Aldehydes, Ketones and Carboxylic Acids: Solution
Aldehydes, Ketones and Carboxylic Acids: Solution
Aldehydes, Ketones and Carboxylic Acids: Solution
(iv) 4-oxopentanal
(vi) 4-fluoroacetophenone
Solution.
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(i)
(ii)
(iii)
(iv)
Solution.
(i)
(ii)
(iii)
(iv)
Q.3 Arrange the following compounds in increasing order of their boiling points. CH 3CHO, CH3CH2OH,
CH3OCH3, CH3 CH2CH3
Hydrocarbons are non-polar having weakest attractive forces; Ethers are polar (dipolar forces); Aldehydes
have strong dipolar interactions; Alcohols have maximum inter molecular forces due to hydrogen
bonding.
Q.4 Arrange the following compounds in increasing order of their reactivity in nucleophilic addition
reactions.
(i) Butanone (C2H5COCH3) < propanone (CH3COCH3) < propanal (C2H5CHO) < ethanol (CH3COCH3)
(i) PhCH2CH2COOH
(ii) (CH3)2C=CHCOOH
(iii)
(iv)
Q.7 Show how each of the following compounds can be converted to benzoic acid?
(ii) Acetophenone
(iii) Bromobenzene
Q.8 What is meant by the following terms? Give an example of the reaction in each case.
Solution. (i) Cyanohydrin Addition products formed by the reaction of aldehydes and ketones with
hyfrogen cyanide (HCN) are known as cyanohydrins.
(i) CH3CH(CH3)CH2CH2CHO
(ii) CH3CH2COCH(C2H5)CH2CH2Cl
(iv) CH3COCH2COCH3
(v) CH3CH(CH3)CH2C(CH3)COCH3
(vi) (CH3)3CCH2COOH
(vii) OHCC6G4CHO-þ
(i) The 2,4-dinitro phenyl hydrazone of benzaldehyde (iv) The semicarbazoneof cyclobutanone
Q.12 Predict the products formed when cyclohexane carbaldehyde reacts with following reagents.
Q.13 How will you convert ethanol. In each case, indicate which aldehyde acts as nucleophile and which as
electrophile?
Q.14 Write structural formulas and names of four possible aldol condensation products from propanal and
butanal. In each case, indicate which aldehyde acts as nucleophile and which as electrophile?
Q.15 An organic compound with (A) (molecular formula (C8H16O2) was hydrolysed with dilute sulphuric acid
to give a carboxylic acid (B) and alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on
dehydration gives but-1-ene. Write equations for the reactions involved.
Solution.(i) The compound with molecular formula C9H10O from a 2,4-DNP derivative and reduces Tollen’s
reagent, so it is an aldehyde.
(ii) It undergoes Cannizzaro reaction, so the aldehyde group should be directly attached to the benzene ring.
(iii) On vigorous oxidation, it gives 1,2- benzene dicarboxylic acid, so it should be an ortho substituted
benzaldehyde. For molecular formula C9H10O, the possibility is only o-ethyl benzaldehyde.
(iv) The equations for all the reactions are given below:
Q.16 Arrange the following compounds in increasing order of their property as indicated:
(i) Acetakdehyde, acetone, di-tert-butyl ketone, methyl tert-butyl ketone (reactivity towards HCN).
(iii)Benzoic acid, 4-nitrobenzoic acid, 3,4-dinitro benzoic acid, 4-methoxy benzoic acid (acid strength).
Solution.
Q.17 Give simple chemical tests to distinguish between the following pairs of compoundsn.
Q.18 How will you prepare the following compounds from benzene? You may use any inorganic regent and
any organic reagent having not more than one carbon atom.
(iv) P-nitrobenzaldehyde.
Q.19 How will you bring about the following conversion in not more than two steps?
(v)Benzaldehyde to benzophenone
(i) Acetylation
(iv) Decarboxylation
(i) Cyclohexanone forms cyanohydrins in good yield bur 2,2,6-trimethyl cyclohexanone does not.
(ii) These are two _NH2 groups in semicarbazide. However, only one is involved in the formation of
bsemicarvazones.
(ii) During the preparation of esters from a carboxylic acid and an alcohol in the presence of an acid
catalyst, th water or the ester should be removed as soon as it is formed.
Q.19 An organic compound contains 69.77 % carbon, 11.63% hydrogen and rest oxygen. The molecular
mass of the compound is 86. It does not reduce Tollen’s reagent but forms an addition compound with
sodium hydrogen sulphite and give positive iodoform test. On vigorous oxidation it gives ethanoic and
propanoic acid. Write the possible structure of the compound.
Q. 20 Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylic acid
is a stronger acid than phenol. Why?
Q. 21 Why is there a large difference in the boiling points of butanal and butan-1lol?
Q.23 Benzaldehyde can be obtained from benzal chloride. Write reactions for obtaining benzal chloride and
then bezaldehyde from it.
Q.24 Arrange the following in decreasing order of their acidic strength and give reason for your answer.
CH3CH2OH; CH3COOH; CICH2COOH; FCH2COOH; C6H5CH2COOH
Q.25 Compound ‘A’ was prepared by oxidation of compound ‘B’ with alkaline KMnO4. Compound ‘A’ on
reduction with lithium aluminium hydride gets converted back to compound ‘B’. When compound ‘A’ is
heated with compound B in the presence of H2SO4, it produces fruity smell of compound C to which family
the compounds ‘A’, ‘B’ and ‘C’ belong to?
Q. 27 Why are carboxylic acids more acidic than alcohols or phenols athough all of them have hydrogen atom
attached to a oxygen atom (—O—H)?
Q.29 An aromatic compound ‘A’ (molecular formula C8H8O) gives positive 2,4-DNP test. It gives a yellow
precipitate of compound ‘B’ on treatment with iodine and sodium hydroxide solution. Compound ‘A’
does not give Tollen’s or Fehling’s test. On drastic oxidation with potassium permanganate is forms a
carboxylic acid ‘C’ (molecular formula C7H6O2), which is also formed along with the yellow compound in
the above reaction. Identify A, B and C and write all the reactions involved
Q. 30 Write down functional isomers of a earbonyl compound with molecular formula C 3H6O. Which isomer
will react faster with HCN and why? Explain the mechanism of the reaction also, Will the reaction lead to
the completion with the conversion of whole reactant into product at reaction conditions? If a strong
acid is added to the reaction mixture what will be the effect on concentration of the product and why?