Question 1

Reaction between benzaldehyde and acetophenone in presence of dilute NaOH is known as:

Accepted Answer

In the presence of dil. OH(−), benzaldehyde and acetophenone will react to undergo cross-aldol condensation.

Question 2

Which of the following alkane cannot be made in good yield by Wurtz reaction?

Accepted Answer

Wurtz reaction is used to prepare symmetrical alkanes like R1​−R1​, asR1​−X+2Na+X−R1​Dryether​R1​−R1​+2NaX  If R1​ and R2​ are different, then mixture of alkanes may be obtained asR1​−X+2Na+R2​−XDryether​ R1​−R1​+R1​−R2​+R2​−R2​+2NaX

Question 3

Carboxylic acids have higher boiling points than aldehydes, ketones and even alcohols of comparable molecular mass. It is due to their :

Accepted Answer

Due to formation of intermolecular H -bonding in carboxylic acid, association occurs. Hence boiling point increases and become more than the boiling point of aldehydes, ketones and alcohols of comparable molecular masses.

Question 4

Compound A, C8​H10​O, is found to react with NaOI (produced by reacting Y with NaOH) and yields a yellow precipitate with characteristic smell.A and Y are respectively :

Accepted Answer

Option (1) is secondary alcohol which on oxidation gives phenylmethyl ketone (Acetophenone). This on reaction with I2​  and NaOH  form iodoform and sodium benzoate.

Question 5

The IUPAC name of the compound

Accepted Answer

Aldehydes get higher priority over ketone and alkene in numbering of principal C-chain.
∴ 3-keto-2-methylhex-4-enal

Question 6

Reaction of a carbonyl compound with one of the following reagents involves nucleophilic addition followed by elimination of water. The reagent is:

Accepted Answer

With Ammonia derivation carbonyl compounds give addition followed by elimination reaction. Slightly acidic medium will generate a nucleophilic centre for weak base like ammonia derivatives.

Question 7

Which one of the following esters gets hydrolyzed most easily under alkaline conditions?

Accepted Answer

EWG (Electron withdrawing group) increases reactivity towards nucleophilic substitution reaction. −NO2​ is strong electron withdrawing group.

Question 8

What is meant by the following terms ? Give an example of the reaction in each case.(i) Cyanohydrin            (ii) Acetal            (iii) Semicarbazone(iv) Aldol                 (v) Hemiacetal         (vi) Oxime(vii) Ketal                (vii) Imine            (ix) 2,4-DNP-derivative(x) Schiffs base

Accepted Answer

(i) Cyanohydrin :−OH group and cyano group are present on same carbon atom. Addition of HCN to carbonyl group in weakly acidic medium forms cyanohydrin.CH3​CHO+HCNpH9−10​CH3​CH(OH)CN(ii) Acetal :TerminalC atom has two alkoxy groups. Two equivalents of monohydric alcohol add to 1 equivalent of aldehyde in presence of dry HCl gas. CH3​CHO+2CH3​OHDryHCl​CH3​CH(OCH3​)2​+H2​O(iii) Semicarbazone :Derivative of aldehyde or ketone obtained on treatment with semicarbazide in weakly acidic medium.H3​CCHO+H2​NNHCONH2​pH3.5−H2​O​CH3​CH=NNHCONH2​(iv) Aldol   :                          Beta hydroxy aldehyde or ketone obtained by condensation of 2 molecules of aldehydes or ketones containing alpha hydrogen atoms in presence of dilute aqueous base.2CH3​CHOOH−​CH3​CHOHCH2​CHO(v) Hemiacetal  :           Gem alkoxy alcohols obtained by addition of one molecule of monohydric alcohol to aldehyde in presence of dry HCl gas.CH3​CHO+CH3​OH⇌CH3​CH(OH)OCH3​(vi) Oxime :Aldehydes or ketones react with hydroxyl amine in weakly acidic mediumCH3​CHO+H2​NOH→CH3​CH+NOH(vii) Ketal :                           Gem dilkoxy alkanes obtained by the reaction of ketone with ethylene glycol in presence of dry HCl. Two alkoxy groups are present on same C atom.CH3​COCH3​+HOCH2​CH2​OH​(CH3​)2​C(OC​H2​−)2​(vii) Imine :                    They contain−CH=N− group obtained by the reaction between aldehydes and ketones with ammonia derivatives such as hydrazine, hydroxylamine, phenyl hydrazine, semicarbazide etc. CH3​COCH3​+PhNH−NH2​→(CH3​)2​C=NNHPh(ix) 2,4-DNP-derivative :Derivatives obtained by the reaction of aldehydes and ketones with 2,4-DNP (2,4-dinitrophenylhydrazone) in weakly acidic medium.CH3​COCH3​+H2​NNH−C6​H4​(NO2​)2​pH=3.5−H2​O​(CH3​)2​C+NNH−C6​H4​(NO2​)2​(x) Schiffs base :Azomethines obtained by the reaction of aldehydes and ketones with primary amines (aliphatic or aromatic).PhCHO+PHNH2​H+Δ​PhCH=NHPh+H2​O

Question 9

Name the following compounds according to IUPAC system of nomenclature:(i) CH3​CH(CH3​)CH2​CH2​CHO (ii) CH3​CH2​COCH(C2​H5​)CH2​CH2​Cl(iii) CH3​CH=CHCHO(iv) CH3​COCH2​COCH3​(v) CH3​CH(CH3​)CH2​C(CH3​)2​COCH3​(vi) (CH3​)3​CCH2​COOH(vii) OHCC6​H4​CHO−p

Accepted Answer

(i) 4-Methylpentanal(ii) 6-chloro-4-ethylhexan-3-one(iii) but-2-enal(iv) pentane-2,4-dione(v) 3,35-trimethylhexan-2-one(vi) 3,3-dimethylbutanoic acid(vii) Benzene-1,4-dicarbaldehyde

Question 10

Write the IUPAC names of the following ketones and aldehydes. Wherever possible, give also common names.(i) CH3​CO(CH2​)4​CH3​ (ii) CH3​CH2​CHBrCH2​CH(CH3​)CHO (iii) CH3​(CH2​)5​CHO (iv) Ph−CH=CH−CHO (v) (vi) PhCOPh

Accepted Answer

(i) IUPAC Name: Heptan-2-oneCommon Name:Methyl n-pentyl ketone (ii)  IUPAC Name:4-Bromo-2-methylhexanalCommon Name:γ -bromo-α methylhexanal(iii) IUPAC Name: Heptanal(iv)  IUPAC Name: 3-Phenylprop-2-enal(v) IUPAC Name: Cyclopentacarbaldehyde(vi)IUPAC Name: Diphenyl methanone    Common Name: Benzophenone

Question 11

Draw structures of the following derivatives.(i) The 2,4-dinitrophenylhydrazone of benzaldehyde(ii) Cyclopropanone oxime(iii) Acetaldehydedimethylacetal(iv) The semicarbazone of cyclobutanone(v) The ethylene ketal of hexan-3-one(vi) The methyl hemiacetal of formaldehyde

Accepted Answer

The required structures are as shown.

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Solution for Class 12, Chemistry, Aldehydes, Ketones and Carboxylic Acids

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