Aldehydes And Ketones MCQs with Answers
Which of the following functional groups is characteristic of both aldehydes and ketones?
Hydroxyl group
Carboxyl group
Carbonyl group
Ether group
In an aldehyde, the carbonyl group is bonded to at least one:
Alkyl group
Oxygen atom
Carbon atom
Hydrogen atom
What is the general formula for a ketone?
R-CHO
R-COOH
R-C(=O)-R'
R-O-R'
The common name for H-C(=O)-H is:
Acetaldehyde
Formaldehyde
Propanal
Butyraldehyde
What is the IUPAC name for CH₃-C(=O)-H?
Methanal
Propanal
Ethanal
Butanone
Which of the following aldehydes would have "Propionaldehyde" as its common name?
H-C(=O)-H
CH₃-C(=O)-H
CH₃-CH₂-C(=O)-H
CH₃-CH₂-CH₂-C(=O)-H
In the common naming of aldehydes, Greek letters are used to indicate the positions of other groups. Which letter indicates the carbon atom adjacent to the carbonyl group?
What is the common name for CH₃-C(=O)-CH₃?
Ethyl methyl ketone
Acetone
Diethyl ketone
Propanone
When naming ketones using common names, how are the alkyl groups listed?
By size (smallest to largest)
By size (largest to smallest)
Alphabetically
In order of their attachment to the carbonyl carbon
What is the IUPAC name for CH₃-CH₂-C(=O)-CH₃?
2-Propanone
Butanone
Acetone
Ethyl methyl ketone
Aldehydes are generally obtained by the oxidation of which type of alcohols?
Tertiary alcohols
Secondary alcohols
Primary alcohols
Phenols
Ketones are generally prepared by the oxidation of which type of alcohols?
Primary alcohols
Secondary alcohols
Tertiary alcohols
Enols
Besides the oxidation of secondary alcohols, ketones can also be prepared by the:
Hydration of alkanes
Hydration of alkynes
Dehydration of primary alcohols
Reduction of carboxylic acids
In the laboratory preparation of formaldehyde, methyl alcohol vapours and air are passed over which catalyst at 300 °C?
Nickel catalyst
Platinised asbestos
Zinc oxide
Palladium chloride
Formalin is a mixture containing 40% formaldehyde, 8% methyl alcohol, and what percentage of water?
For the industrial preparation of formaldehyde, methanol vapours and air are passed over which catalyst at 500 °C?
Platinum
Copper
Iron oxide-molybdenum oxide
Zinc amalgam
In the laboratory preparation of acetaldehyde, ethyl alcohol is oxidized using:
Neutral KMnO₄ solution
Acidified sodium dichromate solution
Basic K₂Cr₂O₇ solution
Hydrogen peroxide
Why is acetaldehyde distilled off immediately during its laboratory preparation from ethyl alcohol oxidation?
To increase the yield
To prevent its polymerization
To prevent its further oxidation to acetic acid
To separate it from unreacted ethyl alcohol
Acetaldehyde can also be prepared by the dry distillation of a mixture of calcium salts of which two acids?
Acetic acid and propanoic acid
Formic acid and acetic acid
Butyric acid and formic acid
Oxalic acid and malonic acid
Industrially, acetaldehyde is prepared by the air oxidation of ethylene using which catalyst system?
Ni/Al₂O₃
FeO₃/Mo₂O₃
Palladium chloride catalyst
Raney Nickel
Acetone is prepared by the dry distillation of:
Calcium formate
Calcium propanoate
Calcium acetate
Calcium oxalate
The industrial method for formaldehyde production uses a temperature of 500 °C, while the laboratory method uses:
In the preparation of formaldehyde in the laboratory, what is used to draw air through methyl alcohol?
A condenser
A suction pump
A heating mantle
A dropping funnel
The reaction: 2CH₃OH + O₂ —Pt-asbestos, 300°C→ 2H−C=O + 2H₂O represents the laboratory preparation of:
Acetaldehyde
Acetone
Formaldehyde
Ethanol
The carbonyl group possesses a σ-bond and a π-bond, allowing it to primarily undergo which type of reactions?
Elimination reactions
Substitution reactions
Addition reactions
Rearrangement reactions
Why is the carbonyl group considered a polar group?
Carbon is more electronegative than oxygen.
Oxygen tends to attract electrons to itself, creating partial charges.
The double bond restricts electron movement.
It has a linear geometry.
In the carbonyl group (C=O), which atom has a partial positive charge and is electrophilic?
Oxygen atom
Carbon atom
Both carbon and oxygen atoms
Neither carbon nor oxygen atom
The characteristic reactions of carbonyl compounds are primarily:
Electrophilic substitution reactions
Free radical addition reactions
Nucleophilic addition reactions
Acid-base reactions
In nucleophilic addition reactions of aldehydes and ketones, which part of the reagent typically combines with the electrophilic carbon of the carbonyl group?
The positive part
The negative part
The neutral part
Both positive and negative parts simultaneously
How does a base catalyst affect nucleophilic addition reactions of carbonyl compounds?
It decreases the electrophilic character of the carbonyl carbon.
It increases the positive character of the carbonyl carbon.
It increases the nucleophilic character of the reagent.
It facilitates the removal of the positive part of the reagent.
How does an acid catalyst promote nucleophilic attack in carbonyl compounds?
By generating a strong nucleophile
By decreasing the electrophilic character of the carbonyl carbon
By increasing the electrophilic character of the carbonyl carbon atom.
By stabilizing the negative charge on oxygen.
In nucleophilic addition reactions of aldehydes and ketones, the positive part of the reagent, which is usually hydrogen, goes to which atom?
The carbon atom of the carbonyl group
The oxygen atom of the carbonyl group
An adjacent alkyl group
The solvent
Which statement accurately compares the adduct formed in base-catalysed versus acid-catalysed nucleophilic addition reactions?
The adduct is different for each catalyst.
The adduct is the same for both catalysts.
Base-catalysed reactions form a more stable adduct.
Acid-catalysed reactions form a more stable adduct.
The first step in a base-catalysed nucleophilic addition reaction involves:
Protonation of the carbonyl oxygen.
Attack of an electrophile on the carbonyl carbon.
The base reacting with the reagent to generate the nucleophile.
Formation of a carbocation.
What is the general characteristic reaction of carbonyl compounds like aldehydes and ketones?
Electrophilic substitution
Free radical addition
Nucleophilic addition
Elimination
In nucleophilic addition reactions, which atom of the carbonyl group is attacked by the nucleophile?
Oxygen atom
Carbon atom
Both carbon and oxygen atoms simultaneously
Hydrogen atom (if present)
Which of the following describes the role of a base catalyst in nucleophilic addition reactions?
It protonates the carbonyl oxygen.
It increases the electrophilic character of the carbonyl carbon.
It increases the nucleophilic character of the reagent.
It removes water from the reaction.
How does an acid catalyst facilitate nucleophilic addition reactions?
By decreasing the electrophilic character of the carbonyl carbon.
By generating a stronger nucleophile.
By increasing the positive character of the carbonyl carbon atom.
By stabilizing the negative charge on the attacking nucleophile.
The addition of hydrogen cyanide (HCN) to aldehydes and ketones results in the formation of:
Alkenes
Cyanohydrins
Carboxylic acids
Amines
In the addition of HCN to a carbonyl compound, the reaction is usually catalysed by:
Strong acid
Strong base
Lewis acid
Neutral salt
Which of the following is a key step in the base-catalysed addition of HCN?
Protonation of the carbonyl oxygen.
Reaction of the base with HCN to generate CN⁻.
Attack by H⁺ on the carbonyl carbon.
Elimination of water.
What type of compounds are formed when Grignard reagents react with aldehydes and ketones, followed by hydrolysis?
Carboxylic acids
Alkanes
Alcohols
Ethers
Reaction of formaldehyde with a Grignard reagent, followed by hydrolysis, gives a:
Secondary alcohol
Tertiary alcohol
Primary alcohol
Ether
Reaction of any aldehyde (other than formaldehyde) with a Grignard reagent, followed by hydrolysis, gives a:
Primary alcohol
Secondary alcohol
Tertiary alcohol
Alkene
Reaction of a ketone with a Grignard reagent, followed by hydrolysis, gives a:
Primary alcohol
Secondary alcohol
Tertiary alcohol
Aldehyde
What is the product formed when sodium bisulphite adds to an aldehyde or ketone?
An insoluble solid
A bisulphite addition product
An alkene
A carboxylic acid
The bisulphite addition product is generally crystalline and water-soluble. How can the original aldehyde or ketone be regenerated from it?
By oxidation
By heating with acid or alkali
By reduction
By reaction with HCN
The addition of sodium bisulphite is reversible. For which type of carbonyl compounds is this addition particularly useful for purification?
Only large ketones
Only aromatic aldehydes
Low molecular weight aldehydes and ketones
High molecular weight aldehydes only
What type of reaction involves the joining of two molecules with the elimination of a small molecule like water?
Substitution reaction
Addition reaction
Condensation reaction
Rearrangement reaction
What kind of compounds are formed when aldehydes and ketones react with ammonia derivatives?
Ethers
Alcohols
Compounds containing the C=N-G group and water
Carboxylic acids
The reaction of aldehydes and ketones with ammonia derivatives is considered a condensation reaction because:
It requires high pressure.
Water is lost after addition occurs.
It forms a larger molecule.
It is reversible.
The reaction of aldehydes and ketones with ammonia derivatives is typically catalysed by:
Why are aldehydes generally more reactive than ketones towards nucleophilic addition reactions?
Aldehydes are more sterically hindered.
The carbonyl carbon in aldehydes is less electrophilic.
Ketones have two bulky alkyl groups increasing steric hindrance and decreasing electrophilicity.
Aldehydes have stronger C=O bonds.
Which of the following compounds would be most reactive towards nucleophilic addition?
Acetone
Acetaldehyde
Formaldehyde
Diethyl ketone
Aldehydes can be reduced to which type of alcohol?
Tertiary alcohol
Secondary alcohol
Primary alcohol
Dihydric alcohol
Ketones can be reduced to which type of alcohol?
Primary alcohol
Secondary alcohol
Tertiary alcohol
Trihydric alcohol
Which of the following is a common reducing agent used for the reduction of aldehydes and ketones to alcohols?
KMnO₄
K₂Cr₂O₇
NaBH₄
Tollens' reagent
The reduction of aldehydes and ketones using hydrogen in the presence of a catalyst like nickel or platinum is known as:
Oxidation
Hydrogenation
Hydration
Dehydration
What type of reaction is the reduction of a carbonyl group to a hydroxyl group?
Oxidation
Addition reaction
Substitution reaction
Elimination reaction
Which of the following reducing agents is generally more powerful and used for a wider range of reductions, including carboxylic acids?
NaBH₄
LiAlH₄
Zn-Hg/HCl
Na/C₂H₅OH
When 2-propanone (acetone) is reduced, what is the product formed?
1-propanol
2-propanol
Propanal
Propane
The reduction of ethanal will yield:
Methane
Ethanol
Ethanoic acid
Ethane
The general equation for the reduction of an aldehyde to a primary alcohol can be represented as:
R-CHO + [O] → R-COOH
R-CHO + 2[H] → R-CH₂OH
R-C(=O)-R' + 2[H] → R-CH(OH)-R'
R-CH₂OH → R-CHO + H₂
Which reduction method for aldehydes and ketones involves the use of sodium and ethanol?
Catalytic hydrogenation
Clemmensen reduction
Wolff-Kishner reduction
Bouveault-Blanc reduction
Aldehydes are generally oxidized to which class of compounds?
Alcohols
Alkenes
Carboxylic acids
Esters
Why are aldehydes more easily oxidized than ketones?
Because of the presence of a hydrogen atom directly attached to the carbonyl carbon.
Because of the presence of an alkyl group.
Because of steric hindrance.
Because ketones have stronger C=O bonds.
Which of the following is a strong oxidizing agent used to oxidize aldehydes to carboxylic acids?
NaBH₄
LiAlH₄
Acidified potassium dichromate
Sodium bisulphite
Which reagent is commonly used to distinguish between aldehydes and ketones due to its ability to oxidize aldehydes but not most ketones?
Grignard reagent
Sodium borohydride
Tollens' reagent
Hydrogen cyanide
What is the characteristic visible change observed when an aldehyde reacts with Tollens' reagent?
Formation of a yellow precipitate.
Evolution of a gas.
Formation of a silver mirror or black precipitate.
Disappearance of purple color.
Tollens' reagent is an ammoniacal solution of:
Cupric oxide
Silver nitrate
Ferric chloride
Lead acetate
When an aldehyde is oxidized by Fehling's solution, what characteristic change is observed?
Formation of a silver mirror.
Disappearance of blue color and formation of a red precipitate.
Evolution of carbon dioxide.
Formation of a yellow solution.
Fehling's solution consists of two solutions, Fehling's solution A and Fehling's solution B. What is Fehling's solution B?
Aqueous copper sulfate
Alkaline solution of sodium potassium tartrate
Ammoniacal silver nitrate
Dilute nitric acid
Ketones can be oxidized under vigorous conditions (strong oxidizing agents and high temperature) resulting in the cleavage of C-C bonds adjacent to the carbonyl group. What is the usual outcome regarding the number of carbon atoms in the products?
Products with more carbon atoms than the original ketone.
Products with the same number of carbon atoms as the original ketone.
A mixture of carboxylic acids with fewer carbon atoms than the original ketone.
Alkenes with fewer carbon atoms.
The Haloform reaction is a specific oxidation reaction that detects the presence of:
All aldehydes
All ketones
secondary alcohols
Carboxylic acids
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