Carbonyl Compounds

Question 1

functional group

Answer 1

C=O

Question 2

2 homologusseriesofcarbonyl compounds

Answer 2

dehydes
ketones

Question 3

aldehydes general formula

Answer 3

Cn H2n+1 CHO

Question 4

how is an aldehyde formed

Answer 4

by dehydrating an alcohol

Question 5

general formula for ketones

Answer 5

Cn H2n+1 CO Cn H2n+1

R CO R’

Question 6

ending for ketones

Answer 6

…anone

Question 7

physical properties of ketones

Answer 7

simpler ketones have colourless liquids
simpler ketones dissolve in water due to hydrogen bonding

Question 8

how are ketones prepared

Answer 8

oxidation of secondary alcohols by warming with acidified potassium dichromate

Question 9

what types of reactions do ketones take part in

Answer 9

nucleophilic addition
condensation reactions

similar to aldehydes because of the carbonyl group in their structure

Question 10

reaction of ketones with Fehling’s and Tollen’s solutions

Answer 10

no reaction because ketones cannot be easily oxidized

hence, reactions with these reagents are used to distinguish between aldehydes and ketones

Question 11

compound name ending for aldehydes

Answer 11

…anal

Question 12

what happens in nucleophilic addition of aldehydes and ketones

Answer 12

1. the carbonyl C atom will be partially positive since it is bonded to the electronegative O atom
2. the negatively charged particles (nucleophiles) are attracted to the C atom
3. the nucleophile will add to the carbonyl C atom since this C atom is unsaturated

Question 13

in the mechanism of nucleophilic addition,what is the slow step

Answer 13

as the nucleophile approaches the carbonyl compound, the pi bond is broken so the nucleophile bonds to the C atom and a negatively charged intermediate is formed

Question 14

in the mechanism of nucleophilic addition, what is the fast step

Answer 14

the positively charged hydrogen bonds quickly to the negative O to complete the reaction

the reaction is done by adding a mixture of KCN and dilute acid to the aldehyde/ ketone, maintaining a temperature between 10-20 deg. C

Question 15

condensation reactions of aldehydes and ketones

Answer 15

carbonyl compounds react with the general formula H2X

during the reaction, the reagent loses H2 and the carbonyl compound loses O

water is eliminated

the carbonyl C atom then bonds to the X

*a double bond is not broken

Question 16

condensation reactions with 2,4-dinitrophenylhydrazine (2,4-dnp)

Answer 16

an orange or brown precipitate is formed
this is used to show the presence of a carbonyl group in the organic compound

Question 17

oxidation of aldehydes process

Answer 17

aldehydes are easily oxidized by gently warming with H2SO4 and K2Cr2O7 or H2SO4 and KMnO7

Question 18

what are aldehydes oxidized to

Answer 18

carboxylic acids

Question 19

how can you test for the CHO group in a compound

Answer 19

1. silver mirror test/ Tollen’s reagent
   test with Fehling’s solution

Question 20

test of aldehyde with fehling’s solution

Answer 20

forms a reddish brown precipitate

Question 21

test of aldehyde with fehling’s solution

Answer 21

forms a reddish brown precipitate

Question 22

silver mirror test with aldehydes

Answer 22

forms a silver precipitate

tollen’s reagent- AgNO3 + NH3

Question 23

reducing agents used in reduction of aldehydes

Answer 23

1. LiAlH4 (lithiumaluminiumhydride)
2. NaBH4 (sodiumborohydride)

Question 24

reduction of aldehydes

Answer 24

when an aldehyde is reacted with LiAlH4 in dry ether or NaBH4 in a mixture of H2O and CH3OH, the aldehyde is converted to a primary alcohol