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Aldehydes and Ketones > Chemical Reactions > Flashcards

Chemical Reactions Flashcards

1
Q

What type of reactions do aldehydes and ketones undergo

A

Nucleophilic addition reactions

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2
Q

Mechanism of Nucleophilic addition reactions STEP 1

A

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

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3
Q

STEP 2 of mechanism

A

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

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4
Q

STEP 3 of mechanism

A

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

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5
Q

STEP 4 of mechanism

A

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

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6
Q

What happens when weak nucleophiles are used?

A

An acid catalyst must be used for the reaction to proceed

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7
Q

Are aldehydes or Ketones more susceptible toward nucleophilic reactions

A

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).

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8
Q

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

A

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

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9
Q

Addition of HCN yields

A

Cyanohydrins.

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10
Q

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

A

Treat it with dilute mineral acid or alkali.

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11
Q

Addition of alcohol with aldehydes

A

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

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12
Q

Addition of which alcohol with ketone

A

Ethylene glycol

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13
Q

Addition of ethylene glycol with ketone yields

A

Ethylene glycol ketals

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14
Q

Reagent used to reduce aldehydes and ketones to alcohols

A

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

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15
Q

Clemmensen Reduction

A

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

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16
Q

Wolff-Kishner Reduction

A

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

17
Q

Oxidising agents

A

Nitric Acid, Potassium permanganate and potassium dichromate

18
Q

How is oxidation of Ketone different from that of aldehydes

A

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.

19
Q

How to distinguish aldehydes from ketone

A

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

20
Q

Tollens’ reagent

A

Ammoniacal Silver nitrate solution

21
Q

Tollens’ Test

A

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

22
Q

Fehling’s solution A

A

aqueous copper sulphate solution

23
Q

Fehling’s solution B

A

Rochelle salt (Sodium potassium tartarate)

24
Q

Fehling’s Test

A

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

25
Q

Which aldehyde does not respond to fehling’s test

A

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

26
Q

Haloform reaction

A

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

27
Q

What is iodoform reaction used for

A

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

28
Q

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

A

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

29
Q

Aldol reaction

A

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

30
Q

Aldol condensation

A

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

31
Q

Cross aldol condensation

A

carried out between two different aldehydes/ketones

32
Q

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

A

4

33
Q

Cannizzaro Reaction

A

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

34
Q

Electrophilic substitution reaction is observed in

A

Aromatic aldehydes and Ketones.(HNO3 AND H2SO4)

35
Q

Formalin

A

formaldehyde- to preserve biological specimens and to prepare bakelite

36
Q

Acetaldehyde

A

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

37
Q

Benzaldehyde

A

in perfumery and dye industries

38
Q

Acetone and ethyl methyl ketone

A

industrial solvent

39
Q

Camphor, vanillin and acetophenone

A

known for their odours and flavors.

Aldehydes and Ketones (4 decks)

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