Organic Synthesis (O2)

Question 1

Reagents used for Jones Oxidation of a secondary-alcohol to a ketone?

Answer 1

Na2Cr2O7, H20 and H2SO4

Same conditions will cause oxidation of primary alcohol to carboxylic acid

Question 2

Reagents of a Baeyer-Villiger Oxidation of a ketone to an ester?

Answer 2

Any per-carboxylic acid

Question 3

Reagents of a Mitsonobu reaction (Interconversion of secondary alcohols)

Answer 3

1. PPh3 and DEAD (diethyl azodicarboxylate)
2. ANY acidic Nu-H

(Walden inversion occurs)

Question 4

Reagents of an Appel reaction

Answer 4

Ph3P and CBr4

Question 5

E or Z isomer produced by Wittig Reaction with an stable ylide? (EWG)

Answer 5

E isomer due to sterics in Z forming transition state

Question 6

E or Z isomer produced by HWE Reaction?

Answer 6

Always E due to highly stabilised transition state.

Question 7

E or Z isomer produced by Wittig Reaction with an unstable ylide? (no-EWG)

Answer 7

Z isomer due to steric hinderance in E forming transition state.

Question 8

Reagents of an Wittig reaction

Answer 8

1. Generating Phosphonium Salt:
   Haloalkane, PPh3
2. Alkene Synthesis:
   NaH (or any base), ketone

Question 9

Reagents of an Horner-Wadsworth-Emmons (HWE) reaction

Answer 9

1. Generating Phosphonate Ester:
   Halocarboxylic Acid, P(OEt)3
2. Alkene Synthesis:
   NaH (or any base), ketone

Question 10

Benefits of HWE over Wittig reaction?

Answer 10

• Stereospecific towards E-isomer.
• More reactive nucleophile allows for upto tetrasubstituted alkenes.
• Easy to remove salt by-product.

Question 11

Reagents used for dihydroxylation of an alkene?

Answer 11

OsO4, NaOH (or any base)

OR

KMnO4, NaOH

Question 12

Reagents of Lindars Catalyst hydrogenation reaction?

Answer 12

Pd/CaCO3, Pb(Oac)2

Mild conditions do not affect other functional groups and prevent over reduction into alkene.

Question 13

Stereoselectivity of Lindars Catalyst alkyne reduction?

Answer 13

Favours Z-isomer due to syn addition by the heterogenous catalyst surface.

Question 14

Reagents for the reduction of alkynes into E-alkenes?

Answer 14

Na(s) in NH3(l)

Favours E isomer as final anion assumes most stable trans geometry.

OR

LiAlH4

Question 15

Reagents of an anti-Markonikov addition/hydroboration?

Answer 15

1. BH3, THF

2. H2O2, NaOH

Question 16

Reagents for the epoxidation of an alkene?

Answer 16

Per-carboxylic acid

Question 17

Hydrogenation of alkenes to alkanes?

Answer 17

H2, Pd/C

Question 18

Reagents of an ozonolysis reaction of an alkene?

Answer 18

1. O3 (ozone duh)

2a. Me2S (making ketones)
2b. H2O2 (making carboxylic acids)
2c. NaBH4 (making primary alcohols)

Question 19

Reagents of a Diels-Alder reaction?

Answer 19

Electron-rich diene and an electron poor alkene

Question 20

Organometallic reagent used to alkylate hard electrophilic centres (e.g. C=O carbon)

Answer 20

Organolithiums (Li+Et-)

Question 21

Organometallic reagent used to alkylate soft electrophilic centres (e.g. 1, 4-conjugate addition)

Answer 21

Organocoppers or Lithium Dialkyl Cuprates

e.g. MeCu or Me2CuLi

Question 22

Reagents of a Suzuki coupling reaction?

Answer 22

Pd(PPh3)4, K2CO3, Alkyl-B(OH)2, Alkyl-Br

Question 23

Steps of a Suzuki coupling reaction?

Answer 23

1. Loss of 2PPh3 from Pd(PPh3)4
2. Oxidative addition of bromoalkane
3. Transmetallation of boronic acid alkyl group
4. Reductive elimination of coupled product

Question 24

Reagents used for Jones Oxidation of a primary-alcohol to a aldehyde?

Answer 24

Pyridinium dichromate (PDC) in DCM

usually just use Swern oxidation instead

Question 25

Reagents used for Dess-Martin Oxidation of a primary alcohols to a aldehydes?

Answer 25

DMP (Dess-Martin Periodinane) | Selective towards primary alcohols even if secondary alcohols are present

Question 26

Reagents used for Swern oxidation of primary alcohols to aldehydes? (chemical macaroni cheese)

Answer 26

(COCl)2 Oxalyl chloride, DMSO, NEt3

Question 27

Reagents used for the mild reduction of exclusively aldehydes and ketones?

Answer 27

Na(BH4) + acid workup

Question 28

Reagents for the strong reduction of most oxidised alcohol derivatives?

Answer 28

LiAlH4

Question 29

Reagents for the selective/controlled reduction of oxidised alcohol derivatives?

Answer 29

DIBAL-H (diisobutylaluminium hydride) | Adding 1 equivalent reduces once, adding more equivalents reduces further

Question 30

Reagents for the selective/exclusive reduction of carboxylic acids?

Answer 30

BH3, THF

Question 31

How to prevent overalkylation of amines?

Answer 31

Reductive amination: forming an imine by reacting amine with formaldehyde.

Question 32

Reagents for a nucleophilic substiution of alcohol group?

Answer 32

1. Tosylate or Mesylate 2. ANY nucleophile-Na (Walden invesion occurs)