Synthesis of Alcohols

Question 1

oxidation reduction memory aid

Answer 1

LEO lion goes GER

loss of e- = oxidation

gain of e- = reduction

Question 2

oxidation definition

Answer 2

lost e-

gained bonds to O

lost bonds to H

Question 3

reduction definition

Answer 3

gained e-

lost bonds to O

gained bonds to H

Question 4

Sn1/Sn2

Answer 4

CH3, 1°, 2° substrate RX + OH- —> ROH (Sn2)

2°, 3° substrate RX + H2O —> ROH (Sn1)

Question 5

problems synthesizing alcohols

Answer 5

RX are typically synthesized from alcohols

elimination reactions compete

carbocation rearrangement

Question 6

indirect method of synthesis

Answer 6

Nu = acetate ion (fair, weakly basic)

forms ester, hydrolosys, get alcohol

Question 7

catalytic hydrogenation

Answer 7

Syn addition of H2 (same side)

Catalyzed by Pd, Pt, Ni

Not selective

Question 8

Problems with catalytic hydrogenation

Answer 8

also reduces c=c, alkyne, c=o (ketone, aldehyde)

Racemic mixture

Question 9

Hydrides

Answer 9

Strong base/Nu

Attached to B/Al to reduce basicity

Question 10

NaBH4 reduces…

Answer 10

Reduces aldehyde –> 1°

Reduces ketone –> 2°

No rxn: carbox. Acid, ester, c=c

Question 11

NaBH4 rxn conditions

Answer 11

4:1 stoichiometry

polar protic solvent to protonate new OH

Racemic mixture (not aldehydes)

Question 12

Sterics in NaBH4

Answer 12

Ketone slower rxn, 2 R groups

Aldehyde faster rxn

Question 13

LiAlH4 reduces

Answer 13

Aldehyde –> 1°

Ketone –> 2°

Ester –> 1°

Carbox. Acid –> 1°

alkyl halide –> alkane

Question 14

LiAlH4 rxn conditions

Answer 14

4:1 stoichiometry

polar aprotic solvent to prevent H2 formation

racemic mixture (not aldehydes)

Question 15

LiAlH4 rxn with carbox. acid

Answer 15

need x2 excess of LiAlH4 because reacting with an acid