Aldehydes And Ketones

Question 1

Primary alcohol to aldehyde conditions and reagent

Answer 1

Oxidation
K2Cr2O7 +H2SO4
Heat and distil off product

Question 2

Aldehyde to primary alcohol conditions

Answer 2

Aqueous NaBH4
Reduction

Question 3

Aldehyde to carboxylic acid conditions

Answer 3

Tollens or fehlings or
K2Cr2O7+H2SO4
Heat or reflux
Oxidation

Question 4

Secondary alcohol to ketone

Answer 4

Oxidation
K2Cr2O7 +H2SO4
Heat or reflux

Question 5

Ketone to secondary alcohol

Answer 5

Aqueous NaBH4
Reduction

Question 6

Ketone to carboxylic acid

Answer 6

DOESNT REACT

Question 7

K2Cr2O7 +H2SO4

Answer 7

Orange Cr2O72- ions are reduced to green Cr3+ ions as they oxidise the alcohol/aldehyde

Question 8

Tollens reagent

Answer 8

Contains [Ag(NH3)2]+ ions that are reduced to a silver mirror as it oxidised the aldehyde to a carboxylic acid

Question 9

Fehlings reagent

Answer 9

Blue solution contains Cu2+ ions which are reduced to a brick red ppt of Cu2O as it oxidised the aldehyde to a carboxylic acid

Question 10

Reaction of aldehydes and ketones to form alcohols

Answer 10

NaBH4 aqueous
Primary alcohol formed from aldehyde and secondary from ketone

Question 11

Reaction of aldehydes and ketones to form hydroxynitriles (racemates)

Answer 11

Aqueous KCN followed by dilute acid

Question 12

Why does the addition of KCN normally form a racemic mixture

Answer 12

Due to the planar nature of the C=O group, the CN- ion has an equal chance of attaching the delta positive from above or below

Question 13

Why isn’t HCN used instead of KCN?

Answer 13

toxic and weakly acidic do don’t get many H+‘a and CN-‘s