aldehydes and ketones

Question 1

Aldehyde FG

Answer 1

CHO - think of ariella. C=O is on the end of the chain with an H attached

Question 2

Ketone FG

Answer 2

If the C=O is in the middle

Question 3

aldehydes and ketones are known as

Answer 3

carbonyls

Question 4

carbonyls and solubility

Answer 4

The smaller carbonyls are soluble in water because they can form hydrogen bonds with water. The longer the chain, the more insoluble

Question 5

intermolecular forces

Answer 5

pure carbonyls do not make Hydrogen bonds but permanent dipole forces

Question 6

what causes carbonyl reactions

Answer 6

the polar C=O bond, this bond is stronger than the alkene bond and is less prone to addition reactions

Question 7

three main reactions

Answer 7

addition, reduction, oxidation

Question 8

Oxidation reaction (primary)

Answer 8

primary alcohol–> aldehyde—> carboxylic acid

Question 9

Oxidation reaction (secondary)

Answer 9

secondary alcohol—> ketone

Question 10

Oxidation reaction (tertiary)

Answer 10

do not oxidise

Question 11

If you want to get a carboxylic acid from a primary alcohol

Answer 11

potassium dichromate (VI) solution and dilute sulphuric acid. Heat under reflux

Question 12

If you want to get an aldehyde from a primary alcohol

Answer 12

potassium dichromate (VI) solution and dilute sulphuric acid. distill

Question 13

observation in oxidation of propanal

Answer 13

the orange dichromate ion (Cr2O72-) reduces to the green Cr 3+ ion

Question 14

other ways of oxidising aldehydes

Answer 14

Tollen’s Reagent, Fehling’s solution

Question 15

how to make tollen’s

Answer 15

formed by mixing aqueous ammonia and silver nitrate. The active substance is the complex ion of [Ag(NH3)2]+ .

Question 16

Tollen’s Reagent (conditions)

Answer 16

heat gently

Question 17

Tollen’s Reagent (observation)

Answer 17

with aldehydes, a silver mirror forms coating the inside of the test tube. Ketones result in no change.

Question 18

Fehling’s solution (conditions)

Answer 18

heat gently

Question 19

Fehling’s solution (reaction)

Answer 19

aldehydes only are oxidised by Fehling’s Solution into a carboxylic acid and the copper ions are reduced to copper(I) oxide .

Question 20

Fehling’s solution (observation)

Answer 20

Aldehydes :Blue Cu 2+ ions in solution change to a red precipitate of Cu2O. Ketones do not react.

Question 21

what are aldehydes reduced to

Answer 21

primary alcohols

Question 22

what are ketones reduced to

Answer 22

secondary alcohols

Question 23

reagent and conditions for reducing aldehydes and ketones

Answer 23

NaBH4 or LiAlH4 at RTP

Question 24

what is the mechanism for reducing carbonyls

Answer 24

nucleophilic addition

Question 25

Propanal reduction equation

Answer 25

CH3CH2CHO + 2[H] = CH3CH2CH2OH

Question 26

propanone reduction equation

Answer 26

CH3COCH3 + 2[H] = CH3CHOHCH3

Question 27

how else can aldehydes and ketones be reduced

Answer 27

catalytic hydrogenation (H2 and Ni catalyst) high pressure

Question 28

how to make a hydroxynitrile from carbonyls

Answer 28

NaCN or HCN and dilute H2SO4
RTP
nucleophilic addition