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ochem2 > ethers, epoxides, sulfides, aldehyes, ketones > Flashcards

ethers, epoxides, sulfides, aldehyes, ketones Flashcards

1
Q

What is the oxygen hybridization in an ether?

A

Sp3

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2
Q

What are two main differences between the bonding in ethers and alcohols?

A

C-O bond is longer in Ether and the C-O-C bond angle is greater (~112º)

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3
Q

Where are the lone pairs on the oxygen in ethers located?

A

In the sp3 orbital

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4
Q

Why are ethers good solvents?

A

Their polarity and low reactivity, no H bonding is possible

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5
Q

What other compound are ether boiling points similar to?

A

Alkanes due to their inability to form hydrogen bonds

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6
Q

What are the conditions for a Williamson ether synthesis? What are rules regarding the conditions?

A

Reactant: alkoxide RO-
Conditions R-X (must be CH3 or 1º)
Product: ether

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7
Q

How do you prepare an alkoxide?

A

Alcohol treated with Na, K, or NaH

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8
Q

What are two ways to prepare epoxides? How are they added?

A
  1. Use peroxyacid or MCPBA
  2. Use halohydrin formation (Br2, H2O) with subsequent NaOH
    Added via syn addition
    Both on alkenes
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9
Q

Are ethers reactive?

A

No, stable to reagents making them good solvents

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10
Q

What are cleavage reactions? What are the conditions?

A

Reactant: ROR’
Conditions: (xs) HX, heat
Product: Mixture of ROH, RX, R’OH, R’X

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11
Q

Why do we use excess HX in cleavage reactions?

A

To allow ROH product to from RX and not a mixture (R’X and RX)

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12
Q

What occurs in reactions of epoxides?

A

Very reactive towards nucleophile, opening epoxied relives ring strain

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13
Q

What is the reactivity of HX in cleaving reactions? What are the conditions?

A

Most acidic HI>HBr>HCl least acidic. Occur under acidic conditions

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14
Q

Under what conditions do reactions of epoxides occur?

A

Acidic, basic sometimes neutral. Will influence the side of the nucleophile attack

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15
Q

In unsymmetrical epoxides where will the nucleophile attach under acidic and basic conditions?

A

Acidic conditions: Nu attacks more hindered side
Basic conditions: Nu attacks less hindered side

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16
Q

What are the conditions for a ring opening epoxide reaction?

A

Reactant: Nucleophile
Conditions: 1. epoxide, ether 2. H3O+
Product: Alcohol (enantiomers)

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17
Q

What are good nucleophile for ring opening reactions of epoxides?

A

C,O,S,N with -OR, -SR, -CN, -CR3, -alkene, -alkyne, -H, NH3

18
Q

What are the conditions for an acid catalyzed ring openings?

A

Reactants: epoxides
Conditions: H2SO4| EtOH
Product: alcohol

19
Q

How do you make oxygen a good leaving group?

A

Protinate it

20
Q

How do you prepare alkyl sulfonates?

A

Reactants: alcohol, sulfonate
Conditions: pyridine
Product: alkyl sulfate (R-OTs group)

21
Q

What are 4 reactions to make aldehydes and ketones?

A
  1. 2ºOH to K via PCC| CH2Cl2
  2. 1ºOH to A via PCC| CH2Cl2
  3. Ozonolysis of alkene via 1.O3 2. Zn, H2O
  4. Fiedel Craft Acylation of benzene with acyl chloride or acyl anhydride
22
Q

What are the reaction conditions of gringard and organolithium to aldehyde or ketone?

A

Reactant: aldehyde or ketone
Conditions: 1. R-MgBr (R-Li), ether 2. H3O+
Products: alcohol + new R group. 1º (A) or 2º (K)

23
Q

What are the reaction conditions of an aldehyde and ketone reduction?

A

Reactants: aldehyde or ketone
Conditions: 1. LAH, ether 2. H2O or H2,Pt, NaBH4|CH3OH
Product: alcohol 1º (A) or 2º (K)

24
Q

What are the hybridizations present in carbonyl bond? Is there any resonance?

A

O and C are sp2 hybridized. Resonance is possible to create nucleophilic base of oxygen and electrophilic carbon

25
Q

What is the relative stability of aldehydes and ketones?

A

(Most stable) ketone > aldehyde > formaldehyde

26
Q

How is stability increased for carbonyl groups? How is this done?

A

Increasing the number of alkyl groups attached to the carbonyl group since they are able to donate electrons and increase stability of the C+

27
Q

What are the reaction conditions of nucleophilic addition (hydration) of aldehydes or ketones?

A

Reactants: aldehyde/ ketone and water
Conditions: acid (H3O+) or base (-H or -OH)
Products: hydrate, 2 OH on same C

28
Q

How is equilibrium determine or influenced in aldehyde and ketone reactions?

A

Carbonyl structure (electric, steric effects)
Hydrate structure (steric)

29
Q

How does carbonyl structure influence equilibrium in aldehyde and ketone reactions?

A

Alkyl groups stabilize carbon, increase R groups = decrease in C reactivity. Halogenated alkyl groups are electron withdrawing and destabilize carbonyl C which increases reactivity

30
Q

How does hydrate structure influence equilibrium in aldehyde and ketone reactions?

A

Increasing size of alkyl groups = decrease in stability of hydrate due to steric crowding = not formed easily = decreased reactivity of C

31
Q

What are the reaction conditions for cyanohydrin formation?

A

Reactants: aldehyde and ketone
Conditions: NaCN (KCN)| H2O, H2SO4 or KCl
Product: cyanohydrin (OH and CN on same group)

32
Q

What is the special condition regarding aldehyde and ketone reactions?

A

They go both ways

33
Q

What are the reaction conditions to go from aldehyde/ketone to acetal?

A

Reactant: aldehyde/ ketone
Conditions: 2 eq of R-OH, H+
Products: acetal
Forms hemiacetal intermediate

34
Q

Reaction conditions to form intramolecular hemiacteal?

A

H+. O from C=O bonds to H to form OH then OH from aldehyde/ketone bonds to C+

35
Q

Reaction conditions to form cyclic acetals?

A

Reactant: aldehyde/ketone
Conditions: ethane-1,2 diol|TsOH, benzene
Product: cyclic acetal
*Adds two C

36
Q

Why would you use ethane diol and tosic acid in synthesis?

A

Can be used as a protecting group of aldehyde and make it un reactive to bases and nucleophile

37
Q

What are the reaction conditions to “deprotecting” synthesis?

A

H2O, HCl

38
Q

What are the reaction conditions for imine formation?

A

Reactant: aldehyde/ketone
Conditions: R-NH3 or NH3
Product: imine (C=N-R)
*forms hemiaminal intermediate

39
Q

Reaction conditions to form enamine?

A

Reactant: aldehyde/ketone
Conditions: 2º amine (R2NH)
Product: enamine ( has C=C and C-NR)
*has hemiaminal intermediate

40
Q

What are the conditions for the witting reactions?

A

Reactant: ylide + aldehyde/ketone
Conditions: none
Product: Alkene between C=P of ylide and C=O of aldehyde/ketone

41
Q

Reaction conditions for ylide preparation

A

Reactant: PhP: + alkyl halide (1º or 2º)
Conditions: n-BuLi, ether
Product: ylide

ochem2 (13 decks)

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