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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
Hydroboration-Oxidation
2 steps 1.Bh3-thf H and BH2 add 2. H202 NaOH OH adds where BH2 was Anti markovnikov Syn addition
26
What is hydroboration
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
27
How do you make trialkyl borane
Add 3 frowning faces to BH3
28
How do you oxidize trialkyl borane?
React it with 3 counts of H202
29
How do you hydrolyze trialkyl borane?
React it with NaOH and H20 leads to 3 alcohols and Na3 BO3
30
What are the 3 parts of Hydroboration oxidation hydrolysis
1. BH3 and THF This adds to the alkene anti 2. Oxidation (H202) 3. Hydrolysis (NaOH, H2O)
31
What can be said about the regioisomers that oxymerc-demerc and hydrobor-oxidation produce
They are opposites
32
What is hydroboration protonolysis of alkylboranes
Alkylborane reacting with CH3CO2H and heat to produce and alkane they literally switch Syn addition Enantiomer also there
33
What can be used instead of H in CH3CO2H in hydroboration-protonolysis?
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
34
Electrophilic addition of X2 (CL2 and BR2)
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
What forms when X2 attacks a and both carbons of the db have the same substituents?
A meso compound forms
36
What happens when X2 is added to a trans and cis compound?
Trans-Meso | Cis-Enantiomers
37
Halohydrin formation
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
Halohydrin with ROH
If h20 is replaced by ROH in a halohydrin reaction then an ether and x form Anti regioselective
39
What is dihydroxylation of an alkene?
2OH groups added to adjacent carbons ie a diol is formed
40
What are the 2 ways for syn dihydroxylation of vicinal carbons
1. Dilute KMNO4, NaOH, H20 and the cold | 2. OSO4, pyridine then H20 and NaHS03
41
What happens during syn dihydroxylation?
1. The complex forms | 2. The complex is removed and a cis diol is formed
42
What gives a better yield out of the 2 mechanisms for syn dihydroxylation and why?
OSO4 one because KMNO4 runs the risk of over oxidyzing but OSO4 is extremely toxic
43
What is oxidative cleavage of a double bond
An O is added to both sides of a double bond, ketones, carboxylic acids, aldehydes may form
44
What is cleavage with Hot permanganate
KMnO4, NaOH, H20 and heat then H30+ will cleave a double bond
45
What forms: Co2, Carboxylic acid Ketone IN CLEAVAGE
CO2-C with 2 H Carboxylic acid- C with 1 H Ketone- C with 0 H
46
What will do oxidation without cleavage?
OSO4 and the heat
47
What will cleave
KMNO4
48
What are 2 ways to make epoxides?
1. MCPBA or 2. Halohydrin and base
49
What are the 2 possibilities when O3 cleaves a double bond
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
What is an aldehyde
RdbOC CH3
51
What will strong cleavage with KMNO4 result in
Ketones, carboxylic acids and co2
52
What are strong oxidative and what are strong reducing agents?
Ox- | Red-ME2S OR Zn, AcOH
53
Electrophillic addition of Cl2, I2, or Br2
X2 in excess over CH2CL2 Transforms an alkyne to a dual geminal dihalide Anti addition
54
Addition of hydrogen halides to alkynes
Adding H-X in excess produces geminal dihalide Markovnikov regioselective
55
What happens when cleaving alkynes?
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
Compare ethers and alcohols
Similar solubility in water, alcohol much higher bp and melting point
57
What are the 3 ways to convert alcohols to alkyl halides?
1. H-X 2. SOCl2 3. PBr3
58
How do you turn an alcohol to an alkyl halide?
Add R-OH with H-X to get R-X and H20
59
What alcohols are the most reactive
3>2>1
60
What is the ranking of reactivities with alcohols?
I>Br>Cl
61
What 2 things can convert Alcohols to alkyl halides and what conditions must be met?
1.H-X or 2. Na-X acid catalyzed
62
What path do 3,2, benxyllic, allylic alcohols take?
SN1
63
What path do 1 and meth alcohols take?
SN2
64
What does PB3 do?
It converts 1 AND 2 alcohols to alkyl halides COLD prevents rearrangement PBr2 bonds the alcohol Then the other Br attacks via SN2
65
What does SOCL2 do?
It converts 1 and 2 alcohols to alkyl halides COLD prevents rearrangement Pyridine catalyzes
66
What are 3 good leaving groups for alcohols?
Ms, Ts, Trifate...OH is a bad leaving group so this helps with SN2 Pyridine catalyzes Stereochem is retained
67
What are the 3 ways to make ethers?
1. Intermolecular dehydration-Only good for symmetrical 2. Williamson ether synthesis 3. Alkoxymercuration-demercuration
68
What is acid catalyzed dehydration of ethers?
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
What is the exception to acid catalyzed dehydration to form ethers?
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
What do unsymmetrical primary alcohols result in?
A mixture of 3 ethers
71
What is the williamson ether synthesis?
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
What is formed from Alkoxymercuration-demercuration
An ether that is markovnikov regioselective
73
What are the 2 types of protecting groups and what are they used for?
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
How are tbutyl added? How are siyly ether added? How are they each removed?
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
When must protecting groups be used?
When were trying to add a gringard reagant or any negative species
76
What is TBSCL or TBDMSCL
Silyl protecting groups
77
What are some of the only things ethers react with and what do they form
Acids and this forms salts
78
How can you for 2 alkyl halides from an alkyl halide?
Treat with strong acid, HBr, H2SO4, HI
79
What is electrophillic epoxidation?
Alkene with MCPBA, or a Peracetic acid (Extra O) The more substituted db forms the epoxide Syn addition Trans and Cis are retained
80
Acid-catalyzed epoxide opening
Epoxide and acid react to form a trans diol Acid attacks the more substituted side Anti addition
81
Base-catalyzed epoxide opening
Epoxide and base react to form ether and alcohol Base attacks the less substituted side Anti addition
82
What is a pronated epoxide similar to?
A 3 carbocation
83
What are the ways to make cis and trans 1,2 diols via alkenes then epoxides?
Cis-Cold kmno4 reaction or OSO4 reaction Both do syn dihidroxylation Trans-MCPBA then acid opening

Chem 281 (2 decks)

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