Chemical Reactions

Question 1

What type of reactions do aldehydes and ketones undergo

Answer 1

Nucleophilic addition reactions

Question 2

Mechanism of Nucleophilic addition reactions STEP 1

Answer 2

Nucleophile attacks the electrophilic carbon of the polar carbonyl group.(SLOW PROCESS)

Question 3

STEP 2 of mechanism

Answer 3

The hybridization changes from sp2 to sp3 and tetrahedral alkoxide intermediate is formed

Question 4

STEP 3 of mechanism

Answer 4

The intermediate captures a proton to give an electrically neutral product(FAST PROCESS)

Question 5

STEP 4 of mechanism

Answer 5

Addition of Nu- and H+ across the carbon oxygen double bond

Question 6

What happens when weak nucleophiles are used?

Answer 6

An acid catalyst must be used for the reaction to proceed

Question 7

Are aldehydes or Ketones more susceptible toward nucleophilic reactions

Answer 7

Aldehydes as
- sterically, the presence of 2 substituent groups hinders the approach of nucleophile in ketones whereas in aldehydes there is only 1 substituent group.
- electrically, 2 alkyl groups in ketones reduce its electrophilicity (lesser polarisation).

Question 8

What happens when the reaction is slow when aldehydes and ketones react with HCN

Answer 8

HCN is catalysed by a base and yields a cyanide ion which is a stronger nucleophile.

Question 9

Addition of HCN yields

Answer 9

Cyanohydrins.

Question 10

How can a hydrogen sulphite addition compound be converted back to the original carbonyl compound.

Answer 10

Treat it with dilute mineral acid or alkali.

Question 11

Addition of alcohol with aldehydes

Answer 11

Monohydric alcohol + Aldehydes–
->Hemiacetal + Alcohol —>Acetal

Question 12

Addition of which alcohol with ketone

Answer 12

Ethylene glycol

Question 13

Addition of ethylene glycol with ketone yields

Answer 13

Ethylene glycol ketals

Question 14

Reagent used to reduce aldehydes and ketones to alcohols

Answer 14

sodium borohydride(NaBH4) and litium aluminium hydrid(LiAlH4)

Question 15

Clemmensen Reduction

Answer 15

Carbonyl group + Zinc amalgam and HCl is reduced to CH2 group

Question 16

Wolff-Kishner Reduction

Answer 16

Carbonyl group + NH2NH2 to form hydrazone and heat with sodium/potassium hydroxide in ethylene glycol to reduce to CH2

Question 17

Oxidising agents

Answer 17

Nitric Acid, Potassium permanganate and potassium dichromate

Question 18

How is oxidation of Ketone different from that of aldehydes

Answer 18

Oxidation of Ketones involves carbon-carbon bond cleavage resulting in a mixture of carboxylic acids having lesser number of carbon atoms than the parent ketone.

Question 19

How to distinguish aldehydes from ketone

Answer 19

Tollens’ test and Fehling’s Test(for aldehydes) and Haloform(Ketones)

Question 20

Tollens’ reagent

Answer 20

Ammoniacal Silver nitrate solution

Question 21

Tollens’ Test

Answer 21

RCHO+2[AG(NH3)2] —>silver mirror and carboxylate anion

Question 22

Fehling’s solution A

Answer 22

aqueous copper sulphate solution

Question 23

Fehling’s solution B

Answer 23

Rochelle salt (Sodium potassium tartarate)

Question 24

Fehling’s Test

Answer 24

Aldehyde + Fehling’s reagent (A+B)—–
->reddish brown precipitate + carboxylate anion

Question 25

Which aldehyde does not respond to fehling's test

Answer 25

Aromatic aldehydes due to strong double bond character within benzene ring.

Question 26

Haloform reaction

Answer 26

Methyl ketone + sodium hypohalite ---- ->sodum salts of carboxylic acids and is converted to haloform.

Question 27

What is iodoform reaction used for

Answer 27

Iodoform + sodium hypoiodite is used for detection of CH3CO or CH3CH(OH) which produces CH3CO on oxidation.

Question 28

What is the reason behind the acidity of 𝛼-hydrogen atoms of carbonyl compounds?

Answer 28

Strong electron withdrawing effect and resonance stabilization of the conjugate base.

Question 29

Aldol reaction

Answer 29

One 𝛼-hydrogen undergo a reaction in the presence of dilute alkali to form aldol or ketol.

Question 30

Aldol condensation

Answer 30

The aldol and Ketol lose water to give 𝛼,β-unsaturated carbonyl compounds.

Question 31

Cross aldol condensation

Answer 31

carried out between two different aldehydes/ketones

Question 32

How many products are formed when both contains 𝛼-hydrogen atoms

Answer 32

4

Question 33

Cannizzaro Reaction

Answer 33

yields carboxylic acid and alcohol. for aldehydes with no 𝛼-hydrogen atom. undergoes self-oxidation and reducation on heating with KOH or NaOH.

Question 34

Electrophilic substitution reaction is observed in

Answer 34

Aromatic aldehydes and Ketones.(HNO3 AND H2SO4)

Question 35

Formalin

Answer 35

formaldehyde- to preserve biological specimens and to prepare bakelite

Question 36

Acetaldehyde

Answer 36

Manufacture of acetic acid, vinyl acetate, drugs and polymers.

Question 37

Benzaldehyde

Answer 37

in perfumery and dye industries

Question 38

Acetone and ethyl methyl ketone

Answer 38

industrial solvent

Question 39

Camphor, vanillin and acetophenone

Answer 39

known for their odours and flavors.