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Questions:

Case Study Questions

5 x 4 = 20

Read the passage given below and answer the following questions:
Aldehydes and ketones having acetyl group are oxidised by sodium hypohalate (NaOX) or halogen and alkali (X₂ + OH^-) to corresponding sodium salt having one carbon atoms less than the carbonyl compound and give a haloform.

Sodium hypoiodite (NaOI) when treated with compounds containing CH₃CO - group gives yellow precipitate of iodoform. Haloform reaction does not affect a carbon-carbon double bond present in the compound.
The following questions are multiple choice questions. Choose the most appropriate answer:

(a) Isopropyl alcohol	(b) Propionaldehyde
(c) Ethylphenyl ketone	(d) Benzyl alcohol

(ii) Which of the following compounds is not formed in iodoform reaction of acetone?

(a) CH₃COCH₂I	(b) ICH₂COCH₂I
(c) CH₃COCHI₂	(d) CH₃COCI₃

(iii) For the given set of reactions

starting compound A corresponds to

(iv) An organic compound 'A' has the molecular formula C₃H₆O. It undergoes iodoform test. When saturated with HCI it gives 'B' of molecular formula C₉H₁₄O. 'A' and 'B' respectively are

(a) propanal and mesityl oxide	(b) propanone and mesityl oxide
(c) propanone and 2,6-dimethyl-2,5-hepta-dien-4-one	(d) propanone and propionaldehyde

Read the passage given below and answer the following questions :
Carboxylic acids dissociate in water to give carboxylate ion and hydronium ion.
RCOOH + H₂O \(\longrightarrow\) RCOO^- + H3O⁺
The acidity of carboxyl group is due to the presence of positive charge on oxygen which liberates proton. The carboxylate ion formed is resonance stabilised.

Carboxylic acids are stronger acids than phenols. Electron withdrawing groups (EWG) increase the acidity of carboxylic acids by stabilising the conjugate base through delocalisation of negative charge by inductive and/ or resonance effects. Electron donating group (EDG) decrease the acidity by destabilising the conjugate base.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Which of the following reactions is showing the acidic property of carboxylic acid?

(ii) Which one of the following is the correct order of acidic strength?

(a) CF₃COOH > CHCl₂COOH > HCOOH > C₆H₅CH₂COOH > CH₃COOH

(b) CH₃COOH > HCOOH > CF₃COOH > CHCl₂COOH > C₆H₅CH₂COOH

(c) HCOOH > C₆H₅CH₂COOH > CF₃COOH > CHCl₂COOH > CH₃COOH

(d) CF₃COOH > CH₃COOH > HCOOH > CHCl₂COOH > C₆H₅CH₂COOH

(iii) Which of the following acids has the smallest dissociation constant?

(a) CH₃CHFCOOH	(b) FCH₂CH₂COOH
(c) BrCH₂CH₂COOH	(d) CH₃CHBrCOOH

(iv) The correct order of acidity for the following compounds is

(a) I > II > III > IV	(b) III > I > II > IV
(c) III> IV > II> I	(d) I > III > IV > II

Read the passage given below and answer the following questions
A tertiary alcohol H upon acid catalysed dehydration gives a product I. Ozonolysis of I leads to compounds J and K. Compound J upon reaction with KOH gives benzyl alcohol and a compound L, whereas K on reaction with KOH gives only M.

The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Compound H is formed by the reaction of

(ii) The structures of compound J, Kand L, respectively, are

(a) PhCOCH₃ , PhCH₂COCH₃ and PhCH₂COO^-K⁺	(b) PhCHO, PhCH₂CHO and PhCOO^-K⁺
(c) PhCOCH₃, PhCH₂CHO and CH3 COO^-K⁺	(d) PhCHO, PhCOCH₃ and PhCOO^-K⁺

(iii) When (J) is treated with acetic anhydride, in the presence of corresponding salt of an acid, the product obtained is

(a) cinnamic acid

(b) crotonic acid

(c) maleic acid

(d) benzylic acida

(iv) Which of the following statements is correct for compound (K)?

(a) It reacts with alkaline KMnO₄ followed by acidic hydrolysis and forms benzoic acid.

(b) It reacts with iodine and NaOH to form triiodomethane.

(c) It is prepared by the reaction of benzene with benzoyl chloride in presence of anhydrous aluminium chloride

(d) It reacts with freshly prepared ammoniacal silver nitrate solution

Read the passage given below and answer the following questions :
When an aldehyde with no a-hydrogen reacts with concentrated aqueous NaOH, half the aldehyde is converted to carboxylic acid salt and other half is converted to an alcohol. In other words, half of the reactant is oxidized
and other half is reduced. This reaction is known as Cannizzaro reaction

The following questions are multiple choice questions. Choose the most appropriate answer :
(i) A mixture of benzaldehyde and formaldehyde on heating with aqueous NaOH solution gives

(a) benzyl alcohol and sodium formate	(b) sodium benzoate and methyl alcohol
(c) sodium benzoate and sodium formate	(d) benzyl alcohol and methyl alcohol.

(ii) Which of the following compounds will undergo Cannizzaro reaction?

(a) CH₃CHO	(b) CH₃COCH₃
(c) C₆H₅CHO	(d) C₆H₅CH₂CHO

(iii) Trichloroacetaldehyde is subjected to Cannizzaro's reaction by using NaOH. The mixture of the products contains sodium trichloroacetate ion and another compound. The other compounds is

(a) 2, 2, 2-trichloroethanol	(b) trichloromethanol
(c) 2, 2, 2-trichloropropanol	(d) chloroform

(iv) Which of the following reaction will not result in the formation of carbon-carbon bonds?

(a) Cannizzaro reaction	(b) Wurtz reaction
(c) Reimer- Tiemann reaction	(d) Friedel-Crafts acylation

Read the passage given below and answer the following questions:
The addition reaction of enol or enolate to the carbonyl functional group of aldehyde or ketone is known as aldol addition. The \(\beta\)-hydroxyaldehyde or \(\beta\)-hydroxyketone so obtained undergo dehydration in second step to produce a conjugated enone. The first part of reaction is an addition reaction and the second part is an elimination reaction. Carbonyl compound having \(\alpha\)-hydrogen undergoes aldol condensation reaction.

The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Condensation reaction is the reverse of which of the following reaction?

(a) Lock and key hypothesis	(b) Oxidation
(c) Hydrolysis	(d) Glycogen formation

(ii) Which of the following compounds would be the main product of an aldol condensation of acetaldehyde and acetone?

(a) CH₃CH=CHCHO	(b) CH₃CH=CHCOCH₃
(c) (CH₃)₂C=CHCHO	(d) (CH₃)₂C=CHCOCH₃

(ii) Which combination of carbonyl compounds gives phenyl vinyl ketone by an aldol condensation?

(a) Acetophenone and Formaldehyde	(b) Acetophenone and acetaldehyde
(c) Benzaldehyde and acetaldehyde	(d) Benzaldehyde and acetone

(iv) Which of the following will undergo aldol condensation?

(a) HCHO	(b) CH₃CH₂OH
(c) C₆H₅CHO	(d) CH₃CH₂CHO

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Answers Key:

Case Study Questions

5 x 4 = 20

(i) (a): Iodoform test is given by the organic compounds having

C₆H₅ - CH₂-OH : Benzyl alcohol
Therefore, isopropyl alcohol will give positive iodoform test.
(ii) (b): Iodoform reaction of acetone occurs in following steps

(iii) (c): Given reagents indicate the presence of -COCH₃ group in the starting compound A. Further, since the -COOH group introduced in B due to iodoform reaction is absent in the final product, B should be a p-keto acid. Hence, A should have structure given in option (c).

(iv) (c): Since compound A(C₃H₆O) undergoes iodoform test, it must be CH₃COCH₃ (propanone). Further, the compound 'B' obtained from 'A' has three times more the number of carbon atoms as in 'A' (propanone), 'B' must be phorone, i.e., 2,6-dimethyl-2, 5-heptadien -4-one.
\(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{C}=\mathrm{O}+\mathrm{H}_{3} \mathrm{CCOCH}_{3}+\mathrm{O}=\mathrm{C}\left(\mathrm{CH}_{3}\right)_{2}\) \(\stackrel{\mathrm{HCl}}{\rightarrow}\left(\mathrm{CH}_{3}\right)_{2} \mathrm{C}=\mathrm{CHCOCH}=\mathrm{C}\left(\mathrm{CH}_{3}\right)_{2}\)
A, propanone(3 molecules) 2,6-dimethyl- 2,5-heptadien-4-one

(i) (d): All the reactions are showing the acidic properties of carboxylic acid. Carboxylic acid forms the sodium salts with all i.e., alkali metals, NaOH and Na₂CO₃ etc. and removes the acidic proton from the carboxylic acid.
(ii) (a): In general, greater the +I effect of the group attached to the carboxyl group, lesser will be the acidic strength and greater the -I effect ofthe group, greater will be acidic strength. As number of halogen atoms and electronegativity of halogen atom increases, acidic strength increases. Thus, correct order of acidic strength is
CF₃COOH> CHCl₂COOH > HCOOH > C₆H₅CH₂COOH > CH₃COOH
(iii) (c) : Stronger -I group attached closer to - COOH makes the acid stronger, i.e., acid has the larger dissociation constant. - Br shows poor (-I) effect and also far away from -COOH group i.e., option (c) has smallest dissociation constant.
(iv) (a): Due to ortho-effect, (I) and (II) are stronger acids than (III) and (IV). Due to two ortho-hydroxyl groups in (I), it is stronger acid than (II). (III) is a stronger acid than (IV) because at m-position, -OH group cannot exert its +R effect but can only exert its -I effect while at p-position, -OH group exerts its strong +R effect. Thus, the correct order of acidity is : I > II > III > IV.

(iv) (b)

(i) (a): It is an example of cross Cannizzaro reaction where aromatic aldehyde gets reduced to alcohol and aliphatic aldehyde gets oxidised to its sodium salt (both aldehydes must not contain any \(\alpha\)-hydrogen).

(ii) (c)
(iii) (a): The Cannizzaro product of given reaction yields 2, 2, 2-trichloroethanol.

(iv) (a): C-C bond is not formed in Cannizzaro reaction while other reactions result in the formation of C-C bond.

(i) (c) : Condensation reaction is the reverse of hydrolysis, which splits a chemical entity into two parts through the action of the polar water molecule

(iii) (a)
(iv) (d)