Reduction

Question 1

Reduction

Answer 1

Addition of H2, loss of O2, gain of electrons

Question 2

Catalytic hydrogenation

Answer 2

Alkenes to alkanes: H2 with Pd/C, syn addition onto less hindered face = concerted reaction, chemoselective with C=C only
Alkynes to alkenes: H2 with Lindsay catalyst, syn addition, poisoned stops at C=C

Question 3

Luche reduction

Answer 3

NaBH4 with CeCl3, CeCl3 = hard LA so activates C=O and C=C not reduced

Question 4

Protecting group for OH/NH

Answer 4

Benzyl group, added by Williamson ether synthesis

Question 5

Rosenmund reaction

Answer 5

Acid chloride to aldehyde, reagents = H2, Pd/BaSO4 and quinoline to poison catalyst
Very chemoselective for C-Cl

Question 6

Hydride reducing agents

Answer 6

NaBH4 and EtOH, LiAlH4 with THF

Question 7

What hydride reducing agent for what

Answer 7

NaBH4= aldehyde/ketone to alcohols
LiAlH4 = esters to alcohols,amides to amines, carboxylic acids to aldehydes then alcohols

Question 8

DIBAL

Answer 8

Di-isobutyl aluminium hydride, exists as a dimmer, becomes reducing agent only after forming a complex, reduces esters to aldehydes through tetrahedral intermediate

Question 9

NaCNBH3

Answer 9

Miler than NaBH4,useful for reductive animation of imines, can be done in one pot = chemoselective and doesn’t reduce C=O

Question 10

LiBH4

Answer 10

Reduces esters only

Question 11

Dissolving metal reductions

Answer 11

Na/Li in liquid ammonia that reduces any functional group with low energy π-orbital eg C=C, C=O and aromatic rings

Question 12

Birch reduction

Answer 12

Dissolving metal reduction, EWG = ipso/para = stabilisation of negative charge, EDG = ortho/meta = e- pair repulsion and reduction of alkynes gives trans alkenes