ethers, epoxides, sulfides, aldehyes, ketones

Question 1

What is the oxygen hybridization in an ether?

Answer 1

Sp3

Question 2

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

Answer 2

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

Question 3

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

Answer 3

In the sp3 orbital

Question 4

Why are ethers good solvents?

Answer 4

Their polarity and low reactivity, no H bonding is possible

Question 5

What other compound are ether boiling points similar to?

Answer 5

Alkanes due to their inability to form hydrogen bonds

Question 6

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

Answer 6

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

Question 7

How do you prepare an alkoxide?

Answer 7

Alcohol treated with Na, K, or NaH

Question 8

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

Answer 8

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

Question 9

Are ethers reactive?

Answer 9

No, stable to reagents making them good solvents

Question 10

What are cleavage reactions? What are the conditions?

Answer 10

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

Question 11

Why do we use excess HX in cleavage reactions?

Answer 11

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

Question 12

What occurs in reactions of epoxides?

Answer 12

Very reactive towards nucleophile, opening epoxied relives ring strain

Question 13

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

Answer 13

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

Question 14

Under what conditions do reactions of epoxides occur?

Answer 14

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

Question 15

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

Answer 15

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

Question 16

What are the conditions for a ring opening epoxide reaction?

Answer 16

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

Question 17

What are good nucleophile for ring opening reactions of epoxides?

Answer 17

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

Question 18

What are the conditions for an acid catalyzed ring openings?

Answer 18

Reactants: epoxides
Conditions: H2SO4| EtOH
Product: alcohol

Question 19

How do you make oxygen a good leaving group?

Answer 19

Protinate it

Question 20

How do you prepare alkyl sulfonates?

Answer 20

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

Question 21

What are 4 reactions to make aldehydes and ketones?

Answer 21

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

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

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

Answer 24

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

Question 25

What is the relative stability of aldehydes and ketones?

Answer 25

(Most stable) ketone > aldehyde > formaldehyde

Question 26

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

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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

Question 30

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

Answer 30

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

Question 31

What are the reaction conditions for cyanohydrin formation?

Answer 31

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

Question 32

What is the special condition regarding aldehyde and ketone reactions?

Answer 32

They go both ways

Question 33

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

Answer 33

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

Question 34

Reaction conditions to form intramolecular hemiacteal?

Answer 34

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

Question 35

Reaction conditions to form cyclic acetals?

Answer 35

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

Question 36

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

Answer 36

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

Question 37

What are the reaction conditions to “deprotecting” synthesis?

Answer 37

H2O, HCl

Question 38

What are the reaction conditions for imine formation?

Answer 38

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

Question 39

Reaction conditions to form enamine?

Answer 39

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

Question 40

What are the conditions for the witting reactions?

Answer 40

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

Question 41

Reaction conditions for ylide preparation

Answer 41

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