34
Q

Electrophilic addition of X2 (CL2 and BR2)

A

Produces a racemic mixture

X bonds in syn and then another x comes and attacks the carbon breaking the bond and forming the vicinal dihalide

The other X attacks via SN2

Temporary ring forms

Anti stereoselective

Enantiomers

Attacks from the opposite face of the original X

35
Q

What forms when X2 attacks a and both carbons of the db have the same substituents?

A

A meso compound forms

36
Q

What happens when X2 is added to a trans and cis compound?

A

Trans-Meso

Cis-Enantiomers

37
Q

Halohydrin formation

A

Addition of OH and X across a double bond

Markovnikov

X2 and H20

X forms a ring system and H20 breaks it

Anti regioselective

38
Q

Halohydrin with ROH

A

If h20 is replaced by ROH in a halohydrin reaction then an ether and x form

Anti regioselective

39
Q

What is dihydroxylation of an alkene?

A

2OH groups added to adjacent carbons ie a diol is formed

40
Q

What are the 2 ways for syn dihydroxylation of vicinal carbons

A
  1. Dilute KMNO4, NaOH, H20 and the cold

2. OSO4, pyridine then H20 and NaHS03

41
Q

What happens during syn dihydroxylation?

A
  1. The complex forms

2. The complex is removed and a cis diol is formed

42
Q

What gives a better yield out of the 2 mechanisms for syn dihydroxylation and why?

A

OSO4 one because KMNO4 runs the risk of over oxidyzing but OSO4 is extremely toxic

43
Q

What is oxidative cleavage of a double bond

A

An O is added to both sides of a double bond, ketones, carboxylic acids, aldehydes may form

44
Q

What is cleavage with Hot permanganate

A

KMnO4, NaOH, H20 and heat then H30+ will cleave a double bond

45
Q

What forms:

Co2,
Carboxylic acid
Ketone

IN CLEAVAGE

A

CO2-C with 2 H
Carboxylic acid- C with 1 H
Ketone- C with 0 H

46
Q

What will do oxidation without cleavage?

A

OSO4 and the heat

47
Q

What will cleave

A

KMNO4

48
Q

What are 2 ways to make epoxides?

A
  1. MCPBA
    or
  2. Halohydrin and base
49
Q

What are the 2 possibilities when O3 cleaves a double bond

A
  1. It always cleaves to ketones then more may happen
    A) A strong oxidative agent finishes the job and create co2, carboxylic acids, ketones
    B) A strong reducing agent stops it there
    create _____, aldehydes, ketones
50
Q

What is an aldehyde

A

RdbOC CH3

51
Q

What will strong cleavage with KMNO4 result in

A

Ketones, carboxylic acids and co2

52
Q

What are strong oxidative and what are strong reducing agents?

A

Ox-

Red-ME2S OR Zn, AcOH

53
Q

Electrophillic addition of Cl2, I2, or Br2

A

X2 in excess over CH2CL2
Transforms an alkyne to a dual geminal dihalide

Anti addition

54
Q

Addition of hydrogen halides to alkynes

A

Adding H-X in excess produces geminal dihalide

Markovnikov regioselective

55
Q

What happens when cleaving alkynes?

A

O2H gets added to both sides of the bond, even with a strong oxidizing agent (KMNO4)

Addition of 2 O groups to the carbon

CARBOXYLIC ACIDS

56
Q

Compare ethers and alcohols

A

Similar solubility in water, alcohol much higher bp and melting point

57
Q

What are the 3 ways to convert alcohols to alkyl halides?

A
  1. H-X
  2. SOCl2
  3. PBr3
58
Q

How do you turn an alcohol to an alkyl halide?

A

Add R-OH with H-X to get R-X and H20

59
Q

What alcohols are the most reactive

A

3>2>1

60
Q

What is the ranking of reactivities with alcohols?

A

I>Br>Cl

61
Q

What 2 things can convert Alcohols to alkyl halides and what conditions must be met?

A

1.H-X
or
2. Na-X acid catalyzed

62
Q

What path do 3,2, benxyllic, allylic alcohols take?

A

SN1

63
Q

What path do 1 and meth alcohols take?

A

SN2

64
Q

What does PB3 do?

A

It converts 1 AND 2 alcohols to alkyl halides
COLD prevents rearrangement
PBr2 bonds the alcohol
Then the other Br attacks via SN2

65
Q

What does SOCL2 do?

A

It converts 1 and 2 alcohols to alkyl halides
COLD prevents rearrangement
Pyridine catalyzes

66
Q

What are 3 good leaving groups for alcohols?

A

Ms, Ts, Trifate…OH is a bad leaving group so this helps with SN2
Pyridine catalyzes
Stereochem is retained

67
Q

What are the 3 ways to make ethers?

A
  1. Intermolecular dehydration-Only good for symmetrical
  2. Williamson ether synthesis
  3. Alkoxymercuration-demercuration
68
Q

What is acid catalyzed dehydration of ethers?

A
  1. 2 primary or secondary alcohols combine to make an ether,
    The acid makes a good LG then the other ether comes and attaches then water deprotonates it
69
Q

What is the exception to acid catalyzed dehydration to form ethers?

A

Acid can catalyze a reaction between a primary or primary alcohol and a tertiary

The acid removes the OH group from the tertiary alcohol then the other alcohol attacks and bonds

70
Q

What do unsymmetrical primary alcohols result in?

A

A mixture of 3 ethers

71
Q

What is the williamson ether synthesis?

A

An alkoxide substitutes onto an alkyl halide and forms and ether via SN2

The alkoxide can be 1 2 or 3

The alkyl halide must be primary

An ether in a ring can be formed by deprotonation of the OH group

An epoxide can be formed in a ring from adjacent OH group and X in trans configuration, a base removes the H then the O attacks SN2 and forms an epoxide

Only trans works not cis to form an epoxide

72
Q

What is formed from Alkoxymercuration-demercuration

A

An ether that is markovnikov regioselective

73
Q

What are the 2 types of protecting groups and what are they used for?

A
  1. T-butyl ethers protecting grouo
  2. Silyl ether protecting group SILICON

Used for protecting a primary alcohol while a reaction is going on in a different part of the molecule

For t butyl Isobutene must be used

For siylyl any si compound

74
Q

How are tbutyl added?
How are siyly ether added?
How are they each removed?

A

Tbutyl added with H2SO4, removed with dilute aqueous acid (H+,H20)

Silyl ether (TBSCL) added by imidazole and DMF , Removed by fluorine compound (exBu4FN and THF)

75
Q

When must protecting groups be used?

A

When were trying to add a gringard reagant or any negative species

76
Q

What is TBSCL or TBDMSCL

A

Silyl protecting groups

77
Q

What are some of the only things ethers react with and what do they form

A

Acids and this forms salts

78
Q

How can you for 2 alkyl halides from an alkyl halide?

A

Treat with strong acid, HBr, H2SO4, HI

79
Q

What is electrophillic epoxidation?

A

Alkene with MCPBA, or a Peracetic acid (Extra O)

The more substituted db forms the epoxide

Syn addition

Trans and Cis are retained

80
Q

Acid-catalyzed epoxide opening

A

Epoxide and acid react to form a trans diol

Acid attacks the more substituted side

Anti addition

81
Q

Base-catalyzed epoxide opening

A

Epoxide and base react to form ether and alcohol

Base attacks the less substituted side

Anti addition

82
Q

What is a pronated epoxide similar to?

A

A 3 carbocation

83
Q

What are the ways to make cis and trans 1,2 diols via alkenes then epoxides?

A

Cis-Cold kmno4 reaction
or
OSO4 reaction

Both do syn dihidroxylation

Trans-MCPBA then acid opening

Chem 281 (2 decks)

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